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Il-VI WORKSHOP PurposeThe purpose of this Workshop is to bring together the universities and the industrial and governmental communities that work with II-VI materials which include HgCdTe and other IR materials, Il-VI semiconductor alloys used for x-ray and y-ray detectors, ZnSe-based Il-VI photonic materials, and II:VI photorefractive materials. The Workshop aims at advancing the understanding of the physics and chemistry of these materials. Areas of InterestAreas covered include a broad range of disciplines: materials engineering, intrinsio?' and extrinsic defects including doping, surface sciences, manufacturing/processing, electrical, optical, and magneto-optical properties as well as interactions between them. Workshop FormatTo provide more discussion time, the Workshop program will consist of about 50 papers.When appropriate, invited, encouraged, and contributed papers with a common theme will be grouped for presentation and then followed by an extensive discussion period. Scheduled morning and afternoon breaks as well as lunch, provided as part of the workshop fee, can also be used as additional discussion time. To further promote informal discussion and interaction, the first two days will conclude with a wine and: cheese break accompanied by table-top displays from commercial vendors displaying products and services of interest to the community.

Conventional and high-resolution transmission electron microscopy are used to characterize the initial stages of AlN thin-film growth. AlN films are deposited by molecular beam epitaxy onto annealed (0001) oriented α-Al2O3 (sapphire) substrates. During the initial stages of film growth (film thickness ∼25 nm) AlN forms islands of varying alignment with the Al2O3 substrate. Some of the AlN islands are well aligned with the [112̄0]AlN∥[101̄0] Al2O3 and (0001)AlN∥(0001)Al2O3, which matches closed-packed planes and directions. Other islands exhibit either an alignment of one set of planes, i.e., grains are aligned with the (11̄01)AlN∥(112̄0) Al2O3, or are misaligned with respect to the Al2O3 substrate. As the AlN film grows in thickness (film thickness ∼100 nm), the film becomes continuous, and the closed-packed planes and directions of the film and substrate are aligned for the majority of the film. Islands of AlN with an alignment other than this predominant orientation disturb the growth near the AlN/Al2O3 interface and create displacements along the [0001] AlN direction in overlying AlN grains. These misaligned AlN grains provide one source for the formation of planar defects in the epitaxial AlN films. The evolution of the AlN film microstructure and the reasons for the observed orientation relationships are discussed.

Grain boundaries and twin boundaries in commercial Cd1−xZnxTe, which is prepared by a high-pressure Bridgeman technique, have been investigated with transmission electron microscopy, scanning electron microscopy, infrared-light microscopy and visible-light microscopy. Boundaries inside these materials were found to be decorated with Te precipitates. The shape and local density of the precipitates were found to depend on the particular boundary. For precipitates that decorate grain boundaries, their microstructure was found to consist of a single, saucer-shaped grain of hexagonal Te (space group P3121). Analysis of a Te precipate by selected-area diffraction revealed the Te to be aligned with the surrounding Cd1−xZnxTe grains. This alignment was found to match the (111) Cd1−xZnxTe planes with the (0111) planes of hexagonal Te. Crystallographic alignments between the Cd1−xZnxTe grains were also observed for a high-angle grain boundary. The structures of the grain boundaries and the Te/C1−xZnxTe interface are discussed.

The microstructure and chemical inhomogeneities of commercially available Cdl-,Zn,Te (CZT) have been evaluated using electron microscopy and microanalytical techniques. Since imperfections, such as inclusions, cracks and extended crystallographic defects are known to affect the performance of CZT gamma-ray spectrometers, understanding the nature and origins of such imperfections is vital to the improvement of device performance. CZT that is grown using a high-pressure Bridgeman method has a polycrystalline microstructure that contains numerous grain boundaries, twins and inclusions. In this study, scanning electron microscopy and X-ray energy-dispersive spectroscopy were used to analyze inclusions and cracks inside CZT material. Such analysis found regions of material rich in C, 0, Si, Zn and Te. Transmission electron microscopy revealed small subgrains and thin platelets of a second phase material located inside the large-grain CZT matrix. Details of these microstructural features and their possible origins are discussed.

Pulsed-laser ablation was used to deposit copper oxide onto single-crystal substrates of (0001) OC-AI2O3 at temperatures ranging up to 900°C. Prior to deposition, the substrates were chemically cleaned and annealed to create a surface structure of low-index terraces separated by crystallographic steps. After deposition, the samples were characterized using transmission electron microscopy and scanning electron Microscopy.The deposited film evolved by an island growth process, with the morphology of the particles being dependent on the growth conditions, substrate orientation, and nature of the substrate surface. Both CuO and Cu2O were produced by the depositions. The phase observed changed from CuO to Cu2O with increasing deposition temperature, as would be expected based on the equilibrium phase diagram. In depositions performed on (0001) alumina substrates with widely spaced surface steps, it was found that on some surface terraces one characteristic particle morphology was produced whereas on others a second morphology was dominant. This suggests that the plane of surface termination in the alumina lattice, which consists of a layer of either Al or O in this orientation, is influencing the growth process.