F. A. Kuznetsov

Growth of PbS and CdS thin films by low-pressure chemical vapour deposition using dithiocarbamates

Abstract Thin films of cadmium and lead sulphides grown by chemical vapour deposition (CVD) and remote plasma enhanced chemical vapour deposition (RPECVD) using dithiocarbamates as precursors were prepared on fused silica, sapphire, (111)Si and (111)InP substrates. These films were deposited in the temperature range 473–873 K. It was established that the activation energy of the CVD process is 191.5±1.5 kJ mol −1 . The structure of polycrystalline films was halenide for PbS and wurtzite for CdS. It was also found that r.f.-plasma activation of the gas phase decreases remarkably the growth temperature and orders the film structure. RPECVD sulphide films had a high degree of preferred orientation.

Monoclinic Tungstates KDy(WO 4) 2 and KLu(WO 4) 2 - New χ( 3)-Active Crystals for Laser Raman Shifters

Efficient high-order Stokes and anti-Stokes generation in the visible and near infrared (NIR) in monoclinic KDy(WO4)2 and KLu(WO4)2 1aser host crystals by stimulated Raman scattering (SRS) and Raman-induced four-wave mixing (RFWM) were observed at 300 K for the first time in the single-pass geometry under picosecond excitation. All scattering components were identified and connected with the SRS-active vibration modes of these tungstates.

Synthesis of nanocrystalline silicon carbonitride films by remote plasma enhanced chemical vapor deposition using the mixture of hexamethyldisilazane with helium and ammonia

Abstract The silicon carbonitride films were synthesised by remote plasma enhanced chemical vapor deposition (RPECVD) using a mixture of ammonia, helium and hexamethyldisilazane Si2NH(CH3)6 as the volatile single-source precursor. Different analysis techniques such as IR, Raman spectroscopy, ellipsometry, X-ray photoelectron spectroscopy, EDS, scanning electron microscopy, high-resolution electron microscopy, selective area electron diffraction and X-ray diffraction using synchrotron radiation were used to study their physical and chemical properties. The formation of chemical bonding was shown to occur between Si, C, N atoms in the ternary compound. The chemical composition of these films depended mainly on the ammonia concentration in the gaseous phase. It was established that there is a distribution of nanocrystals in the amorphous matrix in these films.

Composition and structure of hafnia films on silicon

Ellipsometry, electron microscopy, and x-ray photoelectron spectroscopy data indicate that, during HfO2 deposition onto silicon, the native oxide reacts with the HfO2 deposit to form an amorphous intermediate layer which differs in refractive index (≃1.6) from both HfO2 (1.9–2.0) and SiO2 (1.46). Thermodynamic analysis of the Si-SiO2-HfO2-Hf system shows that Si is in equilibrium with Si/HfO2 − y only at low oxygen pressures. Starting at a certain oxygen pressure (equivalent to the formation of a native oxide layer), the equilibrium phase assemblage is Si/HfSiO4/HfO2 − y.

The investigation of properties of silicon nitride films obtained by RPECVD from hexamethyldisilazane

Abstract The silicon nitride films were obtained by remote plasma enhance chemical vapor deposition (RPECVD) using hexamethyldisilazane or its mixture with ammonia in the range 373–773 K. The correlations between the chemical composition, deposition rates, optical, electrical and structural properties and the growth conditions were established. It was found that the formation of two polycrystalline hexagonal phases SiC and Si3N4 was realized by using pure hexamethyldisilazane as precursor. The ammonia addition in gas mixture leaded to change of the chemical composition and structure of silicon nitride films, namely, the disappearance of carbon-bonding and SiC formation, and the order of hexagonal silicon nitride.

On thermodynamic equilibria of solid BN and gas phases in the B−N−H−Cl−He system

Abstract Thermodynamic analysis of the chemical vapour deposition (CVD) of boron nitride was performed for the B−N−H−Cl−He system, with new thermodynamic data for different modifications of boron nitride (hexagonal h-BN, cubic c-BN and wurtzite w-BN). The phase equilibria were calculated for the temperature region 673–2273 K, at total pressures of 1.013 × 10 3 and 1.013 × 10 5 Pa and fora wide range of atomic ratios of elements in the system. The results arc presented in the form of CVD phase diagrams which are a good way of illustrating the influence of the system parameters on the formation of stable phases. c-BN is formed in a quasi-equilibrium process at temperatures below 1804 K, the h-BN modification is most stable above this temperature, and w-BN is a metastable phase for all possible variations of the process conditions.

Chemical Composition of Boron Carbonitride Films Grown by Plasma-Enhanced Chemical Vapor Deposition from Trimethylamineborane

Boron carbonitride and boron nitride films were grown by plasma-enhanced chemical vapor deposition using trimethylamineborane and its mixtures with ammonia, hydrogen, or helium. The effects of the starting-mixture composition and substrate temperature on the chemical composition of the deposits was studied by ellipsometry, scanning microscopy, IR spectroscopy, Raman scattering, and x-ray photoelectron spectroscopy. The results indicate that the initial composition of the gas mixture, the nature of the activation gas, and substrate temperature play a key role in determining the deposition kinetics and the physicochemical properties of the deposits. Depending on these process parameters, one can obtain h-BN, h-BN + B4C, or BCxNy films.

Synthesis of silicon carbonitride dielectric films with improved optical and mechanical properties from tetramethyldisilazane

Films of silicon carbonitride have been obtained by the plasma chemical decomposition of a gaseous mixture of helium and a volatile organic silicon compound 1,1,3,3-tetramethyldisilazane (TMDS) in the temperature range of 373–973 K. The modeling of the processes of deposition from a gaseous mixture (TMDS + He) in the temperature range of 300–1300 K and pressures of Ptotal0 = 10−2–10 Torr has shown that it is possible to vary the equilibrium composition of the condensed phase depending on the synthesis temperature and the initial gaseous mixture composition. The chemical and phase compositions, as well as physicochemical and functional properties, of the films obtained in the range of 373–973 K have been studied using a complex of modern techniques, including Fourier transformed infrared (FTIR) Raman, X-ray photoelectron (XPS) and energy-dispersive spectroscopy (EDS), scanning electron (SEM) and atomic-force microscopy (AFM), X-ray diffraction using synchrotron radiation (XRD-SR), ellipsometry, and spectrophotometry. The electrophysical parameters are determined using the C-V and I-V characteristics, and the microhardness and Young’s modulus are determined by the nanoindentation method. It is established that the chemical composition of low-temperature (373–673 K) films of silicon carbonitride corresponds to a gross formula of SiCxNyOz: H, while that of high-temperature films corresponds to SiCxNy. The presence of nanocrystals with the phase composition close to the standard phase α-Si3N4 is detected in the films. It is shown that all of the films are perfect dielectrics (k = 3.8–6.4, ρ = 2.2 × 1010−1.3 × 1011 Ohm · cm), possess high transparency (∼98%) in a wide spectral range of 280–2500 nm, and have a high microhardness (3.8–36 GPa) and Young’s momentum (125–190 GPa).

Elastic and photoelastic properties of KY(WO4)2 single crystals

The complete elastic modulus matrix of a KY(WO4)2 single crystal has been determined for the first time using sound velocities measured in different directions of the crystal by a pulse-echo method. We have studied the entire isotropic part of the elasto-optic modulus matrix of KY(WO4)2 and identified high acousto-optic coupling efficiency directions. Calculated sound velocities in the three main crystallographic planes demonstrate that there are directions with considerable group velocity dispersion.

Properties of BCxNy films grown by plasma-enhanced chemical vapor deposition from N-trimethylborazine-nitrogen mixtures

Boron carbonitride films of various compositions have been grown by plasma-enhanced chemical vapor deposition using N-trimethylborazine as a single-source precursor and nitrogen as a plasma gas and an additional nitrogen source. Experiments were performed at various deposition temperatures and rf powers. The films were characterized by ellipsometry, atomic force microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, IR and Raman spectroscopies, synchrotron X-ray diffraction, energy dispersive X-ray microanalysis, and spectrophotometry. The results demonstrate that, under the conditions of this study, the growth kinetics and physicochemical properties of boron carbonitride layers are influenced by both the substrate temperature and rf power. Conditions are found for producing boron carbonitride films transparent in the UV through visible spectral region.