The peculiarity of interdiffusion and phase equilibrium has been studied for poly-m-phenyleneisophthalamide and poly-p-amidobenzimidazole systems during formation of a transitional layer in conditions of organoplastics. The investigation of this process has been based on the method of electron-probe X-ray spectral microanalysis. The effect of temperature, pressure and time of thermal treatment on dimensions of diffusional zones and kinetics of their formation was shown. The parameters of solubility and mutual diffusion of components were determined and phase diagrams were obtained.

Based on the tight-binding bond recursion method, the energetics parameters of ∑3[111] grain boundary in nickel are investigated. The theoretical results indicate that the boron enhances interatomic energy between the host atoms, and between impurity and nickel atoms. Calculations of the energy of the grain boundary segregation show that boron, nitrogen, and phosphorus have the tendency to segregate onto the grain boundary and segregation property of boron is stronger than that of nitrogen and phosphorus.

Based on Gauss’ principle of least constraint and Nosé-Hoover thermostat formulation, the numerical algorithms for molecular dynamics simulation are developed to investigate the properties of grain boundary in transition metals Fe and Ni at finite temperature. By the appropriate choice of heat bath parameter, a constant temperature version can be realized. A series of parameters are introduced to describe quantitatively the crystallographic characteristic and the distortion of structure unit. The results indicate the applicability of the calculation mode developed by us and reveal the feature of the atomic structure of grain boundary at finite temperature.

Cavitation effects have long been considered to be undesirable phenomena that resulted in the damage and failure of metallic components. In the present work, we establish that, in fact, controlled applications of ultrasonic cavitation phenomena can be used to enhance the surface properties of both ceramics and metals. Polished (100) surfaces of single-crystal MgO and single crystals of 70%Fe-15%Ni-15%Cr (stainless-steel) were subjected to ultrasonically induced cavitation by exposure to 20 kHz excitations (at ∼ 100 W/cm2) in isopropanol. Knoop micro-indentation hardness measurements on untreated and ultrasonically treated areas of the surfaces revealed a hardening that increased with the duration of the ultrasonic treatment up to a saturation level. Relative increases in the surface hardness of up to 30% in the case of MgO and ∼250% in the case of Fe-Ni-Cr were obtained. It was found that the rate of hardening was not uniform over the surface but was more rapid on those portions of the surface that were directly under the edge of the ultrasonically vibrating horn tip.

The deposition of glass films on thin ceramic substrates is a novel method for investigation of the initial stages of liquid infiltration into the grain boundaries of these materials. By maintaining electron transparency at all stages of the experiment, the transmission electron microscope (TEM) can be used to characterize individual grain boundaries before and after penetration by a liquid. The method has been tested for the MgO and AI2O3 systems, which have extensively studied experimental counterparts in which the corresponding bulk materials are infiltrated by a siliceous liquid.

Results of detailed study on interlaminar fracture toughness of hybrid aramid-epoxy/aluminum laminate composites are presented. A fracture mechanics approach has been adopted and Mode-I, Mode-II tests for a wide range of loading rates have been used. Hybrid composite failure loci has been studied using SEM technique. Results were analyzed from the point of view of metal substrate/aramid fibre surface free energy effect on near interfacial (in the boundary layers) microstructure and fracture toughness of elastomer modified epoxy resins. It has been shown, that toughened epoxy resin morphology (rubber particles size and volume content) and, as a result, fracture resistance of the boundary layers were strongly dependent upon the adsorption processes, that could take place during adhesion contact formation and curing. To increase interfacial fracture toughness of hybrid composites due to the improvement of near interfacial resin microstructure and boundary layer fracture resistance, as for aluminum-epoxy and for aramid-epoxy failure loci, metal sheets/aramid fibres surface properties and interfacial residual thermal stresses should be optimized. The last result has been achieved by means of si lane primer treatment of aluminum laminates and tensile loading of cured composite.

There is a growing demand for advanced composites which can maintain their structural strength in high-temperature environments, particularly for aerospace applications. The use of graphite fiber/nickel metal matrix composites would be desirable if the deterioration of mechanical properties resulting from interdiffusion of carbon and nickel at temperatures in excess of 600°C could be avoided. The present research concerns an electrodeposited cobalt alloy coating containing 5-10.5 at-% tungsten, which was designed to serve as a diffusion barrier between graphite fibers and a nickel matrix. The resulting graphite/Co-W/Ni composite was tested under various time/temperature conditions, and the coating was shown to inhibit diffusion for up to 24 hr at 800°C. Annealed and unannealed coated fibers were analyzed by x-ray diffraction and by transmission electron microscopy The as-deposited coating was found to contain both h.c.p. and f.c.c. cobalt, whereas only f.c.c. was observed after annealing at 1100°C for 1.5 hours. WC was found at the coating/fiber interface.

Microscratch testing of thin films has mainly been done with a conical tip. In the wedge scratch technique introduced in this paper, thin film fine lines are scratched by a wedge-shaped diamond tip until a spallation occurs. A near plane strain situation arises, and finite element method (FEM) analysis is applied for more accurate evaluation of the work of adhesion. The material system used to demonstrate the micro-wedge scratch technique is rf-sputtered tungsten on thermally grown SiO2. When scratching a long line, delamination occurs by two mechanisms. At loads above 8-9mN/µm (normal load per unit line width), tensile stresses behind the indenter tip cause the tungsten to crack, and the thin film subsequently curls up. At loads above 1lmN/µm, high shear stresses in front of the indenter cause delamination of the tungsten at the interface. This latter event is modeled by FEM using a bimaterial fracture mechanics approach to obtain a practical work of adhesion value.

The diffusion of silicon into GaAs was investigated in this work. Shallow silicon carrier profile with doping levels in excess of 1018 cm−3 were obtained in GaAs by rapid thermal oxidation (RTO) of Si cap film in pure O2 with pressure 2 torr at 800 ∼ 900 ° C. SIMS revealed the presence of various degrees of interdiffusion in / near the interface between Si and GaAs as being a function of oxidation temperature and cap thickness. Ga and As atoms were observed in Si film. Silicon and oxygen were also found in the GaAs wafer. The silicon and arsenic atoms were segregated in / near the interface. The Si atoms could be driven further into GaAs by additional rapid thermal annealing (RTA) process. The above phenomena were confirmed by the electrical measurements taken on sheet resistance, doped dose, and mobility. The TaSix / GaAs Schottky barriers were also fabricated. The ideality factor, Schottky barrier height, and breakdown voltage are the functions of the doping level. This behavior could be accounted for by the theory of tunnel effect of Schottky barrier.

Degradation of 430 nra thick SiO2 layers in Si/SiO2/Si structures which results from high temperature annealing (1320°C) has been studied using electron spin resonance, infra-red absorption spectroscopy and refractive index measurements. Large numbers of oxygen-vacancies are found in a region ≤ 100 nm from each Si/SiO2 interface. Two types of paramagnetic defects are observed following γ or X-irradiation or hole injection. The 1106 cm−l infra-red absorption associated with O interstitials in the Si substrate is found to increase with annealing time. The infra-red and spin resonance observations can be explained qualitatively and quantitatively in terms of a model in which oxygen atoms are gettered from the oxide into the under or overlying Si, the driving force being the increased O solubility limit associated with the anneal temperature.

The deposition and processing of thin films, such as barrier metals and anti-reflective coatings, can be enhanced using the information provided by various surface analysis techniques. We will show the application of x-ray photoelectron spectroscopy(XPS) to the production of Ti and TiN films suitable for use in ULSI CMOS integrated circuits. XPS can separate Ti and N photoelectron peaks and detect low (1.0-5.0 atomic%) contamination levels while providing surface and interface chemical state information. In this paper we will show that a) the effect of TiN deposition on subsequent Ti film quality from the same Ti target was determined to be minimal, b) the relation of anneal temperature to the extent of SiO2 reduction by Ti metal was characterized on SiO2/Ti/TiN structures for temperatures from 600°C to 800°C, and c) the absorption of O into TiN films from ambient air was detected and confirmed.

High purity bicrystals of MgO have been grown using chemical vapor transport for the purpose of studying oxygen grain boundary diffusion. Preliminary data indicate preferential diffusion of oxygen along ∑ 13 symmetric tilt boundaries. The measured grain boundary diffusivities were approximately 4 orders of magnitude higher than the corresponding bulk values. The activation energies for bulk and grain boundary diffusion were found to be equal to within experimental error, (≈3.9eV)

Ultrathin rapid thermal oxides have been formed in oxygen with varying levels of nitrogen incorporated into the oxidation ambient. Metal-oxide-semiconductor capacitors and MOSFET devices were subsequently fabricated and tested. Device reliability was degraded by the addition of nitrogen into the oxidation ambient. Time-independent catastrophic breakdown measurements showed a large increase in the number of extrinsic breakdowns in devices formed in higher levels of nitrogen. Device performance was measured by interface trap density, subthreshold slope, channel mobility and threshold voltage. A small increase in the interface trap density was observed for increasing levels of nitrogen in the oxidation ambient. However, no trends were observed for MOSFET devices in terms of subthreshold slope, channel mobility or current drive. No improvement in the interface state generation rate due to nitrogen incorporation in the oxidation ambient was observed in this study. X-ray photoelectron spectroscopy detected no nitrogen in the oxides indicating less than 1% nitrogen incorporation.

Scanning tunneling microscopy has been used to study the initial stage of Cu growth on SrTi03(001) surfaces. Our STM results show that Cu grows initially into 3-D island-like structures. Two different morphologies were observed. In some areas loosely bound individual Cu islands appear preferentially attached to step edges. The islands were frequently relocated by the STM tip during the scanning as a result of tip-surface interaction. Other areas have higher densities of Cu islands that exhibit a narrow size distribution with an average diameter of 70 Å and are homogeneously distributed on those areas. The driving force for the morphological evolution of Cu on the SrTiO3(001) surface is discussed in terms of surface free energy and interfacial interaction of metal on transition metal oxide surfaces.

The application of ferroelectrics such as SrTiO3 or PbZrxTi(1−x)O3 to the insulator of DRAM cell capacitors has been extensively studied. The bottom electrode Pt / Ti for these ferroelectrics needs to be thermally stable because of the crystallization process of ferroelectrics. By varying the annealing temperature from 400°Cto 800°C, we examined the annealing effects to the electrode Pt / Ti by SEM, TEM and in-situ XRD.

In this paper, we report the development of surface smoothing process for YB2CU3O7. x (YBCO) films. The SrTi03/YBCO interface characteristics were investigated as functions of polishing agent and polishing time. It was found that the 7% HF solution gave the best results both in structural and electrical properties. The leakage current through the SrTiÛ3 film grown on polished YBCO was reduced to about 3 orders of magnitude. The dielectric constant was also increased from 110 to over 300. The superconducting properties of the YBCO bottom layer degraded insignificantly after undertaking the surface smoothing process and the overlayer growth of STO. This surface smoothing process without post treatment is suitable for subsequent growth of epitaxial STO films and the fabrication of MCM’s.

Methods for characterizing the interface of conductive polymer/high-Tc superconductor sandwich structures are reported. Electrochemical procedures, such as cyclic voltammetry and chronoamperometry, are utilized to deposit conductive polymers directly onto bulk ceramic and thin film samples of YBa2Cu3O7-δ. Moreover, similar methods are utilized to cycle the polymer structures between their neutral (non-conductive) and oxidized (conductive) forms. Through changes in the polymer doping level, the superconducting properties of the high-Tc component can be modulated in a controllable and reproducible fashion. This paper focuses on an analysis of conductive polymer/superconductor interface phenomena as explored by electrochemical, resistivity vs. temperature and contact resistance measurements.

We discuss the development of interaction potentials which explicitly allow for charge transfer in metallic oxides. The charge transfer is calculated self-consistently using a charge equilibration approach, which allows the amount of charge transferred to respond to the electrostatic environment. We model the metal-metal, metal-oxygen, and oxygen-oxygen interactions with Rydberg function pair potentials. By fitting the Rydberg potential parameters to the elastic and structural constants of the material, we arrive at an efficient model for the simulation of metallic oxides. We demonstrate the applicability of the model by describing some preliminary results on the rutile phase of titanium dioxide.

We study possible morphologies of epitaxial films atop attractive substrates appearing as a result of competition of misfit stresses, van der Waals forces and surface energy. Corresponding formula for the critical thickness of the dislocation-free Stranski-Krastanov pattern is established for the isotropic deformable films and substrates. If the film thickness exceeds the critical magnitude the layer-by-layer pattern switches to islanding. At the first stage the islands have a shape of striae (i.e. long parallel trenches with periodic spacing). We discuss also i)the circumstances in which surface morphology of the film corresponds to a two-dimensional superlattice of islands rather than a one dimensional lattice of striae and ii)the influence of a buffer inter-layer.

Titanium aluminide alloys with compositions slightly on the Ti-rich side of stoichiometry consist of the intermetallic phases α2 (Ti3Al) and γ(TiAl). The two phases form a lamellar microstructure with various types of coherent and semicoherent interfaces. The lattice mismatch occurring at the semicoherent interfaces is largely accommodated by networks of interfacial dislocations. Nevertheless, a significant homogeneous straining seems to remain at these interfaces, resulting in long-range residual stresses. The present paper reports an electron microscope study of the correlation between the misfit strain of adjacent lamellae and the atomic structure of the interfaces. The residual coherency stresses were determined by analyzing the curvature of dislocation loops which were emitted from the network of the interfacial dislocations. The estimated stresses are close to the shear stresses applied during macroscopic deformation experiments. The effects of these stresses on the deformation behaviour of the material are discussed.