Ion-plasma Sputtering Research Articles

Growth features and spectroscopic structure investigations of nanoprofiled AlN films formed on misoriented GaAs substrates

Nanostructured aluminum-nitride films are formed by reactive ion-plasma sputtering onto GaAs substrates with different orientations. The properties of the films are studied via structural analysis, atomic force microscopy, and infrared and visible–ultraviolet spectroscopy. The aluminum-nitride films can have a refractive index in the range of 1.6–4.0 at a wavelength of ~250 nm and an optical band gap of ~5 eV. It is shown that the morphology, surface composition, and optical characteristics of AlN/GaAs heterophase systems can be controlled using misoriented GaAs substrates.

Features of AlN film grown by ion-plasma sputtering

The work under consideration presents research of structure, composition and optical properties of aluminium nitride thin films grown by reactive ion plasma sputtering. Aluminium nitride films are shown to contain amorphous and polycrystalline phases. Amorphous phase presence influences on refraction and absorption indexes. Conditions of polycrystalline films with primary (dedicated) orientation synthesis are revealed.

Structure and phase composition of deposited tantalum–carbon films

Ion plasma sputtering and the subsequent codeposition of ultrafine tantalum and carbon particles were used to prepare coatings with 4.6–71.5 at % C. Structural studies of the coatings showed the existence of carbon solid solutions in β Ta at carbon contents to 4.6 at %, carbon solid solutions in α Ta at carbon contents of 4.6–10.3 at %, and direct synthesis of TaC at carbon contents of 44.7–71.5 at %. During heat treatments to 700°C, the substantial concentration widening of regions of the existence of Ta2C and TaC was found. The lattice parameters of hexagonal Ta2C and fcc TaC carbides were determined for composition ranges of the existence of phases during heating to 700°C. Upon heating above 600°C, the progressive transition of quasiamorphous Ta2C carbide into the crystalline Ta2C carbide was found to take place. The possibility of applying the direct synthesis of TaC carbide in engineering was noted.

Dispersion Properties of (Y0.06GA0.94)2O3 Thin Films

We have studied the refractive index dispersion in (Y0.06Ga0.94)2O3 thin films obtained by high-frequency ion plasma sputtering. We show that the films are formed with mixed orientation, and the maxima of the diffraction patterns correspond to the monoclinic crystal structure of β-Ga2O3. We have established that as for β-Ga2O3 films, we observe anomalous dispersion in the near UV region for (Y0.06Ga0.94)2O3 films annealed in hydrogen, while we observe normal dispersion for films annealed in oxygen or argon. For the studied films with normal dispersion, we compare two single-oscillator approximation models, and we fi nd the parameters of the approximation, the dispersion energy, the chemical bond ionicity, the coordination number, the static refractive index, the characteristic wavelength for UV absorption, and the average oscillator absorption energy. We established that the static refractive index in the studied films increases as the number of oxygen vacancies increases, and that it is inversely proportional to the average oscillator absorption energy.

Magnetic and magnetoresistive properties of Al2O3–Sr2FeMoO6–δ–Al2O3 nanoheterostructures

A method has been developed for fabricating nanoporous matrices based on anodic aluminum oxide for the deposition of ferromagnetic nanoparticles in them. The modes of deposition of strontium ferromolybdate thin films prepared by the ion-plasma method have been worked out, and the magnetic and magnetoresistive properties, structure, and composition of the films have been investigated. It has been revealed that the microstructure and properties of the strontium ferromolybdate films deposited by ionplasma sputtering depend on the deposition rate and the temperature of the substrate. Based on the measurement of the electrical resistivity of nanoheterostructures in a magnetic field, it has been found that the magnetoresistance reaches 14% at T = 15 K and B = 8 T, which is due to the manifestation of tunneling magnetoresistance.

Microstructure and magnetic properties of [formula omitted] thin films

This paper surveys structure and magnetic properties of the thin films with thicknesses of 30, 70, 100 and 200nm, prepared by high-frequency ion-plasma sputtering of Fe72.5Si14.2B8.7Nb2Mo1.5Cu1.1 target onto monocrystalline Si substrates. As-deposited films exhibited the roentgen-amorphous state and in-plane induced magnetic anisotropy. Their crystallization and drastic growth of the grains up to 40nm at 460°C were revealed and examined by X-ray diffraction methods. Among the measured magnetic properties of the films, the magnetic anisotropy and coercivity were stressed. Their changes with the annealing temperature and film thickness were discussed. The influence of the surface roughness on the coercivity was also investigated with atomic force microscopy.

Visible Raman spectroscopy of carbon films synthesized by ion-plasma sputtering of graphite

Abstract

Technology of Porous Tantalum Production

Ion-plasma sputtering and codeposition of ultrafine Ta and Cd particles on a moving substrate were used to prepare the solid solutions, in particular, the alloys with up to 66.2 at.% Cd in the form of coatings. In vacuum heat treatment cadmium evaporates at 700&degC from cadmium based solid solutions resulting in formation of a porous tantalum with a highly developed surface. The prepared tantalum-based materials assume the technological application of the investigation results.

Composite materials obtained by the ion–plasma sputtering of metal compound coatings on polymer films

In this article, the principle and examples composite materials obtained by deposition of metal compound coatings on polymer film substrates by the ion–plasma sputtering method are presented. A synergistic effect is to obtain the materials with structural properties of the polymer substrate and the surface properties of the metal deposited coatings. The technology of sputtering of TiN coatings of various thicknesses on polyethylene terephthalate films is discussed. The obtained composites are characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), and scanning tunneling microscopy (STM) is shown. The examples of application of this method, such as receiving nanocomposite track membranes and flexible transparent electrodes, are considered.

Properties of AlN films deposited by reactive ion-plasma sputtering

The properties of SiO2, Al2O3, and AlN dielectric coatings deposited by reactive ion-plasma sputtering are studied. The refractive indices of the dielectric coatings are determined by optical ellipsometry. It is shown that aluminum nitride is the optimal material for achieving maximum illumination of the output mirror of a semiconductor laser. A crystalline phase with a hexagonal atomic lattice and oxygen content of up to 10 at % is found by transmission electron microscopy in the aluminum-nitride films. It is found that a decrease in the concentration of residual oxygen in the chamber of the reactive ion-plasma sputtering installation makes it possible to eliminate the appearance of vertical pores in the bulk of the aluminum-nitride film.

Study of the optical and photoluminescence properties of nanostructured zinc oxide films obtained by the ion–plasma method

This paper presents the results of a study of the structural, optical, and photoluminescence properties of nanostructured zinc oxide films created by the method of ion–plasma sputtering of a metallic target at various gas pressures. It is shown that such zinc oxide films possess optical and photoluminescence properties close to those of single-crystal zinc oxide and can be used as a material for creating thin-film acoustooptic devices that operate on surface acoustic waves or for the receptor areas of UV photodetectors.

Cadmium telluride in tellurium—cadmium films consisting of ultradispersed particles

Solid solutions of tellurium in cadmium, cadmium in tellurium, and cadmium in cadmium telluride synthesized during sputtering are formed for the first time by ion-plasma sputtering and the codeposition of ultradispersed Te and Cd particle fluxes onto substrates moving with respect to the fluxes. This fact supports thermofluctuation melting and coalescence of small particles. The lattice parameter of cadmium telluride, which coexists with an amorphous solid solution of tellurium in cadmium in a coating, is smaller than the tabulated value and reaches it when the cadmium concentration in a coating increases to 70 at %. The lattice parameter of the fcc lattice of cadmium telluride increases with the cadmium concentration in a coating according to the linear relation a = 0.0002CCd + 0.6346 nm (where CCd is the cadmium concentration in the coating, at %), which is likely to indicate a certain broadening of the homogeneity area. The estimation of the particle size shows that the cadmium telluride grain size is 10–15 nm, which implies that the coatings are nanocrystalline. The absorption and transmission spectra of the tellurium—cadmium films at the fundamental absorption edge demonstrate that their energy gaps are larger than that of stoichiometric CdTe, which can be explained by the experimental conditions of crystal structure formation.

Formation of porous α tantalum in films

Ta—Cd alloys in the form of coatings with up to 66.2 at % Cd are fabricated for the first time by ion-plasma sputtering and the subsequent codeposition of ultradispersed Ta and Cd particles. At a concentration higher than 44.0 at % Cd, tetragonal β-Ta transforms into bcc α-Ta. Beginning from 74.4 at %, cadmium forms its hexagonal lattice and tantalum in the coatings is represented by an amorphous phase. During vacuum heat treatment at 700–750°C, cadmium evaporates from the binary tantalum—cadmium system containing more than 74.4 at % Cd, and a porous tantalum coating with a well-developed surface forms. Tantalum in the coating is represented by various flakelike crystallites, and tantalum in the near-surface layer mainly has a globular shape. A comparison of the specific surface areas of a tantalum film and the porous tantalum coating, which is performed by the BET method, demonstrates that the specific surface area increases by 277.5 m2/g Ta. Our results can be applied to other binary systems having similar properties.

Investigations of nanodimensional Al2O3 films deposited by ion-plasma sputtering onto porous silicon

The purpose of this study is the deposition of nanodimensional Al2O3 films on the surface of nanoporous silicon and also fundamental investigations of the structural, optical, and morphological properties of these materials. Analyzing the results obtained here, it is possible to state that ultrathin nanostructured Al2O3 films can be obtained in the form of threads oriented in one direction and located at a distance of 300–500 nm from each other using ion-plasma sputtering on a layer of porous silicon. Such a mechanism of aluminum-oxide growth is conditioned by the crystallographic orientation of the initial single-crystalline silicon wafer used to fabricate the porous layer. The results of optical spectroscopy show that the Al2O3/por-Si/Si(111) heterophase structure perfectly transmits electromagnetic radiation in the range of 190–900 nm. The maximum in the dispersion of the refractive index obtained for the Al2O3 film grown on por-Si coincides with the optical-absorption edge for aluminum oxide and is located in the region of ~5.60 eV. This fact is confirmed by the results of calculations of the optical-absorption spectrum of the Al2O3/por-Si/Si(lll) heterophase structure. The Al2O3 films formed on the heterophase-structure surface in the form of nanodimensional structured threads can serve as channels of optical conduction and can be rather efficiently introduced into conventional technologies, which are of great importance in microelectronics and optoelectronics.

Structure and phase composition of films formed by ultradispersed particles of iron and carbon

Ion-plasma sputtering and the codeposition of ultradispersed iron and carbon particles are used to create their solid solutions containing 17.6 at % carbon. Solid-solution alloys formed immediately during deposition confirm the theory of the thermal-fluctuation melting of small particles. Coating deposition is accompanied by the generation of an X-ray amorphous carbide phase, the amount of which correlates with the initial C concentration in the sample. The coating possesses an amorphous structure if the carbon content is 23.9 at %. By means of nuclear gamma-resonance spectroscopy, it is found that the magnetic moments of iron atoms are anisotropically oriented due to the formed textured coatings. The deviation of crystallite orientations from the average direction of the texture axis depends on the degree of carbonization. Pearlite eutectic (α-Fe(C) + Fe3C) arises from the amorphous phase without the formation of intermediate carbides at a temperature of 500°C. The relative cementite content correlates with the amount of carbon embedded into the coating.

Effect of Preparation Conditions on the Fundamental Absorption Edge of Y2O3 Thin Films

The fundamental absorption edge of Y2O3 thin fi lms obtained by discrete evaporation and high-frequency (HF) onplasma sputtering in various atmospheres was studied using optical spectroscopy. It was ascertained that the optical bandgap Eg increased from 5.65 eV for Y2O3 fi lms obtained by discrete evaporation to 5.77 eV for fi lms obtained by HF sputtering in Ar to 5.90 eV for fi lms obtained by HF sputtering in O2. The effective reduced mass of free charge carriers was estimated. It was found that the concentration of free charge carriers in Y2O3 fi lms obtained by ionplasma sputtering in Ar with 50% O2 was N = 1.34·1017 cm–3 whereas sputtering in 100% O2 gave N = 1.38·1018 cm–3, which was typical of degenerate semiconductors. It was shown that the shift of the fundamental absorption edge in Y2O3 thin fi lms after addition of O2 to the sputtering atmosphere was most likely caused by the Burstein–Moss effect.

Ultrathin nano-sized Al2O3 strips on the surface of por-Si

The objective of this paper is to obtain nano-sized Al2O3 strips on the surface of nanoporous silicon surface as well as fundamental investigations of structural, optical and morphological properties of the materials.While analysing the results, we were able to prove for the first time that the use of ion plasma sputtering allows one to obtain ultrathin nanostructured Al2O3 films as unidirectional fibres arranged by 300–500nm away from one another on a porous silicon layer. Such mechanism of the growth of aluminium oxide strips is stipulated by the morphology of porous silicon layer obtained as a result of etching of the virgin silicon plate; that in turn determines distinctions in the morphology of ultra-thin Al2O3 film.The results of optical spectroscopy shows that the Al2O3 nano-sized strips of the heterophase structure of Al2O3/por-Si/Si(111) is good at transmitting electromagnetic radiation of 190–900nm. It is shown that the intensity of photoluminescence excited by the heterophase structure Al2O3/por-Si/Si(111) is by 30% higher than that excited by the film of the porous layer.The analysis of dispersion of refractive index in the investigated systems showed that its values for the heterophase structure Al2O3/por-Si/Si(111) in the entire range of the wavelengths of the deflection is considerably higher than that those ones of Al2O3 grown under similar conditions using single-crystalline silicon Si(111). In the wavelengths of 250–500nm the refractive index of the heterophase structure Al2O3/por-Si/Si(111) is similar to that one of por-Si used for growing of the heterophase structure.The observed maximum in the dispersion of the refractive index of Al2O3 nano-sized strips grown on por-Si is identical to the optical absorption edge of the aluminium oxide and is in the range of ~5.60eV. This is consistent with the results of calculations of the optical absorption spectrum for the heterophase structure Al2O3/por-Si/Si(111).The nano-sized structured strips of Al2O3 films on the surface of the heterophase structure can serve as optical transmission channels and are quite efficiently introduced into the standard practices, which is of significant importance for micro- and optoelectronics.

Plasma Metallization Coating and Its Adhesion to Microwave Transistor Substrate—Part 2: Experimental Study of 3-D Composite Coating

This paper reports an experimental study of the previously proposed mechanism of adhesion of a plasma metal coating to a ceramic substrate by an example of beryllium oxide. This adhesion mechanism is based on the increase in the concentration of structural defects (vacancies) and electron exchange interaction of a metal-oxide beryllium pair during the plasma thermal activation of the process. Given the brazing of ceramic products with hard solders in hydrogen, the coating composition for metallization is determined. The optimal temperature of reactive plasma metal coating for strong adhesion to the ceramic substrate is found. Methods to improve the technology of plasma vacuum metallization using ion-plasma magnetron sputtering and ion implantation are proposed. Recommendations for the deposition of 3-D composite coatings with maximum adhesion are given.

Study of the structural and optical properties of thin polycrystalline zinc oxide films obtained by the ion-plasma method

This paper presents the results of a study of thin polycrystalline films of zinc oxide, created using the new Elion technology—ion-plasma sputtering of a metallic target in the medium of a powerful gaseous oxidant. It is shown that the ion-plasma method can be used to synthesize thin polycrystalline films of zinc oxide with optical properties close to those of single-crystal zinc oxide. The optical properties of thin polycrystalline zinc oxide films synthesized by the ion-plasma method can be used as a light–sound guide of thin-film acoustooptic devices that operate on the basis of surface acoustic waves or UV photodetectors.

Structure and properties of Mg, Al, Ti oxide and nitride layers formed by ion-plasma sputtering

Structure and properties of Mg, Al, Ti oxide and nitride layers formed by ion-plasma sputtering