Conditions are established whereby step heights may be measured in the acid-washed and air-annealed MgO single-crystals currently employed as substrates for pulsed-laser-deposition. Preliminary data indicates that the steps are typically a few nanometers in height.

The morphology of Si3N4 deposited on Al2O3, BN, and SiC by low pressure chemical vapor deposition (LPCVD) was characterized as a function of deposition temperature. At 1200°C, faceted Si3N4 crystallites were deposited on SiC whereas Si3N4 deposited on the other substrates tended to be amorphous. With an increase in temperature to 1430°C, Si3N4 deposited on these substrates was polycrystalline. At this temperature, the microstructure of Si3N4 was not significantly influenced by the changes in substrate surface.

A novel processing technique has been developed to coat Al2O3 on Nb in an argon atmosphere with very low O2 content. It has been proposed1 that the low O2 content helped to increase the defect concentration in the ceramic phase resulting in an enhanced diffusion of Nb into Al2O3 at the metal-ceramic interface at a relatively low bonding temperature. A mathematical model has been developed1 to understand the effect of purified bonding atmosphere on interfacial diffusion. While diffraction studies in the transmission electron microscope revealed1 extensive amorphization at the metal-ceramic interface, EDX analysis showed1 that the interfacial amorphous phase has a very high concentration of O. Additionally, this phase is found to contain Al and Nb. The interfacial phase is formed due to the diffusion of Nb into the ceramic phase. The paradoxical phenomenon of O enrichment of the interfacial amorphous phase in a low O2 containing bonding atmosphere is due to the loss of gaseous oxides of Al from this phase. These oxides have relatively less proportion of O compared to Al2O3. Continuous loss of such oxides from the amorphous phase to the gaseous phase will, therefore, result in an O to Al ratio (in the amorphous phase) far exceeding that in Al2O3 (3:2).

Conformal growth is a confined epitaxial lateral overgrowth technique capable of yielding low dislocation density GaAs films on Si. This technique makes extensive use of selective epitaxy and crystal growth is confined by a dielectric cap as well as by the self-passivated Si surface itself.

In this paper, we have performed a detailed characterisation of the state of stress of the GaAs films in various configurations (after conformal growth and removal of the seed regions, and after the regrowth of an MBE layer) by photoluminescence measurements at 5K and X-ray diffraction experiments. Although the as-grown conformal films are found in the same state of stress than reference MOCVD GaAs epilayers on Si, we report a significant decrease of this stress after MBE regrowth on conformal films.

A model for diamond growth on stepped diamond (100)2×1 surfaces is proposed, involving adsorption and reaction of CH3 and H on a dimer-reconstructed surface. Surface rearrangments and the breaking of C-C dimer bonds by H and/or H2 are suggested to be important The energetics were estimated by molecular mechanics (MM3). Growth is concluded to occur predominantly by extension of dimer rows, yielding a smooth surface, due to steric and bond-strain constraints on the positions of precursor-addition reactions and the kinetic stability of type SB steps against etching.

Microstructures of polycrystalline diamond thin films deposited on silicon (100) substrates which were pretreated by (a) wet polishing, (b) dry polishing, (c) sonication and (d) acid etching, respectively, have been studied by scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HREM). The thin films were deposited by using a Hot Filament Assisted Chemical Vapor Deposition (HFCVD) technique, with a methane to hydrogen ratio of 0.5%. Atomic Force Microscopy (AFM) was used to characterize substrate surfaces after the different pretreatments. The wet and dry polishing produced substrates with scratch type of defects while the sonication and acid etching caused pit type of defects. Planar and cross-sectional SEM studies indicated that diamond films on the wet and dry polished surfaces were continuous and had a high density of nucleation sites while the films on the sonicated and acid etched surfaces were discontinuous in nature under the same deposition time (8 hours) and condition. Cross-sectional HREM studies did not reveal any intermediate layers such as SiC and amorphous carbon between the thin films and substrates. Tungsten carbide nano-sized crystals, however, were observed to be dispersed at the interface region. These particles were believed to be formed during carburizing a fresh tungsten filament and deposited on the substrate during initial stage of growth.

The initial stages of bias-enhanced chemical vapor deposition (CVD) of diamond were investigated in a microwave-plasma system. Samples were characterized with TEM and concurrent electron energy loss spectroscopy (EELS) to characterize chemical bonding in the deposited material. The results show that a thin amorphous carbon film is deposited during biasing, and that diamond nucleation occurs on this amorphous film. Isolated regions of crystalline SiC within the amorphous layer were also observed at longer bias times. These regions apparently form by a reaction between the amorphous carbon layer and the silicon substrate.

Diamond films were produced at a relatively low pressures (<1 Torr) by the ECR-PACVD method of gas mixtures containing CO (5%), H2 (95%) and traces of oxygen at substrate temperatures from ambient (no intentional heating) to 1050°C. Faceted surface morphologies were observed even at the lowest temperature of growth. The microstructure is dominated by octahedral crystals below 600°C, by cubic crystals at 800–900°C, and by multiply twined (111) crystals at temperatures higher than 950°C. The weak temperature dependence of the growth rate is consistent with hydrogen abstraction from the growing surface being the rate controlling step.

We report a set of CH4 pyrolysis experiments in a UHV system on diamond surfaces having varying degrees of surface roughness or perfection. Scanning electron microscopy (SEM), Auger electron spectroscopy (AES) and reflection high energy electron diffraction (RHEED) were used to examine the formation of graphite and the resulting surface morphologies. A (100) type Ha natural diamond having 3 sputtered craters on the surface was used as the substrate, sp2 carbon was formed preferentially on the structurally defective crater surfaces after ∼3×1010 L of CH4 exposure at 900°C, whereas essentially no sp2 carbon was found on the flat portions of the diamond surface. Similar experiments were also carried out on a polycrystalline CVD diamond film and sp2 carbon was formed on that surface afte ∼4×109 L of CH4 exposure at 900°C. These results indicate that structural defects on diamond surfaces are a crucial factor in the preferential nucleation of sp2 carbon during CH4 pyrolysis.

High quality, transparent diamond films with relatively large deposition areas have been obtained from oxyacetylene combustion flames at the atmospheric pressure using nozzle tilted at an angle φ) with respect to the Mo substrates. These films are studied using scanning electron microscopy, X-ray diffraction, and Raman spectroscopy. Experimental results show that the surface morphology and microstructure depend strongly on the processing parameters such as the gas mixture ratio of acetylene to oxygen, substrate temperature, and the nozzle angle φ. The uniformity of diamond films have been improved using this tilted combustion flame technique and some problems related with this approach are discussed.

Time-resolved reflection and transmission measurements during heating are coupled with transmission electron microscopy (TEM) to study the crystallization of amorphous 75nm Co49Si51 films. The reflection decreases and the transmission increases upon crystallization. Optical data are converted to a measure of the fraction crystallized, χ=χ(T,t). A Kissinger analysis gives an activation energy for crystallization of 1.1 eV. TEM analysis of films crystallized in-situ show they are principally CoSi2 with a small amount of CoSi2. These results are being used for kinetic modelling of crystallization of amorphous Co-silicide films for potential use in Si mosfet and bipolar technologies.

The correlation between the surface morphology and the lattice relaxation in strained SiGe/Si heteroepitaxy has been studied. It is found that the surface crosshateched pattern develops as the strained epilayer thickness increases. The effect of thermal annealing and boron dopant level has also been studied. The result suggests that the crosshatched morphology on the surface is constituted by surface slip steps of glissile dislocation motion in the strained epitaxial growth processing.

The equilibrium structure of a variety of Si1−xGex/Si heterostructures have been simulated by Molecular Dynamics, modeled by the Stillinger-Weber potential, to investigate the effect of strain on the surfaces of SiGe thin Alms. It was found that the strain in SiGe/Si(100) thin films was relaxed by the segregation of Ge to the surface. Rebonding of sub-surface atoms into dimers in the presence of a vacancy or cluster of vacancies above them was observed in the ensuing surface reconstruction. For SiGe/Si, the amount of “re-bonded missing dimers” in the top two layers increased with increasing Ge composition. But for Ge/Si(100), a V-shaped twinning defect was observed in the Ge thin film. To further investigate the effect of strain on surface reconstruction, bulk Si and Ge structures were also studied. For bulk Si, several rebonded missing dimers were found at the surface, while for bulk Ge(100), the surface showed a typical 2×1 reconstruction. All these findings corroborate recent experimental studies and theoretical predictions.

As an attempt to explain polytype formation and crystal growth of SiC we propose an electrostatic model in which electrostatic Coulomb force is considered as an interatomic force. The dependence of surface potential on the stacking sequence of atoms in substrates was investigated, and the growth simulation was tried considering the energetic balance under various interaction lengths.The model predicts the double positioning twin formation and the difference in area between twins in cubic 3C-SiC growth on hexagonal 6H-SiC and rhombohedral 15R-SiC substrates. The prediction was experimentally tested by simultaneous chemical vapor deposition growth on basal planes of 6H-SiC(0001) and 15R-SiC(0001). Polytype and interface structure of both specimens were investigated by reflection high energy electron diffraction (RHEED) and high resolution transmission electron microscopy (HRTEM).

3C-SiC, lattice-matched with TiC, is a candidate for use in wide-bandgap semiconductor devices. Epitaxial 3C-SiC films were grown on (111) and (112) TiC substrates, and defects were characterized by analytical TEM.

In this paper the nucleation mechanisms for SiC thin film growth are studied by rapid thermal CVD and atomic force microscopy (AFM). The nucleation mode was found to be strongly dependent on the hydrocarbon partial pressure in the gas stream, for a fixed reaction time. In the case of three-dimensional (island) growth at low precursor concentration, cross-sectional SEM micrographs indicate that no voids are present at the center of each nucleus (or island). Voids begin to form when two neighboring nuclei come in contact. AFM has shown that trenches are present in the Si substrate around each isolated nucleus. The trench depth increases with the diameter of the island. AFM analysis of films grown for a nominal reaction time of 1 sec at different propane concentrations indicates that: (1) SiC grain size and surface roughness decreases with increasing propane concentration; (2) SiC grain density increases with increasing propane concentration. Based on the above evidence, the following nucleation mechanism is proposed: (a) the initial nucleation density is determined by the precursor concentration in the reaction gas; b) each nucleus grows larger, both laterally and vertically, by consuming Si around it; (c) voids are formed when nuclei grow large enough to come in contact, and not at the original nucleation sites.