Исследование плазмонного резонанса в Bi-=SUB=-2-=/SUB=-Se-=SUB=-3-=/SUB=- и Sb-=SUB=-2-=/SUB=-Te-=SUB=-3-=/SUB=- методом инфракрасной спектральной эллипсометрии

In the infrared region of the spectrum (IR), the optical properties of single-crystal samples of narrow-gap degenerate semiconductors Bi2Se3 and Sb2Te3 are investigated by infrared spectral ellipsometry (SE). The transport properties of the Drude fitting of dielectric functions obtained by spectroscopic ellipsometry are studied. The behavior of the bulk and surface plasmon polaritons is investigated in detail. The dispersion and mean free path of the plasmon, the depth of the skin layer for the conducting and dielectric surfaces are calculated. The contribution of the plasmon to the optical properties is estimated from the spectral density for the Bi2Se3 and Sb2Te3 samples.

Optical Parameters of As-Deposited and Annealed (Ga0.3In0.7)2Se3 Thin Films

The (Ga0.3In0.7)2Se3 films deposited by the thermal evaporation technique are annealed in the inert atmosphere (argon) for 1 h at temperatures of 50, 100, and 150 ∘C. The spectral ellipsometry is applied for measuring the spectral dependences of the refractive and extinction coefficients of as-deposited and annealed (Ga0.3In0.7)2Se3 films. The optical transmission spectra, as well as the optical absorption spectra of (Ga0.3In0.7)2Se3 films, are studied depending on the annealing temperature. The optical absorption edge for annealed (Ga0.3In0.7)2Se3 films is shifted to the short-wavelength region and broadens, as the annealing temperature increases. Parameters of the Urbach absorption edge are determined for as-deposited and annealed (Ga0.3In0.7)2Se3 films. The spectral dependences of the refractive index are analyzed in the framework of the Wemple–DiDomenico model. The nonlinear increase of the energy pseudogap, Urbach energy, and refractive index with the annealing temperature are revealed.

Activation of film growth on indium phosphide by pulsed photon treatment

Photon activation of various physicochemical processes by the radiation of powerful pulsed xenon lamps (radiation range of 0.2-1.2 µm) is one of the promising areas of material science. The aim of this study was to determine the effect of preoxidative pulsed photon treatment on the process of thermal oxidation of indium phosphide with a nanosized layer of V2O5 on the surface, as well as its effect on the composition and morphology of the formed films. We determined the optimal mode of pre-oxidative pulsed photon treatment of magnetron-formed V2O5/InP heterostructures with a radiation density of 15 J/cm2. By laser and spectral ellipsometry methods, photon activation of V2O5/InP before thermal oxidation was found to increase the thickness of the formed films practically twofold. X-ray diffraction analysis confirms the intensification of the phosphate formation process. The morphological characteristics of the films were determined by atomic force microscopy.Pre-oxidative pulsed photon treatment with an optimal radiation density of 15 J/cm2 activates the thermal oxidation of V2O5/InP heterostructures. It is associated with the formation of new active centres and accelerated rearrangement of chemical bonds in the intermediate complexes of the V2O5 catalyst with semiconductor components

Processes of electroluminescence degradation of light-emitting structures based on thin silicon oxide and nitride films

SiO2 /Si, SiN1.2/SiO2 /Si and SiO2 /SiN0.9/SiO2 /Si structures have been fabricated by chemical vapor deposition and thermal oxidation of silicon. The elemental composition and thicknesses of dielectric layers have been studied using Rutherford backscattering spectroscopy, scanning electron microscopy, and spectral ellipsometry. The electroluminescence (EL) of the samples has been investigated in the “electrolyte–dielectric–semiconductor” system at a positive bias voltage applied to the silicon substrate. An intense band with maxima at 1.9 eV appears on the EL spectra of the SiO2 /Si sample, while the EL spectra of the SiN1.2/SiO2 /Si and SiO2 /SiN0.9/SiO2 /Si samples are characterized by the presence of bands with the maximum values of 1.9, 2.3 and 2.7 eV. The nature of these bands is discussed. Passing a charge in the range of 100–500 mC/ cm2 through the SiO2 /SiN0.9/SiO2 /Si sample, an increase in the EL intensity was recorded in the entire visible range. Passing a charge of 1 C/cm2 through a sample with a three-layer dielectric film resulted in the EL intensity decrease. It can be explained by the upper oxide layer degradation. It has been shown that silicon nitride deposited on top of the SiO2 layer protects the oxide layer from field degradation and premature breakdown. The most stable electroluminescence when exposed to a strong electric field is observed for the structure SiN1.2/SiO2 /Si.

Surface structure of Gd20Co80 alloy

Gd 20 Co 80 alloy was studied applying experimental methods of spectral ellipsometry, atomic force and scanning tunneling microscopy. The experimental results exhibit the eutectic two-phase structure of this alloy. Clusters of a phase with a lower content had a lesser concentration of free carriers, which resulted in smaller tunnel currents during the measurements. To analyze the experimental data, a theoretical approach was developed, which was based both on the quantum-mechanical methods of configurational interaction and on three-diagonal Toeplitz matrices formalism. This approach allowed us to describe in detail the energy bands formation process in solid clusters with a relatively small quantity of atoms, which as a consequence enabled to describe the Shockley surface states as well as the existence of a surface layer with partially formed energy bands. Spectral-ellipsometric measurements of Gd 20 Co 80 alloy thin films confirmed a significant difference between the measured optical constants for 20-nm thick films and larger films. Quantum-mechanical molecular calculus allowed to obtain optical constants for several supercells of Gd-Co chemical compounds and confirmed the acquired experimental and theoretical results.

Study of composite TiN/Ag/Cu2O/TiO2 with improved photocatalytic performance

TiO2 film has the advantage of good photochemical stability and it can be used for self-cleaning glasses. However, due to the wide band gap, the spectral response range of TiO2 film is restricted to the ultraviolet region. In this work, based on the research of TiO2 thin films, multilayer TiN/Ag/Cu2O/TiO2 films were designed and successfully prepared. The structure and properties of the obtained samples were characterized by X-ray diffraction, spectral ellipsometry (SE), atomic force microscopy (AFM) and UV-Vis-NIR spectrophotometer. The results show that p-n heterojunction will be formed between Cu2O and TiO2 in the multilayer film, thus reducing the band gap of TiO2 film. Based on the analysis of the photocatalytic mechanism of the multilayer films, a conclusion may be drawn that the designed multilayer film is helpful to improve the photocatalytic efficiency of titanium dioxide and expand its utilization of sunlight.

Самоорганизация состава пленок Al-=SUB=-x-=/SUB=-Ga-=SUB=-1-x-=/SUB=-N, выращенных на гибридных подложках SiC/Si

Using spectral ellipsometry, Raman spectroscopy, and scanning microscopy with an X-ray spectrometer (EDS), the phenomenon of self-organized change in the composition of AlxGa1-xN epitaxial layers during their growth by chloride-hydride epitaxy (EDX) on SiC / Si (111) hybrid substrates was revealed. It was found that during the growth of AlxGa1-xN layers with a low, about 11-24% Al content, interlayers (domains) appear, consisting of AlGaN stoichiometric composition. A qualitative model has been proposed, according to which self-organization in composition arises due to the effect of two processes on the growth kinetics of the AlxGa1-xN film. The first process is associated with the competition of two chemical reactions proceeding at different rates. One of these reactions is the AlN formation reaction; the second is the reaction of GaN formation. The second process, closely related to the first, is the appearance of elastic compressive and tensile stresses during the growth of AlxGa1-xN films by the CGE method on SiC / Si (111). Both processes influence each other, which leads to a complex pattern of aperiodic changes in the composition over the thickness of the film layer. Keywords: A3B5 compounds, wide-gap semiconductors, AlGaN, AlN, GaN, silicon carbide on silicon, self-organization of the composition, HVPE method, solid solutions, heterostructures.

Особенности деформирования круглых тонкопленочных мембран и экспериментальное определение их эффективных характеристик

The features of thin-film membranes, which are formed above round holes in silicon substrates using the Bosch-process are considered. The membrane has a complex shape due to the presence of the stress state of the initial films. The analysis of the dependence of the membrane deflection w on the supplied overpressure P is used to calculate the mechanical characteristics of the membranes. In this case, it is necessary to determine directly on the membrane its diameter, the thickness of the constituent layers, the change in the relief of the membrane surface over its entire area as the excess pressure P. Determination of the membrane diameter and the thicknesses of the constituent layers is shown by the example of p-Si*/SiNx/SiO2 and SiNх/SiО2/SiNх/SiО2 membranes. We used spectral ellipsometry, energy-dispersive X-ray spectroscopy, optical profilometry, optical microscopy. The influence of the peculiarities of the fixing conditions on the stress-strain state of membranes is shown, and the assessment is carried out by means of numerical modeling. A technique has been developed for measuring and calculating the mechanical characteristics of membranes that have an initial deflection. The calculation result is shown on the example of a membrane with an initial deflection of 2 µm – SiNх/SiО2/SiNх/SiО2 and a membrane with an initial deflection of 30 µm – Al/SiO2/Al.

Atomic Structure and Optical Properties of Plasma Enhanced Chemical Vapor Deposited SiCOH Low-k Dielectric Film-=SUP=-*-=/SUP=-

The SiCOH low-k dielectric film was grown on Si substrate using plasma enhanced chemical vapor deposition method. Atomic structure and optical properties of the film were studied with the use of X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) absorption spectroscopy, Raman spectroscopy and ellipsometry. Analysis of XPS data showed that the low-k dielectric film consists of Si-O4 bonds (83%) and Si-SiO3 bonds (17%). In FTIR spectra some red-shift of Si-O-Si valence (stretching) vibration mode frequency was observed in the low-k dielectric film compared with the frequency of this mode in thermally grown SiO2 film. The peaks related to absorbance by C-H bonds were observed in FTIR spectrum. According to Raman spectroscopy data, the film contained local Si-Si bonds and also C-C bonds in the s-p3 and s-p2 hybridized forms. Scanning laser ellipsometry data show that the film is quite homogeneous, homogeneity of thickness is ~ 2.5%, and homogeneity of refractive index is ~ 2%. According to analysis of spectral ellipsometry data, the film is porous (porosity is about 24%) and contains clusters of amorphous carbon (~ 7%).