Two-phase Films Research Articles

Electrical and structural studies of AgSbSe2 thin films

Abstract Bulk AgSbSe2 was prepared by melting the constituent elements in stoichiometric proportions. The ternary composition thus obtained was found to possess an NaCl-type structure. X-ray diffraction and electron microscopy techniques were used to obtain insight into the structural information of the sample. AgSbSe2 films were prepared by thermal evaporation under vacuum (10−5 Torr) on clean glass substrates. The room temperature deposited films were amorphous in nature and an amorphous-to-crystalline transition could be obtained by thermal annealing at 423 K. The degree of crystallinity increased with increasing temperature and film thickness. When thick films of this composition were evaporated thermally in vacuum two-phase films with AgSbSe2 as a major phase were formed. The effect of thermal annealing was studied using electron microscopy diffraction. The electrical resistivity, the carrier concentration and the temperature coefficient of resistance of AgSbSe2 deposited onto glass substrates have been studied as a function of thickness.

Misfit dislocations and other defects in thin films

The methods and the results of calculations of the elastic properties of misfit and lattice dislocations and disclinations in thin films are considered. For one-phase films the following problems are solved: a straight edge dislocation perpendicular to the film surfaces; wedge disclinations parallel or perpendicular to the surfaces. In the case of a film on a substrate, the critical thickness for the appearance of misfit dislocations is determined in the continuum model. For multilayer films (superlattices) the effect of a reduction in the grown-in dislocation density is analysed. The behaviour of dislocations in two-phase films is also briefly reviewed.

The structure and magnetic properties of two-phase PtMnSbMnSb thin films

The process of solid state phase formation by thermal annealing of multilayered films consisting of two kinds of unit lamella, Pt/Mn/Sb and Mn/Sb, was investigated by means of X-ray diffraction and transmission electron microscopy. The magnetization loops of the films were measured at room temperature by using a vibrating-sample magnetometer. Films consisting of the two phases PtMnSb and MnSb were successively produced. the relative amount of the PtMnSb and MnSb phases was considerably affected by the average composition of the multilayered films and the annealing conditions. The initial stacking pattern had a significant effect on the preferred orientation of the MnSb phase: the c axis of MnSb was preferentially orientated normal to the film surface in some annealed samples. Although films with perpendicular magnetic anisotropy could not be obtained, the part of the samples in which the c axis preferred orientation of MnSb was developed exhibited the presence of a component of perpendicular magnetization.

Growth of semiconducting ternary thin films of AgSbTe 2

Bulk AgSbTe 2 was prepared by melting the constituent elements in stoichiometric proportions. The ternary composition thus obtained was found to possess an NaCl-type structure. This composition when evaporated thermally in vacuum onto sodium chloride cleavage surfaces was found to lead to the formation of two-phase films with AgSbTe 2 as the major phase. However, monophase AgSbTe 2 films could be obtained by suitably adjusting the starting material composition. The effects of thermal annealing and condensation temperature on the stability of the single phase were studied through electron diffraction.

Preparation and magnetic properties of two-phase PtMnSbMn2Sb thin films

Abstract Thin films consisting of the two phases of PtMnSb and Mn2Sb were prepared by thermal annealing of ion-beam-sputtered Pt/Mn/Sb multilayers. The preferred orientation of the constituting phases was greatly affected by the initial stacking pattern of the multilayers. The magnetic measurements revealed the perpendicular magnetic anisotropy in the samples with a strong c- axis preferred orientation of the Mn2Sb phase.

Properties of two-phase cadmium stannate thin films

Thin films of cadmium stannate were prepared from a Cd 2SnO 4 target by r.f. sputtering. Optical and electrical properties were studied as functions of film thickness and related to changes in composition and structure; in particular, the presence of both amorphous and crystalline phases within the same film was demonstrated for the first time. The surface composition of the films, in contrast to the bulk composition, was shown to be significantly affected by heat treatment, with clear implications for the use of cadmium stannate as a transparent conductor in electronic devices. It is concluded that failure to control adequately parameters such as deposition temperature can lead to non-uniformity of structure and properties within a single run and variability from one run to another.

Triple-point wetting of H2 films adsorbed on silver.

The wetting behavior of ${\mathrm{H}}_{2}$ films adsorbed on silver was studied with a quartz-crystal microbalance. Below the triple-point temperature ${T}_{t}$, incomplete-wetting films are observed, while above it the liquid films completely wet the substrate. Within the experimental resolution the wetting transition occurs at ${T}_{t}$. The maximum frequency change at saturation (which corresponds to the film thickness at saturation) increases as the temperature approaches ${T}_{t}$, obeying a power law of the form \ensuremath{\Delta}${f}_{0}$\ensuremath{\propto}${t}^{\mathrm{\ensuremath{-}}1/n}$, with n=3.28\ifmmode\pm\else\textpm\fi{}0.3 and t=(${T}_{t}$-T)/${T}_{t}$. The shape of the isotherms suggests the presence of two-phase films above and below the triple point.

Structure and properties of TiN coatings

During the last few years there has been increasing interest in TiN thin films deposited by various physical vapour deposition methods. Since the films are grown by various techniques and using different process parameters the variation in the actual growth conditions is considerable. This gives rise to a large scatter in the microstructures and hence also in the properties of the films. In this paper reported microstructures of thin films of TiN are reviewed and are also correlated to physical properties such as the electrical resistivity and the hardness of the films. For example, one important microstructural feature is voids located in the grain boundaries. Such voids result in low hardness values and high resistivities. The origin of the various microstructures that are obtained is also discussed in terms of the growth conditions used. The voids mentioned above can, for example, occur because of deviation from stoichiometry, too low a substrate temperature or impurities in the films, but also because of substrate-induced growth effects specially if multiphase substrates such as high speed steels are used. In addition to single-phase TiN films, two-phase or multiphase films containing the phase Ti2N are also discussed. In many cases such films show extremely high film hardnesses. However, it is shown that the high hardnesses are mainly caused by the specific microstructures that can develop rather than by the Ti2N phase itself.

Growth of thin films of Cd xHg 1− xTe solid solutions by cathodic sputtering in a mercury vapour plasma

A study of the formation of films of Cd x Hg 1− x Te solid solutions by sputtering in a mercury vapour plasma was carried out. The condensation rate and the condensed material composition were investigated experimentally as functions of the main sputtering parameters, namely the sputtering pressure, the substrate temperature, the sputtered fluxes, the target voltage and the bias voltage. The role of the mercury vapour pressure was determined, as well as the conditions of formation of single-phase or two-phase films. The study of condensed fluxes and condensation coefficients of cadmium and tellerium atoms contributed to the understanding of the growth process.

Reactively evaporated photoconductive PbO: Phase transformations induced by water vapor

Lead oxide films about 45 μm thick and 80% dense were grown on water-cooled anodized aluminum substrates by the reactive evaporation of pure lead in a low pressure oxygen atmosphere. X-ray diffraction analysis showed that the as-deposited films were a mixture of free lead and orthorhombic β-PbO, the high temperature polymorph. The exposure of these two-phase films to room temperature air (or oxygen) with high partial pressures of water vapor greatly enhanced the kinetics of oxidation as well as the transformation of orthorhombic PbO to tetragonal PbO, the low temperature polymorph. The films were converted to essentially pure tetragonal PbO by a 175 °C anneal in air followed by a 435 °C anneal in nitrogen. With the air anneal only, photoelectronic characteristics of the films were highly variable and non-reproducible. Improved photoresponse and reduced sample-to-sample variation were obtained after the nitrogen anneal. Doubly annealed films exhibited room temperature dark resistivities as high as 2 × 10 14 ω cm and photocurrent quantum efficiencies approaching unity at a field strength of 2 × 10 4 V cm −1 and when illuminated with 45 μW cm −2 of 608 nm (volume absorbed) light. The concentrations of basic lead carbonates, hydrocerussite 2PbCO 3·Pb(OH) 2 and plumbonacrite 6PbCO 3·3Pb(OH) 2·PbO, detected in the films at every stage of processing, were decreased by the high temperature nitrogen anneal.

Negative magnetoresistance of two-phase polycrystalline p-type InSb films

Negative magnetoresistance of two-phase polycrystalline p-type InSb films

Thin film optical properties in relation to film structure

The optical properties of solids may be strongly influenced by their crystalline, morphological and compositional structure. In this paper we review the effect of quench condensation on the optical properties of metal films. A few pure metals may be made amorphous by quench condensation; however, most metal films are microcrystalline. We review the spectra of the amorphous metals and give an account of the additional absorption found in many microcrystalline films. This effect is similar to effects found in metal films with rough surfaces, in discontinuous thin films and in two-phase metal-insulator films and is caused by the excitation of surface plasmons propagating along grain boundaries. Theoretical calculations which support this explanation will be presented. A brief account of the effect of thermal disorder on the optical response is included in the discussion, and we also give examples of the effect of allotropic phase transformations on the optical properties of selected solids.

An internal calibration technique for pseudobinary systems by auger electron spectroscopy

An internal calibration technique has been developed for the quantitative analysis of pseudobinary systems by means of Auger electron spectroscopy without the need for stan-dards of known composition. This technique has been used for analyzing PbO-In2O3 two-phase films and A1N-A12 O3 , AlAs-GaAs, and GaP-InP solid solutions. The technique is applicable to systems of the type (ACm) (BCn)1-x if the Auger intensities measured for elemens A, B, and C are given by the linear relationships I = xIA **, IB = (l-x)IB *, and IC = xIC ** + (l-x)IC C * where IA ** and IC ** are the inten-sities for pure ACm and IB * and I* are the intensities for pure BCn . To determine whether this criterion is satisfied, a series of Auger measurements is made on regions of dif-ferent composition within a single specimen (e.g., on speci-mens in which a concentration variation exists across the surface or surfaces exposed by repeated sputter-etching of a sample with an in-depth composition gradient), and plots of IA vs IB and IC/IB vs IA/IB are made. If these plots are linear over tne range of compositions investigated, it is assumed that the above linear relationships are valid over the whole range of the pseudobinary system. It is then possible to construct linear calibration plots of IA, IB , and IC vs x for the whole composition range.

472. Gauss effect in two-phase InSb-In films

472. Gauss effect in two-phase InSb-In films

Hard magnetic two-phase Co-Cu thin films

The magnetic properties of sputtered films of 25 Co-75 Cu and 50 Co-50 Cu before and after annealing were investigated. In the as-sputtered state the films exhibit the structure of a metastable fcc solid solution. Annealing at 500 to 700°C causes decomposition into two phases, Cu and fcc 89 Co-11 Cu. The decomposition supposedly occurs by heterogeneous nucleation at the grain boundaries, and growth by grain boundary diffusion. The 89 Co-11 Cu phase exists in the form of small particles with magnetic single domain behavior. The films have coercivities up to 280 Oe. Squareness ratios between 0.7 and 0.9 were found. No strain sensitivity of the magnetic properties could be detected. This material is regarded to be suitable for magnetic recording.

Hard magnetic two-phase Co-Cu thin films

Hard magnetic two-phase Co-Cu thin films

InSb film raster pattern magnetoresistors

The transverse magnetoresistance of InSb film magnetoresistors with a metallic line raster pattern was determined for identical line and space width of 127, 72.4 and 42.4 μm respectively. The fair agreement between calculated and experimental data suggests that the theoretically derived geometry dependence of ( ΔR R 0 ) is applicable. The magnetoresistance of the raster pattern magnetoresistors, in a field of 10 koe, is shown to be considerably greater than that of two-phase dendritic InSb films.