A technique has been developed for frequency analysis of the IR reflection spectrum to determine the thickness and order of the layers in the epitaxial structure of silicon carbide. Calculations for the 4H-SiC epitaxial structure have been performed. The method has been shown to be highly sensitive to optical boundaries resulting from a sequential increase in the doping level during the layer growth. Keywords: Silicon carbide, epitaxial layer, IR reflection, spectrum

The significant technology progress for fabrication of semiconducting CVD diamonds poses an important task of developing a precise and non-destructive method for estimation the boron content in epitaxial layers. We propose a novel two-step technique to determine the boron concentration in homoepitaxial diamond layers from FTIR measurements. The essence of the method is to evaluate the epilayer thickness from reflectance spectra at the first step, and to recalculate and analyze FTIR spectra in terms of effective optical density at the second step. Spectra are divided into 3 wavelength regions with accurate accounting of passing radiation through a multilayered structure with different thicknesses of absorbing media for various absorbing mechanisms. We have demonstrated the benefit of the method for a set of samples with CVD homoepitaxial layers grown on various HPHT substrates. The data obtained from FTIR spectra are thoroughly compared to the charge carrier concentration derived from electrical capacitance–voltage measurements.

Silicon carbide (SiC) is a wide-band gap semiconductor that exceeds other semiconducting materials (except diamond) in electrical, mechanical, chemical, and radiation stability. In this paper, we report a novel approach to fabrication of SiC nano films on a Si substrate, which is based on the endotaxial growth of a SiC crystalline phase in a graphite-like carbon (GLC) matrix. GLC films were formed by carbonization of rigid rod polyimide (PI) Langmuir-Blodgett (LB) films on a Si substrate at 1000 degrees C in vacuum. After rapid thermal annealing of GLC films at 1100 degrees C and 1200 degrees C, new types of heterostructures SiC(10 nm)/GLC(20 nm)/Si(111) and SiC(20 nm)/GLC(15 nm)/SiC(10 nm)/Si(111) were obtained. The SiC top layer was formed due to the Si-containing gas phase present above the surface of GLC film. An advantage of the proposed method of endotaxy is that the SiC crystalline phase is formed within the volume of the GLC film of a thickness predetermined by using PI LB films with different numbers of monolayers for carbonization. This approach allows growing SiC layers close to the 2D state, which is promising for optoelectronics, photovoltaics, spintronics.

A set of efficient operational methods for post-growth determination of the kinetic parameters of charge carriers and impurity concentration in silicon carbide and diamond substrates and epitaxial layers, as well as layer thicknesses, by analyzing infrared (IR) reflection and absorption spectra, is presented.

Silicon carbide SiC is the basic material of modern extreme and power electronics. The characterization of substrates and SiC-based epitaxial multilayers requires advanced on-line control methods to be developed. In this study, contactless nondestructive optical methods for controlling the kinetic parameters of carriers, layer thickness, and surface quality are demonstrated. Techniques based on the physical processes of the interaction between a photon flux and a SiC single crystal are used. The carrier density and mobility and layer thicknesses in epitaxial multilayers are determined and the substrate surface-treatment quality is characterized by approximating infrared reflectance spectra. The data obtained are verified by independent methods. The proposed algorithm for combined use of these methods ensures the efficient control of substrates and epitaxial compositions along with reproducible characteristics and functional parameters.

The paper introduces a method of determining thicknesses of single- and multi-layer silicon carbide structures using infrared reflection spectrum frequency analysis. Spectrum waveform is affected by spectral interference in layers or groups of layers. LabView software package offered a solution to perform spectral analysis. The results are provided both for model structures and experimental spectra. Model structure’ reflection spectrum was evaluated using a dielectric function that took into account the response of lattice vibrations and free charge carriers. Experimental spectra were obtained from a real multilayer structure manufactured for power electronics devices.

Разработана методика частотного анализа ИК спектра отражения для определения толщин и порядка расположения слоев в эпитаксиальной структуре (ЭС) карбида кремния, выполнены расчеты для 4H-SiC ЭС, показана высокая чувствительность метода к оптическим границам, возникшим в результате последовательного увеличения уровня легирования в процессе роста слоя.

Разработана методика определения толщин после получения одно- и многослойных карбидкремниевых структур методом частотного анализа спектра инфракрасного отражения, на форму которого влияет спектральная интерференция в слоях и группах слоев. Анализ спектра выполнен в программном пакете LabView. Представлены результаты, полученные как для модельных структур, расчетный спектр отражения которых определялся с использованием диэлектрической функции, учитывавшей реакцию колебаний решетки и свободных носителей заряда, так и для экспериментальных спектров реальных многослойных структур приборов силовой электроники. Ключевые слова: слой, отражение, интерференция, спектр.

The influence of the anodization current density to the morphology and composition of the surface of porous silicon before and after its impregnation with an antibiotic was investigated using atomic force microscopy and IR spectroscopy. Layers of porous silicon were obtained by electrochemical etching; variable technological parameters of anodizing were the current density and the type of conductivity of the silicon plate. The results obtained are discussed in terms of their use in targeted drug delivery.

In this paper, we propose a model for the quantitative analysis of the dependence of the dielectric function of hexagonal silicon carbide polytypes on the photon energy in the range 0.0–6.5 eV. This model consists of the sum of two Tauc-Lorentz oscillators (main and minor) with a total band gap. This approach is used to describe the three hexagonal polytypes of silicon carbide 4H, 15R, 6H obtained in one growth process. Both C-faces and Si-faces of each polytype are analyzed. A number of conclusions have been made about the dependence of the oscillator parameters on the polytype hexagonality degree and the type of surface face. The strongest dependence is an increase of the minor oscillator amplitude with an increase of polytype hexagonality degree. It should also be noted that the band gap increases upon transition from the C-face (0001 ̅) to the Si-face (0001).

A model is suggested for a quantitative analysis of the dependence of the dielectric function of hexagonal silicon carbide polytypes on photon energy in the range of 0.7–6.5 eV. The model, which is the sum of two Tauc–Lorentz oscillators (main and minor) with a common energy gap, is used to describe three hexagonal silicon carbide polytypes (4H, 15R, 6H) obtained in the same growth process. Both C- and Si-faces of each polytype are analyzed. A number of conclusions are drawn about how the oscillator parameters depend on the degree of hexagonality of a polytype and on the type of a surface face. The strongest dependence is that the amplitude of the minor oscillator grows with increasing degree of hexagonality of a polytype. The increase in the energy gap on passing from the C-face (000$$\bar {1}$$) to the Si-face (0001) is also worthy of note.

This paper presents the results of a nanoindentation study of the hardness and Young’s modulus of hexagonal silicon carbide SiC-4H, obtained by the modified Lely method, in thin surface layers near the C-terminated and Si-terminated faces at small penetration depths of the indenter. It is shown that differences in the elastic properties and hardness of SiC propagate from the surface into the crystal to a depth of about 60 nm. The Young's modulus at the C-terminated face practically coincides with the Young's modulus of the bulk SiC-4H sample (~ 400 GPa), which is approximately 2.3 times higher than the Young's modulus at the Si-terminated face at a depth of 0 to 35 nm (~ 170 GPa). The value of the SiC hardness is approximately 1.5 times higher at the surface of the C-terminated face than at the Si-terminated face, on average, at a depth of 0 to 60 nm. It is concluded from the obtained data that the surface energy of the C-terminated face is also approximately 1.5 times higher than the surface energy of the Si-terminated face since a new surface is formed upon deformation or cracking of the crystal

The results of hardness and Young’s modulus study of near-surface layers of 4H-SiC hexagonal silicon carbide obtained by the modified Lely method from the C-face (000$$\bar {1}$$) and Si-face (0001) at shallow depths of the indenter are presented. It is shown that the differences in the elastic properties and hardness of SiC propagate from the surface into the crystal at a depth of about 60 nm. The Young’s modulus at the C-face almost coincides with the Young’s modulus of the bulk 4H-SiC sample (~ 400 GPa), which is approximately 2.3 times higher than the Young’s modulus at the Si-face at a depth of 0–35 nm (~170 GPa). The hardness coefficient of SiC is on average about 1.5 times higher at the surface of the C-face (000$$\bar {1}$$) than at the Si-face (0001) at a depth of 0–60 nm. Since a new surface is formed upon deformation or destruction of the crystal (formation of cracks), based on the data obtained, it is concluded that the surface energy of the C-face is also about 1.5 times higher than the surface energy of the Si-face.

Silicon carbide substrates and epitaxial structures are investigated by nondestructive contactless methods. Parameters of the disrupted surface layer and roughnesses are determined using ellipsometry and atomic force microscopy. The free charge carrier concentration is determined by IR spectroscopy. The thicknesses in the multilayer epitaxial structure on SiC are determined using IR spectroscopy and scanning electron microscopy.

Abstract Silicon carbide substrates and epitaxial structures are investigated by nondestructive contactless methods. Parameters of the disrupted surface layer and roughnesses are determined using ellipsometry and atomic force microscopy. The free charge carrier concentration is determined by IR spectroscopy. The thicknesses in the multilayer epitaxial structure on SiC are determined using IR spectroscopy and scanning electron microscopy.

Atomic layer deposition (ALD), a gas-phase thin film deposition technique based on repeated, self-terminating gas–solid reactions, has become the method of choice in semiconductor manufacturing and many other technological areas for depositing thin conformal inorganic material layers for various applications. ALD has been discovered and developed independently, at least twice, under different names: atomic layer epitaxy (ALE) and molecular layering. ALE, dating back to 1974 in Finland, has been commonly known as the origin of ALD, while work done since the 1960s in the Soviet Union under the name “molecular layering” (and sometimes other names) has remained much less known. The virtual project on the history of ALD (VPHA) is a volunteer-based effort with open participation, set up to make the early days of ALD more transparent. In VPHA, started in July 2013, the target is to list, read and comment on all early ALD academic and patent literature up to 1986. VPHA has resulted in two essays and several presentations at international conferences. This paper, based on a poster presentation at the 16th International Conference on Atomic Layer Deposition in Dublin, Ireland, 2016, presents a recommended reading list of early ALD publications, created collectively by the VPHA participants through voting. The list contains 22 publications from Finland, Japan, Soviet Union, United Kingdom, and United States. Up to now, a balanced overview regarding the early history of ALD has been missing; the current list is an attempt to remedy this deficiency.

High quality single crystal SiC films were prepared by carbonization of polyimide Langmuir-Blodgett films on Si substrate. The films formed after annealing of the polyimide films at 1000°C, 1100°C, 1200°C were studied by Fourier transform-infrared (FTIR) spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, transmission electon microscopy (TEM), transmission electron diffraction (TED), and scanning electron microscopy (SEM). XRD study and HRTEM cross-section revealed that the crystalline SiC film begins to grow on Si (111) substrate at 1000°C. According to the HRTEM cross-section image five planes in 3C-SiC (111) film are aligned with four Si(111) planes at the SiC/Si interface. It was shown the SiC films (35 nm) grown on Si(111) at 1200°C have mainly cubic 3C-SiC structure with a little presence of hexagonal polytypes. Only 3C-SiC films (30 nm) were formed on Si (100) substrate at the same temperature. It was shown the SiC films (30-35 nm) are able to cover the voids in Si substrate with size up to 10 μm.

The transmission spectra for the porous alumina membranes prepared by electrochemical etching were investigated in a broad wavelength range from 0.2 to 12 μm. It is shown that the spectrum of the membrane maybe divided into regions enabling characterisation of average pore size and size distribution, the membrane thickness, and the presence of residual etching agent anions.

The processes involved in the planarization of the surface of nanoporous SiO2 by the atomicmolecular deposition of nanoscale TiO2 films were studied in regimes with different degrees of penetration of TiO2 into SiO2 nanopores. The technological process parameters that correspond to different regimes of surface planarization were examined. The degree of penetration of TiO2 into SiO2 nanopores was monitored using reflection ellipsometry by measuring the depth distribution of the refraction index within the two-layer model.

The peculiarities of the formation of porous membranes based on aluminum oxide obtained by the electrochemical anodization of aluminum foil with the preset topological parameters of pores-capillares (20–220 nm) have been studied. The methods to study the membranes based on nanoporous aluminum oxide are proposed. The developed nanoporous material possesses the properties of screening IR radiation in a spectral range of 8–14 μm (corresponds to the spectral region of thermal radiation of bioobjecs). The membranes based on anodized aluminum foil provide the fulfilling the functions of channeling a high-flow helium ions with an energy of 1.5–2 MeV with the experimentally found coefficient of transmission of more than 60%.