半导体纳米颗粒在脉冲激光下的升温研究

No abstract available

No abstract available

Fluence curves are a powerful tool for understanding the mechanisms underlying nanosecond pulse laser heating of aerosolized nanoparticles, which is relevant to laser-induced incandescence (LII). This paper presents analytical expressions encompassing the entirety of the fluence domain considered in LII and uses them to formally define fluence regimes. The derived expressions and non-dimensional parameters facilitate one of the first comparisons of published experimental fluence curves. This procedure provides physical insight into the laser-nanoparticle interaction and highlights inconsistencies in the application of LII models to analyze the data.

Pulsed laser irradiation with an appropriate laser fluence (50–200 mJ pulse−1 cm−2) onto photo‐absorptive ceramic or metallic nanoparticles dispersed in liquid can induce a rapid rise in the local temperature to 1000–3000 K of the particles, instantaneous generation of melt droplets, and formation of spherical particles of high‐temperature materials via quenching. Such space‐selective pulsed heating through optical absorption may enable reactive powder processing through mimicking of conventional high‐temperature ceramic or metallurgical‐reaction processes. Here, by combining photo‐absorptive ZnO and non‐photo‐absorptive MgO as raw particles, the laser irradiation technique for high‐temperature powder reaction was applied to check whether submicrometer spherical ZnO–MgO solid‐solution particles can be generated. Various raw‐particle mixtures obtained by mechanical milling, coprecipitation from inorganic salts, and thermolysis of organic salts were tested; the produced particles were characterized to reveal the effects of temperature on the composition of MgO included in ZnO host crystals. The raw‐particle mixtures composed of small particles tended to transform into ZnO–MgO particles with high MgO content. Physicochemical calculations and experimental results revealed the importance of appropriate particle sizes of photo‐absorptive ZnO and non‐photo‐absorptive MgO, their mutual close contact, and laser irradiation conditions in the reactive fabrication of ZnO–MgO submicrometer particles.

The interaction of x-ray pulses with metallic and semiconductor materials has a wide range of applications in defense, nuclear fusion, and material processing. As such, thermal analysis of x-ray interactions with materials is crucial, particularly for ultrashort and short pulses (ranging from femtoseconds to a few nanoseconds). Similar to optical lasers, pulsed x rays can induce melting, evaporation, and ablation of materials through various physical mechanisms. A two-temperature model (TTM) is developed and applied to investigate the effects of soft x rays on the heating, melting, and ablation of metallic and semiconductor materials, which are commonly used in spacecraft solar cells, fusion devices, and high-energy physics applications. This model is particularly suited for analyzing these processes at very short time scales. The applicability of TTM for x-ray pulses lasting a few nanoseconds is also explored. The results are validated against the experimental data, offering valuable insights into the electron-lattice dynamics in metals and semiconductors during and after exposure to x-ray pulses.

No abstract available

We report the fabrication of metal alloy Au–Pd nanoparticles on semiconductor thin film substrates (ZnO) by laser-induced dewetting. Employing a UV excimer laser, a single pulse was directed onto a three-layer film stack on a glass substrate: glass/ZnO/Au/Pd and glass/ZnO/Pd/Au. We simulated the temperature attained by the thin films enabling the prediction of energy thresholds required for melting the metal films but avoiding modifying the ZnO film. A specific range is reported of the pulse energy conducive to nanoparticle formation and the energy threshold required to modify the ZnO film beneath them. Depending on the pulse energy applied, the mean diameter of the nanoparticles varied from approximately 150 to around 70 nm. Notably, higher fluences resulted in smaller particles but also induced surface cracks in the ZnO film. Additionally, we observed a reduction in nanoparticle size with increased Pd content. Our results show that laser-induced dewetting can produce bimetallic alloy nanoparticles and, at the same time, ensure the preservation of the optical properties of the ZnO film. This approach opens avenues for tailoring material characteristics and expanding the range of applications of metal nanoparticles on semiconductor-based systems.

We develop a model describing non-equilibrium processes under the excitation of resonant semiconductor nanostructures with ultrashort laser pulses with a duration of about 100 fs. We focus on the heating effects related to pulsed excitation with account on free carriers generation, thermalization, and relaxation. The heat exchange between the electron and phonon system is treated within the two-temperature model. We applied the developed model to describing pulsed heating of silicon nanocylinder on top of a dielectric substrate. We come up with estimations of the thermal damage threshold of the considered structures which provides the limits for the experimental conditions and ensures thermal stability of the samples.

No abstract available

The ZnO/noble metal (both individually - Ag or Pd and in combination) nanocomposites are prepared by laser synthesis methods at atmospheric pressure in air. The formation of complex porous  nanostructures is carried out by picosecond pulsed laser deposition at room temperature. The effect of post-deposition nanosecond laser annealing on the morphology and optical properties of the nanostructures is studied. The contribution of laser modifications to the change of a surface plasmon resonance (SPR) absorption band, and respectively, to the near-band-edge (NBE) and deep-level photoluminescence emission (DL), is investigated. The resonance absorption properties are obtainedfor Ag/ZnO nanostructures before and after the laser annealing. While the SPR absorption band appears for mono- and bimetallic samples with palladium after the laser annealing. The plasmon resonance absorption contributes to the enhancement of photoluminescence band-edge UV emission of all samples and suppression of the strong Vis DL emission of monometallic noble metal/ZnO  nanocomposites after the annealing. The low level of the DLE emission is observed before the  annealing of the bimetallic sample Ag-Pd/ZnO, with annealing slightly affecting it. This sample demonstrates significantly smaller nanoparticles (NPs), as well as a narrower size distribution in  comparison to monometallic noble metal/ZnO nanocomposites. 

Nanosecond ultraviolet (UV) laser annealing at wavelengths of 355 nm and below has emerged as a versatile solution for advanced material processing, offering precise control over thin‐film modification while minimizing thermal damage to underlying substrates. By delivering high‐energy pulses, UV nanosecond annealing enables localized heating and rapid quenching, which promotes defect passivation, crystallization, and conductivity enhancement in semiconductors and transparent conductive oxide layers. This technique is particularly advantageous for temperature‐sensitive applications such as flexible electronics, solar cells, and display technologies, where conventional furnace annealing is unsuitable. Studies demonstrate that nanosecond UV laser annealing significantly improves the electrical performance of amorphous oxide semiconductors, reduces sheet resistance in transparent conductive films, and enhances device stability without compromising substrate integrity. The short‐wavelength UV light ensures strong absorption in thin films, allowing efficient energy transfer and selective processing. Moreover, the scalability and compatibility of this method with industrial manufacturing make it a promising candidate for next‐generation optoelectronic devices. Today, nanosecond UV laser annealing solutions provide a high‐throughput, noninvasive, and cost‐effective pathway to engineer material properties at the nanoscale. Their ability to combine precision with efficiency positions them as enabler in the development of high‐performance and energy‐efficient electronic systems on wafers and panels.

Tissue local temperature information is necessary for guiding energy-based medical treatments. In cancer treatments such as thermal therapy, heating is applied to local tissue to kill the tumor cells. These techniques require a temperature monitoring device with high sensitivity. In this Letter, we demonstrate a pulsed-laser-diode-(PLD)-based photoacoustic temperature sensing (PATS) system for monitoring tissue temperature in real time. The system takes advantage of a high repetition rate (7000 Hz), a near-infrared wavelength (803 nm), and a relatively high energy 1.42 mJ/pulse laser. The system is capable of providing local temperature information at high temporal resolution of 1 ms and high sensitivity of 0.31°C. The temperature data measured with a PLD-PATS system are compared with the data provided by the commercial fiber Bragg grating sensor. The proposed system will find applications in radio-frequency ablation, photothermal therapy, and focused ultrasound, etc., used for cancer treatments.

The ultraprecision machining of diamond presents certain difficulties due to its extreme hardness. However, the graphitization modification can enhance its machinability. This work presents an investigation into the characteristics of the graphitization modification in polycrystalline diamond induced by a nanosecond pulsed laser. In this paper, the morphology of microgrooves under laser modification was observed, material deposition and graphitization in different regions were researched, and the regularities of microgrooves at different laser powers were obtained. A molecular dynamics (MD) simulation was carried out to reveal the mechanism behind graphitization modification; when the pulse laser acts on the diamond surface and the temperature rises to the critical temperature of graphitization, the graphite crystal nuclei form and grow, resulting in the graphitization modification. It was confirmed that the existence of grain boundaries (GBs) contributed to the graphitization of polycrystalline diamond during laser modification. It was predicted that a lower laser power could cause a higher proportion of graphitization. The results of ablation thresholds and the effect of the defocusing position on the graphitization of diamond showed that for a fixed laser power, the highest graphitization ratio could be obtained when the defocusing quantity was optimized. Finally, the results of precision grinding experiments verified the feasibility of using laser graphitization pretreatment to improve the efficiency and quality of precision grinding.

Dry reforming of methane (DRM) is a highly endothermic process, with its development hindered by the harsh thermocatalytic conditions required. We propose an innovative DRM approach utilizing a 16 W pulsed laser in combination with a cost-effective Mo2C catalyst, enabling DRM under milder conditions. The pulsed laser serves a dual function by inducing localized high temperatures and generating *CH plasma on the Mo2C surface. This activates CH4 and CO2, significantly accelerating the DRM reaction. Notably, the laser directly generates *CH plasma from CH4 through thermionic emission and cascade ionization, bypassing the traditional step-by-step dehydrogenation process and eliminating the rate-limiting step of methane cracking. This method maintains a carbon-oxygen balanced environment, thus preventing the deactivation of the Mo2C catalyst due to CO2 oxidation. The laser-catalytic DRM achieves high yields of H2 (14300.8 mmol h−1 g−1) and CO (14949.9 mmol h−1 g−1) with satisfactory energy efficiency (0.98 mmol kJ−1), providing a promising alternative for high-energy-consuming catalytic systems. Dry reforming of methane (DRM) is a highly endothermic process, often limited by the severe thermocatalytic conditions it demands. Here the authors introduce a novel DRM method that employs a 16 W pulsed laser along with a cost-effective Mo2C catalyst, allowing DRM to proceed under milder conditions.

Pulsed laser melting in liquid (PLML) is a technique to fabricate spherical submicrometer particles (SMPs) wherein nanosecond pulsed laser (several tens to several hundreds of mJ pulse -1 cm -2 ) irradiates raw particles dispersed in liquid. Raw particles are transiently heated above the melting point to form spherical particles, which enables pulsed heating of surrounding liquid to form thermally induced bubbles by liquid vaporization. These transient bubbles play an important role as a thermal barrier to rapidly heat the particle. Reduced SMPs are generated from raw metal-oxide nanoparticles by PLML process in ethanol. This reduction cannot be explained by high-temperature thermal decomposition, but by mediation of molecules decomposed from ethanol. Computational simulations of ethanol decomposition by pulsed heating for 100 ns at the temperature 1000-4000 K revealed that ethylene is generated as the main product. Gibbs free energies of oxide reduction reactions mediated by ethylene greatly decreased compared to those without ethylene mediation. This explanation can be applied to reductive SMP formation from various transition metal oxides by PLML.

Pulsed laser melting in liquid (PLML) is a technique to produce submicrometer spherical particles (SMPs). In this process, raw particles dispersed in liquid are selectively heated, and thermally induced nanobubbles (TINBs) at the particle surface are generated and act as a thermal barrier to enhance the temperature increase during heating. However, monitoring TINBs is difficult since PLML is a low-temperature, nonplasma process. Simple transmittance measurements of monodisperse Au SMP (250 nm) colloidal solutions on a transient time scale were used to monitor the temporal dependence of the TINB thickness and the pressure within the bubble. By applying this technique for ZnO and Sn SMP formation, TINBs in the PLML process are important in promoting the formation of large particles via particle merging during laser heating.

No abstract available

In Raman analysis of aerosol, collected particles often exhibit loose structures that make them susceptible to laser-induced heating and thermal artifacts. This study evaluated the impact of laser power, sample thickness, and integration time on the Raman spectra of metal oxide, carbonaceous, and semiconductor powders, with particular attention to thermal effects. Temperature-dependent spectra were also acquired from 30 °C to 450 °C. The results indicated increasing laser power and integration time amplified signal intensity but led to ablation pits in thicker Cr2O3 and multiwall carbon nanotubes. In contrast, thinner samples maintained distinct characteristic bands even at a laser power of 500 mW. Temperature-dependent Raman measurements further showed reduced peak intensities of all materials with increasing temperature. For monocrystalline silicon, the Raman peak position exhibited a linear redshift with temperature. Additionally, finite element method (COMSOL Multiphysics) was employed to simulate the temperature distribution under varying laser powers and sample thicknesses. The simulations demonstrated temperature rise within 800 ms and showed good agreement with experimental results. Finally, the optimal strategies that maintain spectral integrity while minimizing thermal artifacts were proposed, along with corresponding computational formulas and optimization examples.

Thermal contributions are typically ignored in optical spectroscopy of semiconductor nanomaterials. However, such considerations are important for an accurate interpretation of spectroscopy measurements. Here, we identify signatures of transient photoinduced heating in optical pump-probe signals of colloidal semiconductor nanocrystal films. We find that lattice heating following excitation above the bandgap or at high fluences leads to a significant temperature-induced transient signal that impacts three aspects of pump-probe measurements: the transient spectra, relaxation kinetics, and spatiotemporally resolved carrier diffusivity. The effects are general across nanocrystal core material, appearing in both CdSe and PbS quantum dot films. This study proposes several methods for distinguishing simultaneous electronic and thermal contributions to transient measurements as well as guidelines for how to avoid misassignments. On the other hand, we discuss the ability to track both electronic and thermal transport as a largely missed opportunity that can be leveraged.

We demonstrate that laser peening coupled with sintering of CdTe nanowire films substantially enhances film quality and charge transfer while largely maintaining basic particle morphology. During the laser peening phase, a shockwave is used to compress the film. Laser sintering comprises the second step, where a nanosecond pulse laser beam welds the nanowires. Microstructure, morphology, material content and electrical conductivities of the films are characterized before and after treatment. The morphology results show that laser peening can decrease porosity and bring nanowires into contact and pulsed laser heating fuses those contacts. Multiphysics simulations coupling electromagnetic and heat transfer modules demonstrate that during pulsed laser heating, local EM field enhancement is generated specifically around the contact areas between two semiconductor nanowires, indicating localized heating. The characterization results indicate that solely laser peening or sintering can only moderately improve the thin film quality; however, when coupled together as laser peen sintering (LPS), the electrical conductivity enhancement is dramatic. LPS can decrease resistivity up to a factor of ~10,000, resulting in values on the order of ~105 Ω-cm in some cases, which is comparable to CdTe thin films. Our work demonstrates that LPS is an effective processing method to obtain high-quality semiconductor nanocrystal films.

This paper demonstrates that free-standing silicon nanocrystals (Si NCs) have significantly different thermal conductivity properties compared to Si NCs embedded in a host matrix. The temperatures of Si NCs under laser illumination have been determined by measuring the ratio of the Anti-Stokes to Stokes intensities of the first order Si-Si transverse optical (TO) phonon mode. It is found that large free-standing Si NCs are easily heated up to ∼953 K by the laser light. The laser heating effects are reversible to a large extent, however the nature of the free-standing Si NCs is slightly modified after intensive illumination. The free-standing Si NCs can even be easily melted when exposed to a well-focused laser beam. Under these conditions, the blackbody radiation of the heated Si NCs starts to compete with the detected Raman signals. A simplified model of the heating effects is proposed to study the size dependence of the heated free-standing Si NCs with increasing laser power. It is concluded that the huge red-shift of the Si-Si TO mode observed under intensive laser illumination originates from laser-induced heating effects. In contrast, under similar illumination conditions Si NCs embedded in matrixes are hardly heated due to better thermal conductivity.

Laser direct writing (LDW) offers a powerful, mask‐free, and straightforward route for fabricating high‐resolution, luminescent microarrays of lead halide perovskite nanocrystals (LH PNCs) within polymer films. However, when prepared from conventional halide salt precursors, the low intrinsic formation energy of ionic LH PNCs renders them highly susceptible to thermally induced erasing, severely limiting their practical utility. To overcome this limitation, we introduce halogenated organic compounds (R‐X) as the halogen source. Irradiation with a high photon energy 355 nm nanosecond laser directly cleaves the C─X bond, releasing halide anions that initiate the in situ nucleation and growth of LH PNCs within the polymer matrix. This strategy enables the rapid fabrication of multicolour luminescent LH PQD microarrays across a broad range of polymer substrates, while effectively suppressing thermal erasing that they retain their structural integrity even after heating to 120°C, whereas analogous microarrays fabricated from halide salts erased at only 50°C. Leveraging this exceptional stability together with the design versatility of LDW, we further demonstrate the creation of mesoscopic fluorescent anti‐counterfeiting labels such as those embedded in express packaging, highlighting the potential for scalable, secure, and multifunctional photonic applications.

A series of compounds with the general formula (La1−xREx)2Ti2O7 (x = 0.005, 0.015, and 0.025) doped with Yb3+, Er3+, and Tm3+ rare earth ions were prepared by the traditional solid-state reaction at 1350°C for 24 h. The X-ray powder diffraction technique, high-resolution transmission electron microscopy, and photoluminescence spectroscopy technique were used to characterize the structure and optical properties of the compounds. All compounds showed a single-phase orthorhombic structure with a space group Pna21, as confirmed by JCPDS (Cart No: 01-070-1690). The La1.9Yb0.04Er0.01Tm0.05 Ti2O7 nanocrystals exhibited intense tunable white light luminescence signals in the full spectrum, and green and blue emissions were predominant in the Yb3+/Er3+- and Yb3+/Tm3+-doped titanates, respectively. In this study, the influence of concentration and excitation power on the upconversion luminescence, color, and calculated laser-power-induced heating performance of La2Ti2O7 nanophosphors were investigated at room temperature.

No abstract available

Three-dimensional (3D) laser nanoprinting allows maskless manufacturing of diverse nanostructures with nanoscale resolution. However, 3D manufacturing of inorganic nanostructures typically requires nanomaterial-polymer composites and is limited by a photopolymerization mechanism, resulting in a reduction of material purity and degradation of intrinsic properties. We developed a polymerization-independent, laser direct writing technique called photoexcitation-induced chemical bonding. Without any additives, the holes excited inside semiconductor quantum dots are transferred to the nanocrystal surface and improve their chemical reactivity, leading to interparticle chemical bonding. As a proof of concept, we printed arbitrary 3D quantum dot architectures at a resolution beyond the diffraction limit. Our strategy will enable the manufacturing of free-form quantum dot optoelectronic devices such as light-emitting devices or photodetectors. Description Photoprinting nanoparticles Nanoparticle assembly often requires tailored selection of the ligands so that they can selectively bond, as with complementary DNA strands. Alternately, they can be linked together at specified locations using photopolymerization to connect ligands at desired places. However, this process adds to the complexity of making the nanoparticles and is limited by the fidelity of the ligand attachment. Liu et al. show that light can be used to desorb surface thiolate ligands from cadmium selenide/zinc sulfide core shell quantum dots (see the Perspective by Pan and Talapin). The resulting trapped holes drive bonding between the particles through the remaining surface ligands. The authors reveal photoprinting of arbitrary three-dimensional architectures at a resolution beyond the diffraction limit and for a range of nanocrystals. Printing can be optically selected based on the size and/or bandgap of the quantum dots. —MSL Photoexcitation-induced chemical bonding enables high-resolution three-dimensional printing of semiconductor quantum dots.

This study introduces an innovative photo-thermoacoustic-diffusion model to explore wave propagation in a hydro-poroelastic semiconductor medium under laser excitation. The model combines photothermal transport principles with mass diffusion and poroelasticity, capturing the interconnected effects of thermal, chemical, and carrier diffusion processes induced by laser heating. Analytical solutions for the primary physical fields within the medium are obtained using the normal mode analysis method. By incorporating the distinctive properties of hydro-semiconductors, such as fluid-saturated pore interactions, the model is particularly suited for studying porous semiconductor materials. The interaction of photo-induced thermal and mechanical waves with diffusion processes is analyzed under specific boundary conditions. Graphical representations of numerical results highlight the influence of critical parameters, showcasing the model's effectiveness in advancing material understanding and optimization, with potential applications in optoelectronics, photothermal therapy, and semiconductor device design.

With the increasing availability of scanning laser systems and direct laser writing and lithography equipment, investigations of laser modification of materials regain their high relevance for both emerging and well-established semiconductors, such as Si. In this work, we have used Raman spectroscopy to study the structural modification of amorphous Si (aSi), polycrystalline Si (polySi), Si nanocrystals embedded in a SiO2 matrix (ncSiSiO2), as well as SiO2/Si/SiO2 multilayer structures, subjected to 1064 nm pulsed laser annealing (PLA) by a commercial scanning laser engraver. Raman scattering spectroscopy was the main technique for probing the induced structural changes due to its high sensitivity to phonon peak parameters, structural disorder, and strain. Comparison of the spectra measured at different excitation wavelengths allows probing of the annealed structures at various depths. For aSi, PLA induces local formation of highly crystalline Si patterns, exhibiting a threshold effect with abrupt spectral changes at small (2–3%) variations of PLA power. For SiO2/Si/SiO2 multilayers with different combinations of layer thicknesses, PLA results in relaxation to a state that no longer depends on initial Si and SiO2 layer thicknesses.

Synthesis of metallic-semiconductor nanocomposite based on ZnO nanowires under pulse-periodic laser action with a pulse frequency of 3 Hz was performed. By analyzing the results of the samples’ responses to the laser-induced vibroexcitation, it was found that the vibration rate increases in the case of frequencies that are divisible by the frequency of initial oscillation, during the amplitude decrease with the frequency increase. The determination of sample heating features by laser action was performed. Analysis of the X-ray diffraction image showed that thermal oxidation by the pulse-periodic laser treatment leads to the ZnO oxide formation on the substrate of porous Cu–Zn alloy. It is shown that a non-stationary local deformation, caused by a highly-powered external action, is a condition for the intensification of mass transfer in the solid phase of a metallic material. Thus, for the first time it is shown that the use of synergies of thermal effects and laser-induced vibrations in the sound frequency range of pulse-periodic laser beam allow the implementation of a new approach for the creation of structures of composite nanomaterials based on zinc oxide. Results of study are the basis for creating software to controlling laser systems.

Multimodal therapy is an emerging medical intervention to overcome the current limitation in cancer therapy combining treatment modalities with different mechanisms of action to eradicate tumors. This study demonstrates a targeted multifunctional bovine serum albumin (BSA)-functionalized CuFeS2/chlorin e6 (Ce6) for synergistic photothermal therapy (PTT) and photodynamic therapy (PDT) effects. The CuFeS2 nanocrystals were synthesized through a simple heating-up approach and transferred into an aqueous phase using BSA in an ultrasonic-assisted microemulsion method. The as-prepared CuFeS2@BSA nanoparticles further conjugated with folic acid (FA) followed by attachment of Ce6 to form the Ce6:CuFeS2@BSA-FA nanohybrid with improved solubility and strong near-infrared (NIR) absorbance and fluorescence. It is the first report to fabricate the targeted Ce6:CuFeS2@BSA-FA hybrid and evaluates their synergistic PTT/PDT effect using a single laser. The Ce6:CuFeS2@BSA-FA hybrid showed lower toxicity in vitro (HeLa and HepG2 cells) and in vivo (zebrafish embryos), while they are selectively recognized and internalized by HeLa cells that over-express folate receptors. Compared to each modality applied separately, the combined single-laser-induced PTT and PDT treatment showed the enhanced generation of heat and reactive oxygen species (ROS) with synergistic cancer killing under 671 nm laser irradiation (10 min, 1 W/cm2). As a biocompatible targeted nanoprobe, the multifunctional nanohybrid holds promise in combined PDT/PTT synergistic therapy to achieve better efficacy.

Ultrafast laser processing was applied for the synthesis of semiconductor nanostructures with finely tunable chemical composition and plasmonic properties that were further employed for laser-induced hyperthermia with variable heating efficiency. © 2024 The Author(s)

Semiconductor nanowire production through vapor- and solution-based processes has propelled nanowire systems toward a wide range of technological applications. Although vapor-based nanowire syntheses enable precise control over nanowire composition and phase, they typically employ batch processes with specialized pressure management systems, limiting throughput. Solution-based nanowire growth processes have improved scalability but can require even more extensive pressure and temperature management systems. Here, we demonstrate a solution-based nanowire growth process that utilizes the large Young-Laplace interfacial surface pressures and collective heating effects of colloidal metal nanocrystals under irradiation to drive nanowire growth photothermally. Laser irradiation of a solution containing metal nanocrystals and semiconductor precursors facilitates rapid heating, precursor decomposition, and nanowire growth on a benchtop in simple glassware under standard conditions, potentially enabling a range of solution-based experiments including in-line combinatorial identification of optimized reaction parameters, in situ measurements, and the production of nanowires with complex compositions.

Plasmonic nanocomposites with efficient multi-band blue photoluminescence were designed using different IV group semiconductors (Si; SiC; C; Ge). Various ultrafast laser-processing approaches strongly affected their emission, plasmonic properties and fs laser-induced heating of colloidal solutions.

No abstract available

Ultrashort pulsed laser annealing is an efficient technique for crystallizing amorphous semiconductors with the possibility to obtain polycrystalline films at low temperatures, below the melting point, through non-thermal processes. Here, a multilayer structure consisting of alternating amorphous silicon and germanium films was annealed by mid-infrared (1500 nm) ultrashort (70 fs) laser pulses under single-shot and multi-shot irradiation conditions. We investigate selective crystallization of ultrathin (3.5 nm) a-Ge non-hydrogenated films, which are promising for the generation of highly photostable nanodots. Based on Raman spectroscopy analysis, we demonstrate that, in contrast to thicker (above 10 nm) Ge films, explosive stress-induced crystallization is suppressed in such ultrathin systems and proceeds via thermal melting. This is likely due to the islet structure of ultrathin films, which results in the formation of nanopores at the Si-Ge interface and reduces stress confinement during ultrashort laser heating.

Ultrafast laser processing possesses unique outlooks for the synthesis of novel nanoarchitectures and their further applications in the field of life science. It allows not only the formation of multi-element nanostructures with tuneable performance but also provides various non-invasive laser-stimulated modalities. In this work, we employed ultrafast laser processing for the manufacturing of silicon–gold nanocomposites (Si/Au NCs) with the Au mass fraction variable from 15% (0.5 min ablation time) to 79% (10 min) which increased their plasmonic efficiency by six times and narrowed the bandgap from 1.55 eV to 1.23 eV. These nanostructures demonstrated a considerable fs laser-stimulated hyperthermia with a Au-dependent heating efficiency (~10–20 °C). The prepared surfactant-free colloidal solutions showed good chemical stability with a decrease (i) of zeta (ξ) potential (from −46 mV to −30 mV) and (ii) of the hydrodynamic size of the nanoparticles (from 104 nm to 52 nm) due to the increase in the laser ablation time from 0.5 min to 10 min. The electrical conductivity of NCs revealed a minimum value (~1.53 µS/cm) at 2 min ablation time while their increasing concentration was saturated (~1012 NPs/mL) at 7 min ablation duration. The formed NCs demonstrated a polycrystalline Au nature regardless of the laser ablation time accompanied with the coexistence of oxidized Au and oxidized Si as well as gold silicide phases at a shorter laser ablation time (<1 min) and the formation of a pristine Au at a longer irradiation. Our findings demonstrate the merged employment of ultrafast laser processing for the design of multi-element NCs with tuneable properties reveal efficient composition-sensitive photo-thermal therapy modality.

Facile synthesis of multi-modal nanostructures is still a challenging task for many applications, especially in the field of healthcare. Ultrafast laser processing offers a great opportunity of merging different elements into one nanoparticle using highly pure chemical conditions. However, synthesis of multi-element nanoparticles by pulsed laser ablation is usually limited by 2-3 chemical elements. In this work, we applied various approaches of this technique such as direct laser ablation and laser co-fragmentation to synthesize silicon-metallic nanocomposites containing 8 plasmonic and magnetic metallic elements. We found significant (~2.1-fold) reduction of hydrodynamic size after such treatment accompanied with some changes of ξ-potential values. ICP-MS study revealed a considerable contribution (from 2.0 µg/mL of Ni to 10.4 µg/mL of Pt in the nanocomposites) from all 8 metallic elements in the resulted multi-element nanocomposites. These nanostructures containing 8 metals had a lower photoluminescence intensity due to a weaker absorption. At the same time, their fs laser-induced heating demonstrated ~1.9-fold better efficiency in comparison with pristine silicon nanoparticles. These findings demonstrate an easy way of synthesizing of multi-element nanocomposites in chemically pure conditions for their multi-modal healthcare applications.

Although non-toxic nanoscale materials are widely employed for different healthcare applications, their performance is still considerably limited. In this paper, various approaches using the environmentally friendly ultrafast laser processing were employed to remodel IV group semiconductor nanostructures and synthesize highly-stable (ξ-potential is up to -47 mV) colloidal solutions of plasmonic (525 nm) nanocomposites with a strong size-dependent chemical content. All nanocomposites exhibited a remarkable lamp-excited multi-band blue emission centred at around 420 nm that is considerably (∼10-fold for Au-SiC) stronger than from nanocomposites prepared by the laser co-fragmentation technique. The latter formed a greater quantity of smaller narrowly dispersed (∼4 nm for Au-Si) plasmonic nanostructures compared to the direct laser ablation method. Moreover, it led to a greater number of semiconductor elements (∼1.7-fold for Au-Ge) in the nanocomposites, which was correlated with lower (∼30%) electrical conductivity. Aqueous colloidal solutions revealed a greater degree (∼80%) of the femtosecond laser-induced heating for all nanocomposites formed by direct laser ablation. These findings highlight the peculiarities of the applied laser processing approaches and considerably facilitate the design of specific multi-modal plasmonic-fluorescence (biosensing, bioimaging, hyperthermia) nanocomposites with a required performance that significantly expands the application area of semiconductor nanostructures.

No abstract available

The results of direct femtosecond laser structuring of GaAs wafer coated with continuous semitransparent gold (Au) film are presented. The obtained structures demonstrate a combination of different features, namely laser-induced periodic surface structures (LIPSS) on semiconductor and metal film, nanoparticles, Au islands, and fragments of exfoliated Au film. The properties of Au-GaAs samples are studied with scanning electron microscopy (SEM), Raman scattering, and photoluminescence (PL) spectroscopy. The behaviour of phonon modes and enhancement of band-edge PL of Au-GaAs composite sample are discussed. The Raman spectra of Au-GaAs sample processed at different levels of irradiation pulse energy reveal forbidden TO and allowed LO phonon modes for selected geometry of experiment, as well as the manifestation of GaAs surface oxidation and amorphization. A 12-fold increase of PL intensity for Au-GaAs sample with LIPSS compared to initial GaAs surface is observed. The detected PL enhancement is caused by an increase of absorption in GaAs due to the light field enhancement near the Au nanoislands and a decrease of nonradiative surface recombination. The blue shift of PL band is caused by the quantum size effect in GaAs nano-sized features at laser processed surface. The combination of GaAs substrate with surface micro- and nanostructures with Au nanoparticles can be useful for photovoltaic and sensorics applications.

Spin crossover (SCO) is a promising switching phenomenon when implemented in electronic devices as molecules, thin films or nanoparticles. Among the properties modulated along this phenomenon, optically induced mechanical changes are of tremendous importance as they can work as fast light‐induced mechanical switches or allow to investigate and control microstructural strains and fatigability. The development of characterization techniques probing nanoscopic behavior with high spatio‐temporal resolution allows to trigger and visualize such mechanical changes of individual nanoscopic objects. Here, ultrafast transmission electron microscopy (UTEM) is used to precisely probe the length changes of individual switchable nanoparticles induced thermally by nanosecond laser pulses. This allows revealing of the mechanisms of spin switching, leading to the macroscopic expansion of SCO materials. This study is conducted on individual pure SCO nanoparticles and SCO nanoparticles encapsulating gold nanorods that serve for plasmonic heating under laser pulses. Length changes are compared with time‐resolved optical measurements performed on an assembly of these particles.

Expanding the activity of wide bandgap semiconductors from the UV into the visible range has become a central goal for their application in green solar photocatalysis. The hybrid plasmonic/semiconductor system, based on silver nanoparticles (Ag NPs) embedded in a film of CeO2, is an example of a functional material developed with this aim. In this work, we take advantage of the chemical sensitivity of free electron laser (FEL) time-resolved soft X-ray absorption spectroscopy (TRXAS) to investigate the electron transfer process from the Ag NPs to the CeO2 film generated by the NPs plasmonic resonance photoexcitation. Ultrafast changes (<200 fs) of the Ce N4,5 absorption edge allowed us to conclude that the excited Ag NPs transfer electrons to the Ce atoms of the CeO2 film through a highly efficient electron-based mechanism. These results demonstrate the potential of FEL-based TRXAS measurements for the characterization of energy transfer in novel hybrid plasmonic/semiconductor materials.

A major challenge in nanotechnology is the fabrication of complex three-dimensional (3D) structures with desired materials. We present a strategy for fabricating arbitrary 3D nanostructures with a library of materials including metals, metal alloys, 2D materials, oxides, diamond, upconversion materials, semiconductors, polymers, biomaterials, molecular crystals, and inks. Specifically, hydrogels patterned by femtosecond light sheets are used as templates that allow for direct assembly of materials to form designed nanostructures. By fine-tuning the exposure strategy and features of the patterned gel, 2D and 3D structures of 20- to 200-nm resolution are realized. We fabricated nanodevices, including encrypted optical storage and microelectrodes, to demonstrate their designed functionality and precision. These results show that our method provides a systematic solution for nanofabrication across different classes of materials and opens up further possibilities for the design of sophisticated nanodevices. Description Making many tiny things Fabricating high-resolution and complex objects with additive manufacturing across a wide range of materials is challenging. Han et al. synthesized very finely detailed objects from a wide range of materials using femtosecond light sheets and nanoparticle-laden hydrogels. The strategy works for ceramics, polymers, metals, semiconductors, and other materials while still maintaining fine feature sizes. This technique could enable nanofabrication across different classes of materials. —BG Femtosecond light sheets can be used to assemble a wide range of materials into very small three-dimensional structures.

In this work, we report the discovery and cation exchange‐mediated synthesis of Cu2FeS2, a compound predicted computationally but never observed in nature or realized in the laboratory. Our findings reveal that it possesses an anomalous electronic structure among analogous Cu‐Fe‐S semiconductors due to the unique valence configuration. More strikingly, this unprecedented material displays ultrahigh molar extinction coefficients (ε > 107 M−1 cm−1) throughout the visible to near infrared (NIR) spectrum arising from remarkable localized surface plasmon resonances (LSPRs), coupled with intense electron‐phonon interactions that enable ultrafast lattice heating on the 100 fs timescale. Such intrinsic attributes unequivocally designate Cu2FeS2 as an ideal thermoplasmonic material. It demonstrates superior photothermal conversion efficiencies (PCE) spanning both visible and NIR wavelengths, outperforming assorted well‐established photothermal materials including Au nanoparticles and MXene nanosheets. As a demonstration, we leverage its prominent thermoplasmonic functionality to drive efficient photothermal dry reforming of methane under low light intensities. Beyond the results presented here, Cu2FeS2 is expected to provide a fertile ground for transformative investigations in many diverse fields of science.

The last two decades have marked a revolution in materials science with the appearance of two novel groups of materials with promising features for future optoelectronics. The first are artificially fabricated metamaterials, composed of carefully engineered nanoparticle arrays, displaying tailored mie and plasmonic resonant responses [1]. The second are atomically thin two-dimensional (2D) semiconductor crystals, characterized by tightly bound excitons, promising for their flexible heterostructure stacking capabilities [2]. In this work we introduce a novel pulse-shaping approach, to study and control the coherent dynamics of resonant quasparticle excitations in such materials. By constructing a state-of-the-art pulse shaper for controlling the spectral phase of our sub-10 fs laser, we tailor the temporal order of instantaneous frequencies driving the noninstantaneous electronic response of the material on resonance [3]. We measure the response to various pulse shapes through monitoring the four-wave mixing (FWM) generation. Our contribution can be described by to three key aspects: We retrace the resonant dispersion by synchronizing the phase-dependent intra-pulse nonlinear wave-mixing with the prediction of the anharmonic oscillator model (AHO). We disentangle the multitude of interfering quantum pathways caused by the resonant dynamics, and reassemble them to achieve a strong nonlinear enhancement as well as near-complete destruction of the nonlinear yield. By controlling two successive resonant states, we present a glimpse into inter-state selectivity. We display nonlinear generation by improving the coherence in one state while suppressing the coherence in another. We believe this work places the control of coherent quasiparticle dynamics in condensed matter systems as a highly appealing field for both fundamental and applied research, such as improved nonlinear sensing, broadband compressed light sources and various ultrafast optoelectronic applications.

Hybrid metal-semiconductor nanostructures unifying plasmonic and high-refractive-index materials in a single resonant system demonstrate a wide set of unique optical properties. Such systems are a perspective for a broad palette of applications, but the link between their inner structure and optical properties is a very sensitive issue, which is still not revealed. Here, we describe the influence of internal microstructure of a hybrid gold-silicon nanoparticle (the gold nanoparticle with embedded silicon nanograins) on the up-conversion white-light photoluminescence. The evolution in the internal microstructure of the system during thermal treatment up to 500 °C is tracked in situ through the HAADF and EDS STEM techniques. The studies show the redistribution of the materials inside the hybrid nanoparticle and the reduction of the silicon nanograin numbers under heating without an external modification of the nanoparticle shape. We have established numerically that the dependence of the enhancement factor spectral width on the S/V ratio of the nanoparticle plasmonic component is close to the linear behavior. The shrinkage of the photoluminescence spectrum (up to 42%) of the hybrid nanoparticle reconfigured by laser exposure and thermal treatment is shown experimentally, which supports our numerical conclusions. The results shed light on the connection of optical properties of complex hybrid systems with their complex internal composition, providing a powerful tool to control their optical properties through microstructure rearrangement. They also open the way to the development of reconfigurable silicon-based up-conversion light nanosources for integrated optical devices and biophotonics.

This article reviews thermal properties of semiconductor and emergent plasmonic nanomaterials, focusing on mechanisms through which hot carriers and phonons are produced and dissipated as well as the related impacts on optoelectronic properties. Elevated equilibrium temperatures, of particular relevance for implementation of nanomaterials in devices, affect absorptive and radiative transitions as well as emission efficiency that can present reversible and irreversible changes with temperature. In noble metal or doped semiconductor/insulator nanomaterials, hot carriers and lattice heating can substantially influence localized surface plasmon resonances and yield large ultrafast changes in transmission or strongly oscillatory coherences. Transient optical and diffraction characterizations enable nonequilibrium investigations of phonon dynamics and cooling such as lattice expansion and crystal phase stability. Timescales of nanoparticle thermalization with surroundings and transport of heat within films of such materials are also discussed.

Plasmonic photocatalysts have demonstrated promising potential for enhancing the selectivity and efficiency of important chemical transformations. However, the relative contributions of nonphotothermal (i.e., hot carrier) and photothermal pathways remain a question of intense current debate, and the time scale and extent of surface adsorbate temperature change are still poorly understood. Using p-type Cu2-xSe nanocrystals as a semiconductor plasmonic platform and adsorbed Rhodamine B as a surface thermometer and hot carrier acceptor, we measure directly by transient absorption spectroscopy that the adsorbate temperature rises and decays with time constants of 1.4 ± 0.4 and 471 ± 126 ps, respectively, after the excitation of Cu2-xSe plasmon band at 800 nm. These time constants are similar to those for Cu2-xSe lattice temperature, suggesting that fast thermal equilibrium between the adsorbates and nanocrystal lattice is the main adsorbate heating pathway. This finding provides insights into the transient heating effect on surface adsorbates and their roles in plasmonic photocatalysis.

Optical properties of nanoparticle assemblies reflect distinctive characteristics of their building blocks and spatial organization, giving rise to emergent phenomena. Integrated experimental and computational studies have established design principles connecting the structure to properties for assembled clusters and superlattices. However, conventional electromagnetic simulations are too computationally expensive to treat more complex assemblies. Here we establish a fast, materials agnostic method to simulate the optical response of large nanoparticle assemblies incorporating both structural and compositional complexity. This many-bodied, mutual polarization method resolves limitations of established approaches, achieving rapid, accurate convergence for configurations including thousands of nanoparticles, with some overlapping. We demonstrate these capabilities by reproducing experimental trends and uncovering far- and near-field mechanisms governing the optical response of plasmonic semiconductor nanocrystal assemblies including structurally complex gel networks and compositionally complex mixed binary superlattices. This broadly applicable framework will facilitate the design of complex, hierarchically structured, and dynamic assemblies for desired optical characteristics.

No abstract available

No abstract available

No abstract available

The photothermally induced nanoscale dynamics of rapid melting and resolidification of a thin layer of molecular material surrounding a nanoparticle is examined in real time by an all-optical approach. The method employs pulsed periodic modulation of the medium's dielectric constant through absorption of a low-duty-cycle laser pulse train by a single nanoparticle that acts as a localized heating source. Interpretation of experimental data, including inference of a phase change and of the liquid/solid interface dynamics, is obtained by comparing experimental data with results from coupled optical-thermal numerical simulations. The combined experimental/computational workflow presented in this proof-of-principle study will enable future explorations of material parameters at nanoscale, which are often different from their bulk values and in many cases difficult to infer from macroscopic measurements.

Precise control and measurement of nanoparticles using low-power optical tweezers are pivotal for advancing single-particle analysis, nanoscale sensing, and energy transport research. In this work, we present the tip-assisted nanoparticle capture system that simultaneously achieves localized temperature probing and nanoparticle trapping, significantly lowering the required laser power input. Unlike traditional metal-tip plasmonic techniques that predominantly rely on intense electric field gradients, our approach employs a silicon nanotip under resonant laser excitation, uniquely integrating optical forces, thermophoretic forces, and interatomic interactions for stable nanoparticle confinement. This synergistic collaboration mechanism enables approximately a 42% reduction in laser power density compared to conventional bowtie nanoaperture methods. This experimental method achieved direct and simultaneous Raman-based measurements of localized thermal dynamics, providing new insights into nanoscale thermodynamics during optical trapping. Additionally, the silicon nanotip demonstrates reduced thermal transport due to its confined nanoscale geometry, aligning closely with our theoretical predictions. Our integrated strategy of efficient nanoparticle manipulation coupled with precise thermal probing not only enhances overall energy efficiency but also broadens the scope of potential applications in cutting-edge nanoscience and nanotechnology.

Metallic inks with superior conductivity and printability are necessary for high-throughput manufacturing of printed electronics. In particular, gallium-based liquid metal inks have shown great potential in creating soft, flexible and stretchable electronics. Despite their metallic composition, as-printed liquid metal nanoparticle films are non-conductive due to the surrounding metal oxide shells which are primarily Ga2O3, a wide-bandgap semiconductor. Hence, these films require a sintering process to recover their conductivity. For conventional solid metallic nanoparticles, thermal and laser processing are two commonly used sintering methods, and the sintering mechanism is well understood. Nevertheless, laser sintering of liquid metal nanoparticles was only recently demonstrated, and to date, the effect of thermal sintering has rarely been investigated. Here, eutectic gallium-indium nanoparticle films are processed separately by laser or thermal sintering in an ambient environment. Laser and thermally sintered films are compared with respect to electrical conductivity, surface morphology and elemental composition, crystallinity and surface composition. Both methods impart thermal energy to the films and generate thermal stress in the particles, resulting in rupture of the gallium oxide shells and achieving electrical conductivity across the film. For laser sintering, extensive oxide rupture allows liquid metal cores to flow out and coalesce into conductive pathways. For thermal sintering, due to less thermal stress and more oxidation, the oxide shells only rupture locally and extensive phase segregation occurs, leading to non-liquid particle films at room temperature. Electrical conductivity is instead attributed to segregated metal layers and gallium oxide which becomes crystalline and conductive at high temperatures. This comprehensive comparison confirms the necessity of oxidation suppression and significant thermal stress via instantaneous laser irradiation to achieve conductive patterns in liquid form.

The electronic structure of the gold nanoparticle–titanium dioxide (AuNP–TiO2) heterojunction plays a critical role for charge transfer and recombination dynamics that underpin its photocatalytic function. However, building a representative model to capture the key physics remains a significant challenge. Here, we investigate the influence of the AuNP size and shape, as well as oxygen vacancy (VO) defects at the anatase-phase TiO2 (101) surface and the temperature of the heterojunction, on its interfacial electronic properties. Using density functional theory (DFT), we compare the closed-shell Au20 and open-shell Au19 clusters interfaced with pristine and VO defect TiO2 surfaces. We find that the presence of a VO defect transforms pure TiO2 from a p-type to an n-type semiconductor, reversing the interfacial band bending from downward to upward. For the heterosystem, density of states (DOS) analysis shows that VO minimally affects the open-shell Au19–TiO2 system, but it significantly alters the closed-shell Au20–TiO2 system, converting it from p-type to n-type at the Γ-point at 0 K. Furthermore, ab initio molecular dynamics (AIMD) simulations at 300 K reveal significant thermal fluctuations in AuNP positions relative to the TiO2 surface. These fluctuations result in dynamic variations in the gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) in all systems studied: Au19NP–Pristine TiO2, Au20NP–Pristine TiO2, Au19NP–VO defect TiO2, and Au20NP–VO defect TiO2. Complementary Bader charge analysis performed at both 0 K and finite-temperature AIMD snapshots supports the emergence of an upward band bending and the formation of a Schottky barrier at the VO containing heterojunctions. Notably, we find that at finite temperature, an Au atom can dynamically passivate the VO, leading to a pronounced widening of the HOMO–LUMO gap in the AuNP–VO defect TiO2 heterojunctions. Our computational findings underscore the pivotal role of the VO defect and thermal effects in modulating interfacial band alignment, electronic states, and HOMO–LUMO gaps, providing insights for designing Au–TiO2 heterojunctions with tailored electronic properties.

No abstract available

We investigated the carrier dynamics of ammonothermal Mn-compensated gallium nitride (GaN:Mn) semiconductors by using sub-bandgap and above-bandgap photo-excitation in a photoluminescence analysis and pump–probe measurements. The contactless probing methods elucidated their versatility for the complex analysis of defects in GaN:Mn crystals. The impurities of Mn were found to show photoconductivity and absorption bands starting at the 700 nm wavelength threshold and a broad peak located at 800 nm. Here, we determined the impact of Mn-induced states and Mg acceptors on the relaxation rates of charge carriers in GaN:Mn based on a photoluminescence analysis and pump–probe measurements. The electrons in the conduction band tails were found to be responsible for both the photoconductivity and yellow luminescence decays. The slower red luminescence and pump–probe decays were dominated by Mg acceptors. After photo-excitation, the electrons and holes were quickly thermalized to the conduction band tails and Mg acceptors, respectively. The yellow photoluminescence decays exhibited a 1 ns decay time at low laser excitations, whereas, at the highest ones, it increased up to 7 ns due to the saturation of the nonradiative defects, resembling the photoconductivity lifetime dependence. The fast photo-carrier decay time observed in ammonothermal GaN:Mn is of critical importance in high-frequency and high-voltage device applications.

No abstract available

No abstract available

Selective laser sintering of micro and nanoparticles has become a prominent additive manufacturing technology for making engineered components and conformal circuits. The sintering and melting behaviors of polymer, metal, and ceramic powders in this context have been thoroughly studied. Compared to metals or insulating ceramics, semiconductor grains present more complexity due to grain coarsening, elemental diffusion, and seepage effects under photovoltaic and photothermal influences. These factors offer a broad spectrum of opportunities for property modification. Nevertheless, there is an existing research gap in the area of laser sintering of semiconductor nanoparticles. In this research, In2O3 thin films were produced using varying sintering and melting regimes by adjusting the laser energy density and preheating temperature. The findings revealed that the In2O3, when in the melting regime, demonstrated significantly low carrier concentration and high carrier mobility due to adequate grain coarsening and weakened grain boundaries. Utilizing this unique melting regime, In2O3 homo-thermocouples with high Seebeck coefficients, reaching $\mathbf{133.7} \boldsymbol{\mu} \mathbf{V}/\mathbf{K}$, were developed. This was achieved by managing the extent of sintering/melting of the branched paths instead of altering the materials.

New research has discovered discrepancies in the melting points, plasma generation, and resulting changes in optoelectronic properties of semiconductor materials A2B6 and A3B5 when exposed to laser light, even when the experimental conditions are the same. Therefore, accurately determining the thresholds at which these complex semiconductor compounds melt and create plasma remains an unsolved task. This work utilizes nanosecond ruby laser irradiation to thoroughly examine fundamental characteristics of semiconductor compounds A2B6 and A3B5 when exposed to laser irradiation. This includes investigating the thresholds at which melting occurs, the production of plasma, and any changes in optoelectronic capabilities. The experimental results demonstrate notable discrepancies in the melting points and optoelectronic characteristics of various semiconductor materials when subjected to the same experimental conditions. The variations mostly arise from inherent statistical biases in the parameters of the sample. By employing photoacoustic and photoconductive techniques, we accurately ascertained the melting points of cadmium telluride, gallium arsenide, and aluminum gallium arsenide crystals, providing exact empirical data on the characteristics of these corresponding substances. In addition, we performed photoconductive spectroscopy tests on cadmium telluride exposed to nanosecond ruby laser pulses. We noticed a significant impact of the creation of a tellurium layer on the photoconductivity. The investigations showed that the existence of a tellurium layer results in photoconductivity that varies depending on the spectrum, with the most significant improvement observed in the short-wavelength region.

No abstract available

Ultraviolet nanosecond laser annealing (UV‐NLA) proves to be an important technique, particularly when tightly controlled heating and melting are necessary. In the realm of semiconductor technologies, the significance of NLA grows in tandem with the escalating intricacy of integration schemes in nanoscaled devices. Silicon–germanium alloys are studied for decades for their compatibility with silicon devices. Indeed, they enable the manipulation of properties like strain, carrier mobilities, and bandgap. In this framework, they can for instance boost the performances of p‐type MOSFETs but also enable near infrared absorption and emission for applications in photodetection and photonics. Laser melting on such types of layers, however, results, up to now, in the development of extended defects and poor control over layer morphology and homogeneity. Herein, the laser melting of ≈700 nm‐thick relaxed silicon–germanium samples coated with SiO2 nanoarrays, observing the resulting material to maintain an unaltered lattice, is investigated. It is found that the geometrical parameters of the silicon oxide have an impact on the thermal budget samples, influencing melt threshold, melt depth, and germanium distribution.

High-index dielectric and semiconductor nanoparticles supporting strong electric and magnetic resonances have drawn significant attention in recent years. However, until now, there have been no experimental reports of lasing action from such nanostructures. Here, we demonstrate directional lasing, with a low threshold and high quality factor, in active dielectric nanoantenna arrays achieved through a leaky resonance excited in coupled gallium arsenide (GaAs) nanopillars. The leaky resonance is formed by partially breaking a bound state in the continuum generated by the collective, vertical electric dipole resonances excited in the nanopillars for subdiffractive arrays. We control the directionality of the emitted light while maintaining a high quality factor (Q = 2,750). The lasing directivity and wavelength can be tuned via the nanoantenna array geometry and by modifying the gain spectrum of GaAs with temperature. The obtained results provide guidelines for achieving surface-emitting laser devices based on active dielectric nanoantennas that are compact and highly transparent.Active dielectric nanoantenna arrays exhibit low-threshold and high-quality-factor directional lasing achieved via a leaky resonance excited in coupled gallium arsenide (GaAs) nanopillars.

The acquisition of reliable knowledge about the mechanism of short laser pulse interactions with semiconductor materials is an important step for high-tech technologies towards the development of new electronic devices, the functionalization of material surfaces with predesigned optical properties, and the manufacturing of nanorobots (such as nanoparticles) for bio-medical applications. The laser-induced nanostructuring of semiconductors, however, is a complex phenomenon with several interplaying processes occurring on a wide spatial and temporal scale. In this work, we apply the atomistic–continuum approach for modeling the interaction of an fs-laser pulse with a semiconductor target, using monolithic crystalline silicon (c-Si) and porous silicon (Si). This model addresses the kinetics of non-equilibrium laser-induced phase transitions with atomic resolution via molecular dynamics, whereas the effect of the laser-generated free carriers (electron–hole pairs) is accounted for via the dynamics of their density and temperature. The combined model was applied to study the microscopic mechanism of phase transitions during the laser-induced melting and ablation of monolithic crystalline (c-Si) and porous Si targets in a vacuum. The melting thresholds for the monolithic and porous targets were found to be 0.32 J/cm2 and 0.29 J/cm2, respectively. The limited heat conduction mechanism and the absence of internal stress accumulation were found to be involved in the processes responsible for the lowering of the melting threshold in the porous target. The results of this modeling were validated by comparing the melting thresholds obtained in the simulations to the experimental values. A difference in the mechanisms of ablation of the c-Si and porous Si targets was considered. Based on the simulation results, a prediction regarding the mechanism of the laser-assisted production of Si nanoparticles with the desired properties is drawn.

Highly active, structurally disordered CoFe2O4/CoO electrocatalysts are synthesized by pulsed laser fragmentation in liquid (PLFL) of a commercial CoFe2O4 powder dispersed in water. A partial transformation of the CoFe2O4 educt to CoO is observed and proposed to be a thermal decomposition process induced by the picosecond pulsed laser irradiation. The overpotential in the OER in aqueous alkaline media at 10 mA cm−2 is reduced by 23% compared to the educt down to 0.32 V with a Tafel slope of 71 mV dec−1. Importantly, the catalytic activity is systematically adjustable by the number of PLFL treatment cycles. The occurrence of thermal melting and decomposition during one PLFL cycle is verified by modelling the laser beam energy distribution within the irradiated colloid volume and comparing the by single particles absorbed part to threshold energies. Thermal decomposition leads to a massive reduction in particle size and crystal transformations towards crystalline CoO and amorphous CoFe2O4. Subsequently, thermal melting forms multi-phase spherical and network-like particles. Additionally, Fe-based layered double hydroxides at higher process cycle repetitions emerge as a byproduct. The results show that PLFL is a promising method that allows modification of the structural order in oxides and thus access to catalytically interesting materials.

Herein, we combine titania layers with gold species in a laser-supported process and report a substantial change of properties of the resulting heterostructures depending on the major processing parameters. Electrodes were fabricated via an anodisation process complemented with calcination to ensure a crystalline phase, and followed by magnetron sputtering of metallic films. The obtained TiO2 nanotubes with deposited thin (5, 10 nm) Au films were treated with a UV laser (355 nm) to form Au nanoparticles on top of the nanotubes. It was proven that selected laser working parameters ensure not only the formation of Au nanoparticles, but also simultaneously provide preservation of the initial tubular architecture, while above-threshold laser fluences result in partial destruction (melting) of the top layer of the nanotubes. For almost all of the samples, the crystalline phase of the nanotubes observed in Raman spectra was maintained independently of the laser processing parameters. Enhanced photoresponse up to ca 6 mA/cm2 was demonstrated by photoelectrochemical measurements on samples obtained by laser annealing of the 10 nm Au coating on a titania support. Moreover, a Mott–Schottky analysis indicated the dramatically increased (two orders of magnitude) concentration of donor density in the case of a laser-treated Au–TiO2 heterojunction compared to reference electrodes.

Non-vacuum printing of single crystals would be ideal for high performance functional devices (such as electronics) fabrication, yet challenging for most materials, especially, for inorganic semiconductors. Currently, the printed films are dominantly in amorphous, polycrystalline or nanoparticle films. In this article, manufacturing of single-crystal silicon micro/nano island is attempted. Different from traditional vapor deposition for silicon thin film preparation, silicon nanoparticle ink was aerosol printed followed by confined laser melting and crystallization allowing potential fabrication of single-crystal silicon micro/nano islands. It is also shown as-fabricated Si islands can be transfer printed onto polymer substrates for potential application of flexible electronics. The additive nature of this technique suggests a scalable and economical approach for high crystallinity semiconductor printing.

Supported particles are easily accessible as standard materials used in heterogeneous catalysis and photocatalysis. This article addresses our exemplary studies on the integration of supported nanoparticles into their solid support, namely gold nanoparticles into zinc oxide sub-micrometer spheres, by energy controlled pulsed laser melting in a free liquid jet. This one-step, continuous flow-through processing route reverses the educt's structure, converting the ligand-free surface adsorbate into a spherical subsurface solid inclusion within its former support. The results show how a nanoparticulate surface adsorbate can be included in the form of crystalline nanoparticles into the resolidified support matrix, demonstrated by using plasmonic nanoparticles and semiconductor microparticles as reference materials.

No abstract available

Although multiphoton-pumped lasing from a solution of chromophores is important in the emerging fields of nonlinear optofluidics and bio-photonics, conventionally used organic dyes are often rendered unsuitable because of relatively small multiphoton absorption cross-sections and low photostability. Here, we demonstrate highly photostable, ultralow-threshold multiphoton-pumped biexcitonic lasing from a solution of colloidal CdSe/CdS nanoplatelets within a cuvette-based Fabry–Pérot optical resonator. We find that colloidal nanoplatelets surprisingly exhibit an optimal lateral size that minimizes lasing threshold. These nanoplatelets possess very large gain cross-sections of 7.3 × 10−14 cm2 and ultralow lasing thresholds of 1.2 and 4.3 mJ cm−2 under two-photon (λexc=800 nm) and three-photon (λexc=1.3 μm) excitation, respectively. The highly polarized emission from the nanoplatelet laser shows no significant photodegradation over 107 laser shots. These findings constitute a more comprehensive understanding of the utility of colloidal semiconductor nanoparticles as the gain medium in high-performance frequency-upconversion liquid lasers. Multiphoton-pumped lasing from semiconductor nanocrystals in solution is difficult due to Auger recombination, low volume fraction and high threshold. Here, Li et al. demonstrate photostable, ultralow threshold multi-photon pumped lasing from colloidal CdSe/CdS nanoplatelets in a Fabry-Pérot optical resonator.

No abstract available

No abstract available

No abstract available

The study of the process of laser action on powder materials requires the construction of mathematical models of the interaction of laser radiation with powder particles that take into account the features of energy supply and are applicable in a wide range of beam parameters and properties of the particle material. A model of the interaction of pulsed or pulse-periodic laser radiation with a spherical metal particle is developed. To find the temperature distribution in the particle volume, the non-stationary three-dimensional heat conductivity equation with a source term that takes into account the action of laser radiation is solved. In the plane normal to the direction of propagation of laser radiation, the change in the radiation intensity obeys the Gaussian law. It is possible to take into account changes in the intensity of laser radiation in space due to its absorption by the environment. To accelerate numerical calculations, a computational algorithm is used based on the use of vectorized data structures and parallel implementation of operations on general-purpose graphics accelerators. The features of the software implementation of the method for solving a system of difference equations that arises as a result of finite-volume discretization of the heat conductivity equation with implicit scheme by the iterative method are presented. The model developed describes the heating and melting of a spherical metal particle exposed by multi-pulsed laser radiation. The implementation of the computational algorithm developed is based on the use of vectorized data structures and GPU resources. The model and calculation results are of interest for constructing a two-phase flow model describing the interaction of test particles with laser radiation on the scale of the entire calculation domain. Such a model is implemented using a discrete-trajectory approach to modeling the motion and heat exchange of a dispersed admixture.

No abstract available

Electron and lattice heat transport have been investigated in bilayer thin films of gold and CoSb3  after photo-excitation of the nanometric top gold layer through picosecond x-ray scattering in a pump-probe setup. The kinetics of heat transfer are detected by thermal lattice expansion and compared to simulations based on the two-temperature model of coupling of electron and phonon degrees of freedom. The unexpected observation of a larger portion of the deposited heat being detected in the underlying CoSb3  layer before the topmost gold layer is heated supports the picture of transport of the photo-excited electrons from gold to the underlying layer to be converted into lattice heat. The change of partition of heat between the gold and CoSb3  layer with laser fluence and wavelength (either exciting intraband transitions or additionally interband transitions) is rooted in the amplitude of electron temperature. Higher electron temperatures result in a longer equilibration time with the lattice and thus a larger proportion of ballistic electron transport across the interface.

No abstract available

The dewetting conditions of ultrathin Ag films under pulsed laser annealing were investigated. Ag films with a nominal average thickness of 9 nm were deposited on fused silica substrates by DC magnetron sputtering and annealed using a KrF excimer laser (λ = 248 nm and pulse width = 5 ns). The annealing process was monitored in situ via spectrophotometric transmittance measurements over a wavelength range of 230–1000 nm, while the resulting microstructural changes were characterized by atomic force microscopy and scanning electron microscopy imaging. Depending on the laser energy density, the films underwent transitions from smooth surfaces to bi-continuous layers and eventually to well-separated nanoparticles. Experimental results were compared with numerical simulations based on a 1D heat transfer model, simulating the evolution of the film's temperature during each laser pulse. The theoretical minimum laser energy density (40–43 mJ/cm2 at room temperature) required to initiate dewetting aligned closely with experimental observations. This study highlights the influence of initial film temperature, demonstrating that higher temperatures lower the energy density threshold for dewetting and vice versa.

Modeling elementary diffusion processes in nanostructured materials is essential for developing platforms capable of interacting with high-speed physical signals. In this work, the photothermal response of a nano-hydroxyapatite/carbon nanotube (nHAp/CNT) composite was experimentally characterized and modeled through a cellular automaton (CA) framework designed to capture the thermal propagation of the hybrid system. Synthesizing nHAp/CNT composites enables the combination of the biocompatible and piezoelectric nature of nHAp with the enhanced photothermal response introduced by CNTs. UV–Vis reflectance measurements confirmed that CNT incorporation increases the optical absorption of the ceramic matrix, resulting in more efficient photothermal conversion. The composite was irradiated with a nanosecond pulsed laser, and the resulting thermal transients were compared with CA simulations based on a D2Q9 lattice configuration. The model accurately reproduces experiments, achieving R2 > 0.991 and NRMSE below 2.4% for all tested laser powers. This strong correspondence validates the CA approach for predicting spatiotemporal heat diffusion in heterogeneous nanostructured composites. Furthermore, the model revealed a sensitive thermal coupling when two heat sources were considered, indicating synergistic enhancement of local temperature fields. These findings demonstrate both the effective integration of CNTs within the nHAp matrix and the capability of CA-based modeling to describe their photothermal behavior. Overall, this study establishes a computational–experimental basis for designing controlled thermal-wave propagation and guiding future multi-frequency or multi-source photothermal mixing experiments.

This study presents a comprehensive numerical investigation of the photothermal response of core-shell gold nanoshell (CGNS) and gold nanorod (CGNR) under femtosecond (fs) laser pulse irradiation. Using the two-temperature model (TTM) integrated with finite element modeling in COMSOL Multiphysics, we simulated the optical and thermal dynamics of these nanostructures. A key innovation in our approach is incorporating the temperature dependencies of electron heat capacity and electron-phonon coupling, allowing us to capture the non-linear thermal response at elevated electron temperatures. Our analysis showed that, while lattice temperatures increased linearly with laser fluence, electron temperatures exhibited a more complex non-linear trend, emphasizing the need for advanced modeling in high-fluence regimes. We evaluated how variations in key parameters, including aspect ratio, shell thickness, pulse duration, and refractive index, influence the optical and thermal properties of the nanostructures. Results revealed that CGNRs with higher aspect ratios exhibited significant red-shifts into the near-infrared (NIR) region, making them ideal for deep-tissue imaging and photothermal therapy (PTT), while thicker CGNS nanostructures demonstrated blue-shifts with reduced energy absorption. Shorter pulse durations led to higher peak electron temperatures, with CGNRs displaying faster heat dissipation than CGNS due to their elongated geometry. Furthermore, CGNRs demonstrated enhanced sensitivity to changes in the refractive index of the surrounding medium, making them particularly suited for sensing applications in the NIR-II region. This study provides key insights into optimizing core-shell nanostructures for advanced PTT and sensing technologies, laying the groundwork for the development of tailored nanomaterials for biomedical applications.

Janus nanoparticles (JNPs) with heterogeneous compositions or interfacial properties can exhibit directional heating upon external excitation with optical or magnetic energy. This directional heating may be harnessed for new nanotechnology and biomedical applications. However, it remains unclear how the JNP properties (size, interface) and laser excitation method (pulsed vs. continuous) regulate the directional heating. Here, we developed a numerical framework to analyze the asymmetric thermal transport in JNP heating under photothermal stimulation. We found that JNP-induced temperature contrast, defined as the ratio of temperature increase on the opposite sides in the surrounding medium, is highest for smaller JNPs and when a low thermal resistance coating covers a minor fraction of JNP surface. Notably, we discovered up to 20-fold enhancement of the temperature contrast based on thermal confinement under pulsed heating compared with continuous heating. This work brings new insights to maximize the asymmetric thermal responses for JNP heating.