Showing papers by "Christopher J. Kiely published in 1987"

On the atomic structure of the Pd2Si/(111)Si interface

Abstract: The structure of the epitaxial Pd2Si/(111)Si interface has been investigated by transmission electron microscopy (TEM). Lattice imaging and conventional TEM on plan-view specimens show that the Pd2Si grains are often misoriented, by typically 4° → 7°, from the epitaxial relation of (0001)Pd2Si//(111)Si, [1010]Pd2Si//[011]Si. Quantitative texture measurements made by taking convergent-beam diffraction patterns from areas containing individual Pd2Si grains show that misorientations are mostly described by tilting about directions in the film plane. Lattice imaging in (100) cross-sectional samples reveals more clearly the nature of the Pd2Si/(111)Si interface and also shows that individual Pd2Si grains may be considerably bent. The origin of the grain misorientations and their significance in understanding the atomic structure of the Pd2Si/(111)Si interface is discussed.

Epitaxial Growth of Thin Ge Films on [001] Gaas by Laser Photochemical Vapor Deposition from GeH4

Abstract: Epitaxial Ge films have been grown on [001] GaAs for substrate temperatures (Ts) as low as 285°C by photodissociating GeH4 at 193 nm in parallel geometry. For a laser fluence of ~15 mJ - cm-2, the film growth rate varies from 0.6 to ~5 nm - min-1, depending upon Ts and gas pressure. Plan and cross-sectional TEM studies of the Ge/GaAs bicrystal demonstrate that the 400–700 A thick Ge films are single crystal and epitaxial with the substrate. The present limitation on epitaxial film thickness appears to be imposed by reduced adatom mobility at the temperatures investigated.

A TEM Study of the Structure of Polycrystalline Si Films on (111) Si Substrates Grown by Low Pressure Chemical Vapor Deposition

Abstract: A systematic series of films have been deposited on Si (111) wafers by the pyrolytic decomposition of disilane in a low pressure CVD reactor at temperatures below 765°C, at a variety of Si2H6 partial pressures. Usually, large columnar Si grains nucleate with the [110] fiber axis parallel to the [111] substrate normal, and exhibit a random arrangement of azimuthal orientations about this axis. Fine scale microtwinning and sub-grain boundaries which are often seen within individual columnar grains have been characterized by HREM. The facetted boundaries between individual columnar grains have also been characterized. The correlation between typical grain size, defect densities and Si2H6 partial pressure is presented and the effect of changing partial pressure during growth is shown to be detrimental to film quality. Finally it is noted that randomly oriented polycrystalline Si films can be formed under certain growth conditions.