В работе представлены результаты экспериментальных исследований процессов формирования фотоакусти... more В работе представлены результаты экспериментальных исследований процессов формирования фотоакустического отклика в наноструктурированных композитных системах «пористая матрица - жидкость». Рассмотрены случаи низкочастотной периодической модуляции и импульсного лазерного возбуждения. Уставлено, что в обоих случаях амплитуда фотоакустического отклика существенно возрастает с ростом пористости матрицы. Предложена упрощенная модель композитной системы на основе пористой матрицы, что позволило выполнить корректные (согласуются с экспериментом) оценки величин модулей Юнга и коэффициентов теплового расширения композитных систем разной пористости, а также величин амплитуды акустических откликов.В роботі представлено результати експериментальних досліджень процесів формування фотоакустичного відгуку в наноструктурованих композитних системах «порувата матриця - рідина». Розглянуто випадки низькочастотної періодичної модуляції та імпульсного лазерного збудження. Встановлено, що в обох випадках амплітуда фотоакустичного відгуку істотно зростає з ростом поруватості матриці. Запропоновано спрощену модель композитної системи на основі поруватої матриці, що дозволило виконати коректні (узгоджуються з експериментом) оцінки величин модулів Юнга і коефіцієнтів теплового розширення композитних систем різної поруватості, а також величин амплітуди акустичних відгуків.The results of experimental studies of the processes of photoacoustic response formation in nanostructured composite systems «porous matrix-liquid» are presented. The cases of low-frequency periodic modulation and pulsed laser excitation are considered. It is established that in both cases the amplitude of the photoacoustic response increases substantially with the matrix porosity increase. A simplified model of a composite system based on a porous matrix was proposed, which allowed to carry out correct estimates of the Young's modulus and the thermal expansion coefficients of composite systems with different porosity, as well as the amplitude of the acoustic response (in agreement with experiment)
In this work photoacoustic conversion efficiency was analyzed in the porous silicon (PSi) and in ... more In this work photoacoustic conversion efficiency was analyzed in the porous silicon (PSi) and in the composite based on it, such as the "porous matrix-liquid" was analyzed. The minimum of phase on frequency dependence was observed experimentally and theoretically. This minimum is caused by summation of the different species of PA signal-thermal piston and termoelastic bending (drum effect). Experiments showed that the effective dynamic (rapid changes on temperature) coefficient of the thermal expansion of the "PSiliquid" composite exceeds the thermal expansion coefficient of the porous silicon more than in 40 times as proved by experiments conducted.
Combined photothermoacoustic and photoelectric microscopy is used to investigate silicon-based st... more Combined photothermoacoustic and photoelectric microscopy is used to investigate silicon-based structures: an epitaxially grown n-type region in a p-type substrate, a p-p + interface obtained by implanting boron ions, and a region near a crack tip. It is concluded that the visualization of epitaxial regions by thermal waves most probably stems from the elastic stresses appearing during fabrication of the structures. It is shown that the spatial distribution of the elastic stresses appearing upon ion implantation is visualized by thermal waves. In the region near the crack tip inhomogeneities in the thermoelastic and energy properties extending over hundreds of microns can be diagnosed by thermal waves and electron-hole plasma waves. Spatial periodicity with a period ∼85 m is discovered in the variation of the thermoelastic properties near the crack tip.
Metal-induced crystallization in Si-Sn-Si thin film structures has been studied, by using the Ram... more Metal-induced crystallization in Si-Sn-Si thin film structures has been studied, by using the Raman scattering at various light powers. The Raman spectra are used to monitor the temperature, size, and concentration of Si crystals formed in the amorphous Si matrix. A significant acceleration of the metal-induced crystallization in Si-Sn-Si structures at their laser-assisted annealing in comparison with their annealing in dark is revealed. A basic possibility of the "on line" monitoring of the size and the concentration of Si nanocrystals in the course of their formation is demonstrated. K e y w o r d s: solar cell, thin films, nanocrystals, silicon, tin, metal-induced crystallization.
In the paper the experimental study of heat transport across the interface "porous silicon/liquid... more In the paper the experimental study of heat transport across the interface "porous silicon/liquid" by photoacoustic technique is reported. Two cases with and without liquid covering of porous silicon surface were considered. Thermal perturbations were excited at the surface of porous silicon as a result of absorption of the light with modulated intensity. The resulting thermal-elastic stresses arising in the system were registered with piezoelectric transducer. The amplitude-frequency dependencies of the voltage on the piezoelectric electrodes were measured. The presence of the liquid film leads to decreasing of the amplitude of photoacoustic signal as a result of the thermal energy evacuation from the porous silicon into the liquid. The experimental dependencies were fitted with the results of simulation that takes into account heat fluxes separation at the porous silicon/liquid interface. With the presented method one can precisely measure heat fluxes transferred from the solid into contacting fluid. Moreover, the presented approach can be easily adopted for the thermal conductivity study of the different nanofluids as well as thermal resistance at the interface nanostructured solid/fluid.
This work describes tin-induced crystallization of amorphous silicon studied with Raman spectrosc... more This work describes tin-induced crystallization of amorphous silicon studied with Raman spectroscopy in thin-film structures Si-Sn-Si irradiated with pulsed laser light. We have found and analyzed dependencies of the nanocrystals' size and concentration on the laser pulse intensity for 10 ns and 150 𝜇m duration laser pulses at the wavelengths of 535 nm and 1070 nm. Efficient transformation of the amorphous silicon into a crystalline phase during the 10 ns time interval of the acting laser pulse in the 200 nm thickness films of the amorphous silicon was demonstrated. The results were analyzed theoretically by modeling the spatial and temporal distribution of temperature in the amorphous silicon sample within the laser spot location. Simulations confirmed importance of light absorption depth (irradiation wavelength) in formation and evolution of the temperature profile that affects the crystallization processes in irradiated structures.
International Journal of Thermal Sciences, Dec 1, 2018
Features of thermal transport in multilayered porous silicon nanostructures are considered. Such ... more Features of thermal transport in multilayered porous silicon nanostructures are considered. Such nanostructures were fabricated by electrochemical etching of monocrystalline Si substrates by applying periodically changed current density. Hereby, the multilayered structures with specific phononic properties were formed. Photoacoustic (PA) technique in gas-microphone configuration was applied for
ABSTRACT The aim of the paper is to present the results of a laser photoacoustic microscopy study... more ABSTRACT The aim of the paper is to present the results of a laser photoacoustic microscopy study applied to subsurface damage visualization and inhomogeneity detection in semiconductor and ceramic materials. For comparison photoelectric microscopy was used
An efficient technique for low temperature metal-induced nanocrystalline silicon fabrication is p... more An efficient technique for low temperature metal-induced nanocrystalline silicon fabrication is presented. The technique is based on laser annealing of thin films of "amorphous silicon-tin" composites combined with in situ control and monitoring with Raman technique. Laser annealing was shown to provide the possibility of fine-tuning the nanocrystals size and concentration, which is important in photovoltaic and thermoelectric devices fabrication.
Abstract Generation processes of a photoacoustic response of a layered polyethylene/hydrogel stru... more Abstract Generation processes of a photoacoustic response of a layered polyethylene/hydrogel structure by its irradiation with periodically modulated light have been experimentally studied. The heat sources are located in a gel near the interface with polyethylene. The response in the form of the pressure oscillations occurs as a result of the thermoelastic strain of the polyethylene layer by its thickness-nonuniform heating by a thermal wave. The obtained results can be useful for modification of the techniques based on the diffusion processes in gels.
The paper is devoted to the study of the features of CdTe surface treatment under laser irradiati... more The paper is devoted to the study of the features of CdTe surface treatment under laser irradiation with both different wavelengths (λ = 300–800 nm) and pulse durations (τp = 7 ns–1 ms). The thermal conductivity of the semi-insulating p-like CdTe semiconductor crystals was evaluated using the photoacoustic gas-microphone method. Simulations of the melting threshold were performed based on the three stage model of the laser induced excitation and relaxation. In particular, the following processes were considered in frames of the model: (i) rapid interband thermalization, (ii) nonradiative interband and (iii) nonradiative surface recombination. It was revealed that in the range of pulse durations from 7 ns to 1 μs, the melting threshold of the CdTe mainly depended on the absorption coefficient α(λ). For pulse durations longer than 1 μs the threshold started to depend also on the spectra of the reflectivity coefficient R(λ). The obtained results have been used for optimization of the laser-assisted techniques of surface processing and stimulated doping of CdTe crystals.
Laser ultrasound enhancement with carbon-based nanomaterials incorporated into phantom tissues is... more Laser ultrasound enhancement with carbon-based nanomaterials incorporated into phantom tissues is reported. More specifically, impact of nanodiamonds and graphene oxide on the efficiency of photoinduced pressure excitation was investigated. Agarose-based phantom tissues with and without the nanoparticles were compared. The second harmonic of pulsed Nd:Yag laser (532 nm) was chosen for ultrasound generation. Specific acoustic probe was fabricated for laser-induced ultrasound registration. Dependence of the ultrasound amplitude on concentration of the nanoparticles incorporated into the phantom tissues was analyzed in details. The most significant enhancement of the amplitude ensured by graphene oxide was stated. Considering biocompatibility of the both types of carbon-based nanomaterials, they can be potentially used in future as contrast agents for bio-imaging and theranostic applications.
THERMOPHYSICS 2019: 24th International Meeting of Thermophysics and 20th Conference REFRA, 2019
Features of heat transport in silicon-based porous structures with different morphology before an... more Features of heat transport in silicon-based porous structures with different morphology before and after thermal annealing are investigated. Specifically, fractal-like porous silicon and silicon nanowire arrays samples were considered. All the structures were annealed in dry air at various temperatures in diapason from 600 °C up to 1000 °C for 20 minutes. The photoacoustic technique with gas-microphone registration was applied for the thermal diffusivity evaluation of the samples. Particularly, the amplitude frequency dependencies of photoacoustic response from the considered samples in the classical gas-microphone configuration were measured in the range from 10 Hz to 3 kHz. The simulation of the experimental dependencies with the use of appropriate model allowed us to evaluate thermal conductivity. It was found that the short time thermal annealing together with increasing annealing temperature leads to significant reduction of thermal transport in mesoporous silicon. On the opposite, the thermal properties of silicon nanowires remain unaffected.
Features of thermal transport in multilayered porous silicon nanostructures are considered. Such ... more Features of thermal transport in multilayered porous silicon nanostructures are considered. Such nanostructures were fabricated by electrochemical etching of monocrystalline Si substrates by applying periodically changed current density. Hereby, the multilayered structures with specific phononic properties were formed. Photoacoustic (PA) technique in gas-microphone configuration was applied for
Combined photothermoacoustic and photoelectric microscopy is used to investigate silicon-based st... more Combined photothermoacoustic and photoelectric microscopy is used to investigate silicon-based structures: an epitaxially grown n-type region in a p-type substrate, a p-p + interface obtained by implanting boron ions, and a region near a crack tip. It is concluded that the visualization of epitaxial regions by thermal waves most probably stems from the elastic stresses appearing during fabrication of the structures. It is shown that the spatial distribution of the elastic stresses appearing upon ion implantation is visualized by thermal waves. In the region near the crack tip inhomogeneities in the thermoelastic and energy properties extending over hundreds of microns can be diagnosed by thermal waves and electron-hole plasma waves. Spatial periodicity with a period ∼85 m is discovered in the variation of the thermoelastic properties near the crack tip.
В работе представлены результаты экспериментальных исследований процессов формирования фотоакусти... more В работе представлены результаты экспериментальных исследований процессов формирования фотоакустического отклика в наноструктурированных композитных системах «пористая матрица - жидкость». Рассмотрены случаи низкочастотной периодической модуляции и импульсного лазерного возбуждения. Уставлено, что в обоих случаях амплитуда фотоакустического отклика существенно возрастает с ростом пористости матрицы. Предложена упрощенная модель композитной системы на основе пористой матрицы, что позволило выполнить корректные (согласуются с экспериментом) оценки величин модулей Юнга и коэффициентов теплового расширения композитных систем разной пористости, а также величин амплитуды акустических откликов.В роботі представлено результати експериментальних досліджень процесів формування фотоакустичного відгуку в наноструктурованих композитних системах «порувата матриця - рідина». Розглянуто випадки низькочастотної періодичної модуляції та імпульсного лазерного збудження. Встановлено, що в обох випадках амплітуда фотоакустичного відгуку істотно зростає з ростом поруватості матриці. Запропоновано спрощену модель композитної системи на основі поруватої матриці, що дозволило виконати коректні (узгоджуються з експериментом) оцінки величин модулів Юнга і коефіцієнтів теплового розширення композитних систем різної поруватості, а також величин амплітуди акустичних відгуків.The results of experimental studies of the processes of photoacoustic response formation in nanostructured composite systems «porous matrix-liquid» are presented. The cases of low-frequency periodic modulation and pulsed laser excitation are considered. It is established that in both cases the amplitude of the photoacoustic response increases substantially with the matrix porosity increase. A simplified model of a composite system based on a porous matrix was proposed, which allowed to carry out correct estimates of the Young's modulus and the thermal expansion coefficients of composite systems with different porosity, as well as the amplitude of the acoustic response (in agreement with experiment)
In this work photoacoustic conversion efficiency was analyzed in the porous silicon (PSi) and in ... more In this work photoacoustic conversion efficiency was analyzed in the porous silicon (PSi) and in the composite based on it, such as the "porous matrix-liquid" was analyzed. The minimum of phase on frequency dependence was observed experimentally and theoretically. This minimum is caused by summation of the different species of PA signal-thermal piston and termoelastic bending (drum effect). Experiments showed that the effective dynamic (rapid changes on temperature) coefficient of the thermal expansion of the "PSiliquid" composite exceeds the thermal expansion coefficient of the porous silicon more than in 40 times as proved by experiments conducted.
Combined photothermoacoustic and photoelectric microscopy is used to investigate silicon-based st... more Combined photothermoacoustic and photoelectric microscopy is used to investigate silicon-based structures: an epitaxially grown n-type region in a p-type substrate, a p-p + interface obtained by implanting boron ions, and a region near a crack tip. It is concluded that the visualization of epitaxial regions by thermal waves most probably stems from the elastic stresses appearing during fabrication of the structures. It is shown that the spatial distribution of the elastic stresses appearing upon ion implantation is visualized by thermal waves. In the region near the crack tip inhomogeneities in the thermoelastic and energy properties extending over hundreds of microns can be diagnosed by thermal waves and electron-hole plasma waves. Spatial periodicity with a period ∼85 m is discovered in the variation of the thermoelastic properties near the crack tip.
Metal-induced crystallization in Si-Sn-Si thin film structures has been studied, by using the Ram... more Metal-induced crystallization in Si-Sn-Si thin film structures has been studied, by using the Raman scattering at various light powers. The Raman spectra are used to monitor the temperature, size, and concentration of Si crystals formed in the amorphous Si matrix. A significant acceleration of the metal-induced crystallization in Si-Sn-Si structures at their laser-assisted annealing in comparison with their annealing in dark is revealed. A basic possibility of the "on line" monitoring of the size and the concentration of Si nanocrystals in the course of their formation is demonstrated. K e y w o r d s: solar cell, thin films, nanocrystals, silicon, tin, metal-induced crystallization.
In the paper the experimental study of heat transport across the interface "porous silicon/liquid... more In the paper the experimental study of heat transport across the interface "porous silicon/liquid" by photoacoustic technique is reported. Two cases with and without liquid covering of porous silicon surface were considered. Thermal perturbations were excited at the surface of porous silicon as a result of absorption of the light with modulated intensity. The resulting thermal-elastic stresses arising in the system were registered with piezoelectric transducer. The amplitude-frequency dependencies of the voltage on the piezoelectric electrodes were measured. The presence of the liquid film leads to decreasing of the amplitude of photoacoustic signal as a result of the thermal energy evacuation from the porous silicon into the liquid. The experimental dependencies were fitted with the results of simulation that takes into account heat fluxes separation at the porous silicon/liquid interface. With the presented method one can precisely measure heat fluxes transferred from the solid into contacting fluid. Moreover, the presented approach can be easily adopted for the thermal conductivity study of the different nanofluids as well as thermal resistance at the interface nanostructured solid/fluid.
This work describes tin-induced crystallization of amorphous silicon studied with Raman spectrosc... more This work describes tin-induced crystallization of amorphous silicon studied with Raman spectroscopy in thin-film structures Si-Sn-Si irradiated with pulsed laser light. We have found and analyzed dependencies of the nanocrystals' size and concentration on the laser pulse intensity for 10 ns and 150 𝜇m duration laser pulses at the wavelengths of 535 nm and 1070 nm. Efficient transformation of the amorphous silicon into a crystalline phase during the 10 ns time interval of the acting laser pulse in the 200 nm thickness films of the amorphous silicon was demonstrated. The results were analyzed theoretically by modeling the spatial and temporal distribution of temperature in the amorphous silicon sample within the laser spot location. Simulations confirmed importance of light absorption depth (irradiation wavelength) in formation and evolution of the temperature profile that affects the crystallization processes in irradiated structures.
International Journal of Thermal Sciences, Dec 1, 2018
Features of thermal transport in multilayered porous silicon nanostructures are considered. Such ... more Features of thermal transport in multilayered porous silicon nanostructures are considered. Such nanostructures were fabricated by electrochemical etching of monocrystalline Si substrates by applying periodically changed current density. Hereby, the multilayered structures with specific phononic properties were formed. Photoacoustic (PA) technique in gas-microphone configuration was applied for
ABSTRACT The aim of the paper is to present the results of a laser photoacoustic microscopy study... more ABSTRACT The aim of the paper is to present the results of a laser photoacoustic microscopy study applied to subsurface damage visualization and inhomogeneity detection in semiconductor and ceramic materials. For comparison photoelectric microscopy was used
An efficient technique for low temperature metal-induced nanocrystalline silicon fabrication is p... more An efficient technique for low temperature metal-induced nanocrystalline silicon fabrication is presented. The technique is based on laser annealing of thin films of "amorphous silicon-tin" composites combined with in situ control and monitoring with Raman technique. Laser annealing was shown to provide the possibility of fine-tuning the nanocrystals size and concentration, which is important in photovoltaic and thermoelectric devices fabrication.
Abstract Generation processes of a photoacoustic response of a layered polyethylene/hydrogel stru... more Abstract Generation processes of a photoacoustic response of a layered polyethylene/hydrogel structure by its irradiation with periodically modulated light have been experimentally studied. The heat sources are located in a gel near the interface with polyethylene. The response in the form of the pressure oscillations occurs as a result of the thermoelastic strain of the polyethylene layer by its thickness-nonuniform heating by a thermal wave. The obtained results can be useful for modification of the techniques based on the diffusion processes in gels.
The paper is devoted to the study of the features of CdTe surface treatment under laser irradiati... more The paper is devoted to the study of the features of CdTe surface treatment under laser irradiation with both different wavelengths (λ = 300–800 nm) and pulse durations (τp = 7 ns–1 ms). The thermal conductivity of the semi-insulating p-like CdTe semiconductor crystals was evaluated using the photoacoustic gas-microphone method. Simulations of the melting threshold were performed based on the three stage model of the laser induced excitation and relaxation. In particular, the following processes were considered in frames of the model: (i) rapid interband thermalization, (ii) nonradiative interband and (iii) nonradiative surface recombination. It was revealed that in the range of pulse durations from 7 ns to 1 μs, the melting threshold of the CdTe mainly depended on the absorption coefficient α(λ). For pulse durations longer than 1 μs the threshold started to depend also on the spectra of the reflectivity coefficient R(λ). The obtained results have been used for optimization of the laser-assisted techniques of surface processing and stimulated doping of CdTe crystals.
Laser ultrasound enhancement with carbon-based nanomaterials incorporated into phantom tissues is... more Laser ultrasound enhancement with carbon-based nanomaterials incorporated into phantom tissues is reported. More specifically, impact of nanodiamonds and graphene oxide on the efficiency of photoinduced pressure excitation was investigated. Agarose-based phantom tissues with and without the nanoparticles were compared. The second harmonic of pulsed Nd:Yag laser (532 nm) was chosen for ultrasound generation. Specific acoustic probe was fabricated for laser-induced ultrasound registration. Dependence of the ultrasound amplitude on concentration of the nanoparticles incorporated into the phantom tissues was analyzed in details. The most significant enhancement of the amplitude ensured by graphene oxide was stated. Considering biocompatibility of the both types of carbon-based nanomaterials, they can be potentially used in future as contrast agents for bio-imaging and theranostic applications.
THERMOPHYSICS 2019: 24th International Meeting of Thermophysics and 20th Conference REFRA, 2019
Features of heat transport in silicon-based porous structures with different morphology before an... more Features of heat transport in silicon-based porous structures with different morphology before and after thermal annealing are investigated. Specifically, fractal-like porous silicon and silicon nanowire arrays samples were considered. All the structures were annealed in dry air at various temperatures in diapason from 600 °C up to 1000 °C for 20 minutes. The photoacoustic technique with gas-microphone registration was applied for the thermal diffusivity evaluation of the samples. Particularly, the amplitude frequency dependencies of photoacoustic response from the considered samples in the classical gas-microphone configuration were measured in the range from 10 Hz to 3 kHz. The simulation of the experimental dependencies with the use of appropriate model allowed us to evaluate thermal conductivity. It was found that the short time thermal annealing together with increasing annealing temperature leads to significant reduction of thermal transport in mesoporous silicon. On the opposite, the thermal properties of silicon nanowires remain unaffected.
Features of thermal transport in multilayered porous silicon nanostructures are considered. Such ... more Features of thermal transport in multilayered porous silicon nanostructures are considered. Such nanostructures were fabricated by electrochemical etching of monocrystalline Si substrates by applying periodically changed current density. Hereby, the multilayered structures with specific phononic properties were formed. Photoacoustic (PA) technique in gas-microphone configuration was applied for
Combined photothermoacoustic and photoelectric microscopy is used to investigate silicon-based st... more Combined photothermoacoustic and photoelectric microscopy is used to investigate silicon-based structures: an epitaxially grown n-type region in a p-type substrate, a p-p + interface obtained by implanting boron ions, and a region near a crack tip. It is concluded that the visualization of epitaxial regions by thermal waves most probably stems from the elastic stresses appearing during fabrication of the structures. It is shown that the spatial distribution of the elastic stresses appearing upon ion implantation is visualized by thermal waves. In the region near the crack tip inhomogeneities in the thermoelastic and energy properties extending over hundreds of microns can be diagnosed by thermal waves and electron-hole plasma waves. Spatial periodicity with a period ∼85 m is discovered in the variation of the thermoelastic properties near the crack tip.
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Papers by Andrey Kuzmich