Silicon-germanium alloy films were formed by electrochemical deposition of germanium into porous silicon matrices with thicknesses varying from 1.5 to 10 mu m followed by subsequent rapid thermal processing at 950 degrees C in an inert atmosphere. Study of the fabricated structures using SEM and Raman spectroscopy, as well as measurements of their electrical conductivity and thermoelectric properties revealed that the highest Seebeck coefficient (-505 mu V/K at 450 K) and Power Factor (1950 mu W/(m & sdot;K2) at 400 K) values were obtained when a 5 mu m-thick porous silicon was used as a structural matrix. Under such conditions, an optimal balance between electrical conductivity, structural disorder and electrical insulation from the substrate is achieved due to the presence of a residual porous underlayer, making it possible to maximize the film's thermoelectric performance. The obtained silicon-germanium alloy films are deemed suitable for the fabrication of both discrete and integrated thermoelectric devices based on monocrystalline silicon substrates.

Thermoelectric materials based on cobalt-containing SiGe alloy films were fabricated using monocrystalline silicon wafers with thin porous silicon layers electrochemically decorated with cobalt nanoparticles, filled germanium and subsequently subjected to rapid thermal processing. SEM, XRD, Raman spectroscopy and measurements of electrical conductivity and thermoelectric parameters revealed that an intermediate silicidization step involving thermal processing at 850 degrees C after cobalt deposition is crucial to maximize the resulting alloy's thermoelectric capabilities. The obtained silicidized SiGe:Co samples demonstrate a Seebeck coefficient of -450 mu V/K and an estimated figure-of-merit ZT value of up to 0.72 at 450 K due to the presence of crystalline cobalt silicides in the film. These results enable a new approach to the fabrication of thin film thermoelectric materials based on SiGe alloys.

Film structures based on Si1–xGex (0 < x < 1) solid solutions are currently obtained by chemical-vapor-deposition methods. For device application of the obtained structures, it is necessary to know the electrical properties of the material synthesized under different conditions. In this work, we carry out galvanomagnetic studies of the electrical conductivity in porous and solid Si1–xGex films, as well as the concentration and mobility of the majority charge carriers in them at a temperature of 30–300 K. It is shown that, as in pure silicon and germanium of comparable porosity, the electrical conductivity in the studied samples can be considered as in a medium with voids. It is established that the type of majority charge carriers in the alloy is determined by the type of silicon substrate used. This is practically important for creating both arms of a thermoelectric converter, which makes the method for producing Si1–xGex(0 < x < 1) alloy promising for device applications, in particular in thermoelectric converters and lithium-ion batteries.

Using photoluminescence and Raman spectroscopy, as well as high-resolution transmission microscopy and X-ray diffraction, germanium nanowires obtained by cathodic deposition from an aqueous solution of germanium dioxide were studied during their annealing by a laser at 720 °C under ambient conditions. It is established that the dynamics of Raman and photoluminescence spectra are related to the oxidation of wires during such annealing. The study showed that vacuum annealing of as-grown nanowires at 600 °C for 30 min suppresses laser high-temperature germanium oxidation. The observed effect is associated with the saturation of vacancies in the surface germanium suboxide with indium atoms used as a catalyst in the formation of nanowires.

Using solid-phase and molecular-beam epitaxy methods at 350°C, polycrystalline and epitaxial films of iron monosilicide (FeSi) with a thickness of 3.2 to 20.35 nm were grown on a Si(111) substrate, which was confirmed by X-ray diffraction data. Morphological studies have shown that the films are continuous and smooth with a root-mean-square roughness of 0.4–1.1 nm when grown by solid-phase epitaxy, and in the case of molecular beam epitaxy, they have an increased roughness and consist of coalesced grains with sizes up to 1 μm and a puncture density up to 1 × 107 cm–2. In solid-phase epitaxy, an increase in thickness leads to incomplete silicide formation and the appearance of a layer of disordered iron monosilicide with a thickness of 10 to 20 nm. This is confirmed by a change in the temperature dependence of resistivity ρ from semiconductor to semi-metallic and a decrease in resistivity by one and a half to two times. The nonmonotonic nature of the temperature dependence of the resistivity ρ ultrathin FeSi film with a thickness of 3.2 nm has been established, in which a maximum at 230–240 K, a region of growth from 160 to 65 K with Eg = 14.8 meV and further growth without saturation to a temperature of 1.5 K are observed. With increasing thickness of FeSi films grown by molecular-beam epitaxy, the minimum and maximum are not observed, but the tendency of nonmonotonic growth of ρ(T) with decreasing temperature and the opening of the band gap Eg = 23 meV remains. The probable reasons for the occurrence of effects in the dependences ρ(T) are considered. In ultrathin and thin FeSi films grown by solid-phase and molecular-beam epitaxy, respectively, an anomalous Hall effect was found, which was confirmed by the weak ferromagnetic properties of the films. The results obtained proved the possibility of growing and controlling the properties of ultrathin and thin FeSi films on silicon obtained by solid-phase and molecular-beam epitaxy, which ensured the appearance of their unique transport and magnetic properties that are absent in single crystals.

Mg2Si film 350–600 nm thick was formed on Si(111) substrate by ultrafast reactive deposition of Mg. Then 10–15 nm thick films of FeSi or CrSi2 were grown as cover layers on Mg2Si by codeposition of Fe/Si or Cr/Si. In comparison with bare Mg2Si/Si film, the measured transparency losses in 0.1–1.1 eV range are ∼17–25 and 10–35

Morphology and crystalline structure of silicon-germanium alloys formed by rapid thermal processing of germanium-filled porous silicon layers are evaluated. Two types of porous silicon are employed as matrices for electrochemical pore filling using GeO2 aqueous solutions and subsequently compared, the first one formed by electrochemical anodization and the second by silver-assisted chemical etching of monocrystalline silicon. The resulting alloys' structure and composition are investigated using scanning electron microscopy, energy -dispersive X-ray analysis, Raman spectroscopy and X-ray powder diffraction. It is shown that by varying the porosity of the initial matrix (by adjusting anodization current density for anodic porous silicon or changing silver deposition time for structures produced by metal-assisted etching) in the range from 55 to 75%, Si1-xGex alloys with germanium fractions of x = 0.31 to x = 0.83 can be formed, as indicated by Raman spectroscopy. It is concluded that composition-adjustable layers of silicon-germanium can be successfully formed on either type of porous silicon layer. While an increase in porosity generally leads to a decrease in silicon fractions in the alloy, the steepness of this effect varies heavily depending on the type of porous matrix used and should be considered independently for anodic porous silicon and silicon nanowires.

Continuous and porous films of Si _1-x Ge _x alloys with a germanium content of about 40 % and a thickness of 3–4 μ m formed on single-crystal silicon by electrochemical deposition into the porous silicon matrix with a subsequent rapid thermal annealing at a temperature of 950 ^∘ C have been investigated by the Raman scattering spectroscopy and scanning electron microscopy methods. Based on the spectra in the Stokes and anti-Stokes frequency bands with the use of the Boltzmann statistics and the Fourier thermal conductivity law, the film thermal conductivity coefficients have been determined; their values are 7–9 and 3–6 W/(m K) for the continuous and porous films, respectively. The low thermal conductivity of the porous film is explained by an additional phonon scattering at a developed surface of pores. The possibility of application of such films in thermoelectric converters is provided by the simplicity and scalability of the procedure of alloy producing and its low thermal conductivity

Epitaxial and polycrystalline films of iron (Fe), chromium (Cr), and calcium (Ca) silicides of various thicknesses (from 3.2 to 380 nm) were grown on silicon and sapphire substrates in ultrahigh vacuum by three methods (solid-phase epitaxy, reactive epitaxy and molecular beam epitaxy). The crystal structure and matching with the silicon lattice were determined for them using the X-ray diffraction method. A comparative analysis of Raman scattering spectra and far-IR spectroscopy spectra showed that films of semiconductor silicides have the strongest Raman peaks, and the detected shifts in their positions are caused by distortions in the silicide lattices. It has been established that in films of iron and chromium monosilicides at a fixed laser excitation wavelength ( λ=628.3 nm) and a power of 3.4 mW, the strength of the Raman peaks decreases with decreasing film thickness and they disappear completely at a thickness below 10 nm. Chromium trisilicide films were grown on single-crystal sapphire, which made it possible for the first time to detect for it active Raman phonons at λ=488 nm and a power of 0.42 mW at wave numbers 214.3 and 273.1 cm ^-1 . The studied films of transition metal monosilicides are of significant interest from the perspective of their possible use as materials for thermoelectronics and spintronics, and systematized information on active Raman phonons and IR active phonons will make it possible to quickly determine the type of phase formed immediately after film growth.

In this study, the formation, crystal structure, optical and thermoelectric properties of ultrathin (UT) films of iron and chromium monosilicides are considered, which exhibit optical and thermoelectric properties characteristic of semimetals with a low density of states near the Fermi level and the main contribution of holes to the Seebeck coefficient in the temperature range 120-400 K and the transition to its negative values at T > 400 K. The power factor for FeSi and CrSi UT films versus temperature was calculated and ab initio calculations of the phonon structure and thermal conductivity for bulk FeSi and its nanowires were carried out, which made it possible to estimate the thermoelectric figure of merit of ultrathin FeSi films.

Сплошные и пористые плёнки сплавов Si1-xGex с содержанием германия около 40 % и толщиной 3-4 мкм, сформированные на монокристаллическом кремнии методом электрохимического осаждения германия в матрицу пористого кремния с последующим быстрым термическим отжигом при температуре 950 °C, исследованы методами спектроскопии комбинационного рассеяния света (КРС), оптической спектроскопии и сканирующей электронной микроскопии. На основе спектров, снятых в стоксовой и антистоксовой областях частот с использованием статистики Больцмана и закона теплопроводности Фурье, определены коэффициенты теплопроводности плёнок, которые составляют 7-9 и 3-6 Вт / (м ⋅ К) для сплошной и пористой плёнок соответственно. Низкая теплопроводность пористой плёнки объясняется дополнительнымфононным рассеянием на развитой поверхности пор. Перспективность применения таких плёнок в термоэлектрических преобразователях обеспечивается простотой и масштабируемостью способа изготовления сплава, а также его низкой теплопроводностью. Solid and porous films of the Si 1-xGex alloys with a germanium content of about 40% and a thickness of 3-4 μm, formed on single-crystal silicon by electrochemical deposition of germanium into a porous silicon matrix followed by rapid thermal annealing at a temperature of 950 °C, are studied by Raman spectroscopy, optical spectroscopy, and scanning electron microscopy. Based on the Raman spectra taken in the Stokes and anti-Stokes frequency regions, using Boltzmann statistics and the Fourier thermal conductivity law, the thermal conductivity of the films is determined, which is found to be 7-9 and 3-6 W/(m×K) for a continuous and porous film, respectively. The low thermal conductivity of the porous film is explained by additional phonon scattering from the developed pore surface. The prospect of using such films in thermoelectric converters is ensured by the simplicity and scalability of the method for manufacturing the alloy, as well as its low thermal conductivity.

Continuous and porous films of Si(1-x)Ge(x )alloys with a germanium content of about40%and a thickness of 3-4 mu m formed on single-crystal silicon by electrochemical deposition in to the porous silicon matrix with a subsequent rapid thermal annealing at a temperature of 950(degrees)Chave been investigated by the Raman scattering spectroscopy and scanning electron microscopy methods. Based on the spectra in the Stokes and anti-Stokes frequency bands with the use of the Boltzmann statistics and the Fourier thermal conductivity law, the film thermal conductivity coefficients have been determined; their values are 7-9 and 3-6 W/(m K) for the continuous and porous films, respectively. The low thermal conductivity of the porous film is explained by an additional phonon scattering at a developed surface of pores. The possibility of application of such films in thermoelectric converters is provided by the simplicity and scalability of the procedure of alloy producing and its low thermal conductivity

The magnetic properties of nanoobjects of nonmagnetic substances based on silicon and transition metal (iron) are considered. It is found that a system of α -FeSi _2 nanorods with a mean height of 6.6 nm and lengths from 50 to 200 nm is formed by deposition of iron with 5.22 monolayers in ultrahigh vacuum on a vicinal silicon surface Si(111)-4 ^∘ followed by annealing at a temperature of 630^∘ C. Soft ferromagnetic loops with a coercive force from 90 to 180 Oe, which persist up to a temperature of 300 K, are observed in nanorods. It is found that easy magnetization axis is perpendicular to the nanorods, while the hard magnetization axis is parallel to them. This type of nanoobjects is promising for developing spintronic devices within the planar silicon technology.

Platinum nanoparticles were prepared on silicon substrates at room temperature using electroless deposition with different durations from 1 to 40 min. The effect of deposition times on the morphology and composition of the deposited Pt particles and porous films was examined using scanning, transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and Raman scattering. Moreover, atomic force microscopy was used to examine the structural properties and morphological characterization of the deposed particles. The wetting properties of the por-Si/Pt structure were investigated using the sessile drop method. The research indicates that the por-Si/Pt structure has uniformly distributed nonspherical self assembled Pt particles with a height of up to 120 nm and a diameter of 200 nm. The concentration of these particles is 2.5 x 109 cm-2 and there is a mesoporous silicon layer with a thickness up to 580 nm. A uniform size distribution of the particles is achieved after 1 min of deposition. The conditions for creating the por-Si/Pt structure, characterized by a high Pt particle concentration and coverage, have been identified. The morphology parameters of the particles and layers depend on the duration of the deposition. The evolution of the formation of an array of platinum particles, meso-and macroporous silicon, including all stages of growth of the components of the Por-Si/Pt structure was established.

The formation of thin films of indium antimonide on Si(111) from a stoichiometric mixture with a thickness of 32–48 nm was performed by solid-phase epitaxy (SPE) at a temperature of 320–380°C under ultrahigh vacuum conditions. It is shown that the use of an array of high-density InSb seed islands makes it possible to form a large-block epitaxial InSb film, while a solid-phase epitaxy from a mixture deposited on a clean surface produces a granular polycrystalline film. Based on the analysis of low energy electron diffraction patterns, X-ray diffraction data and Raman spectra, the stresses in the resulting films were determined: in the out of plane direction the films are weakly compressed by 0.1–0.14

In this paper, we report on optimizing the conditions for subsequently growing single-phase films of calcium monosilicide (CaSi) and calcium disilicide (CaSi2) on single -crys-tal silicon by reactive deposition epitaxy (RDE) and molecular beam epitaxy (MBE). The tem-perature range for the growth of CaSi films (400-500 degrees C) was determined, as well as the tem-perature range (600-680 degrees C) for the growth of CaSi2 films on silicon with three orientations: (111), (100) and (110). The minimum temperatures for the epitaxial growth of CaSi films by the RDE method and CaSi2films by the MBE method were determined, amounting to, respec-tively, T = 475 degrees C and T = 640 degrees C. An increase in the ratio of Ca to Si deposition rates to 26 made it possible to grow a large-block CaSi2 epitaxial film with the hR6 structure by the MBE method at T = 680 degrees C. Raman spectra and reflection spectra from single-phase epitaxial CaSi and CaSi2 films on silicon were recorded and identified for the first time. The correspondence between the experimental reflection spectra and the theoretically calculated reflection spectra in terms of amplitude and peak positions at photon energies of 0.1-6.5 eV has been established. Single-phase CaSi and CaSi2 films retain transparency in the photon energy range 0.4-1.2 eV.

The solid-state formation of gallium antimonide on Si(111) from a stoichiometric mixture of GaSb in the temperature range of 300 °C–500 °C and thicknesses of 12–40 nm was studied under ultrahigh vacuum conditions. The influence of the preformed GaSb seed islands on the morphology, composition, and structure was studied. It has been found that at 300 °C a strained continuous polycrystalline film is formed, which rupture at 350 °C. It has been shown that a continuous single-crystal GaSb film grows at 400 °C–500 °C if the sample is annealed at a weak antimony flow. This is also facilitated by the preliminary formation of a high density of nanosize GaSb seed islands. As a result, a continuous relaxed film with epitaxial relations GaSb(111)∣∣Si(111) and GaSb[1–10]∣∣Si[1–10] was obtained from a GaSb mixture 40 nm thick at 500 °C. We demonstrate a possibility of direct formation of GaSb on Si(111) without buffer layers of other chemical elements.

A nanocrystalline Ca 2 Si film on Al 2 O 3 (0001) is formed for the first time by converting a sacrificial 2D Mg 2 Si template into a Ca 2 Si seed layer with the preliminary formation of an amorphous 2D silicon layer. A Ca 2 Si seed layer on a sapphire substrate facilitates the growth of oriented Ca 2 Si films by molecular-beam epitaxy (MBE) at a temperature of 250°C, for which one epitaxial ratio is observed, Ca 2 Si(211)/Al 2 O 3 (0001). Studies of the optical properties and parameters of the band structure of Ca 2 Si on sapphire reveal the nature of the fundamental direct transition with an energy of 0.88 ± 0.01 eV. Direct interband transitions are observed in the band structure of Ca 2 Si: at 0.88, 1.16, 1.49, and 1.61 eV with increasing oscillator strength. At photon energies from 0.78 to 0.88 eV, the Urbach tail on defects in Ca 2 Si nanocrystals makes the main contribution to absorption. Absorption at grain boundaries is observed at photon energies from 0.6 to 0.78 eV, and at free carriers, at energies below 0.6 eV. The results obtained are important for optoelectronics in the infrared (IR) region of the spectrum.