Planar interfaces: Synthesis and high resolution chemistry and structure analysis. Progress report, March 1, 1997--February 28, 1998

The interface synthesis unit is operational and working well. The authors have synthesized interfaces between substrates of austenitic stainless steel, silicon, silicon/niobium, and alumina with and without addition of other materials in the interfaces. Early in the synthesis work it was apparent that substrate surface preparation was critical, along with the usual variables: temperature, time, and pressure. After suitable surface preparation successful interfaces were bonded. Substrate surface preparation requires surface cleaning, to activate the surface and polishing to flatten the bonding surfaces. Flatness has two components: large scale flatness and short wavelength near atomic scale flatness. Analytical TEM electron energy loss (ELS) and energy dispersive x-ray (EDS) nanospectroscopies showed that no detectable oxygen contamination occurred in any of the interfaces they have synthesized, in particular in the stainless steel interfaces containing Ti or Cu. Those two interfaces were especially stringent tests of the synthesis unit because of the high reactivity of Ti and Cu with oxygen. Single crystal Si {l_brace}100{r_brace} substrates are more useful than polycrystalline stainless steel for determining the effect of ion cleaning induced roughness on interface morphology. Nb was deposited at room temperature on ion-cleaned and as-received Si wafers to evaluate this effect in edge-on transmission geometry. The authors have extended their work on contacts for GaN to TiN/GaN interfaces and Au/Ti/GaN multilayer interfaces. Some recent results from the GaN contact research are given in Smith et. al. (1996a) and Smith et. al. (1996b). The authors have evaluated the usefulness of one of the new oxygen plasma cleaning units for prevention of carbonaceous contamination build-up on TEM specimens. It proved very successful