Native oxides and carbon contamination removal from InAs(100) surface by molecular hydrogen flow at moderate substrate temperatures: Stoichiometric and morphological studiesWe have observed the nucleation and growth of the Cu 2 O surface oxide on a Cu͑100͒ surface at 870 K using low energy electron microscopy. Nucleating on a surface exhibiting the ͑ ͱ 2 ϫ 2 ͱ 2͒R45°-O overlayer, this phase caused the overall step morphology to change from long, mostly straight narrow-terraced step bunches to broad, deeply curved terraces with more highly bunched steps. Using x-ray photoelectron spectroscopy, we have measured an upper bound of 2.6 ML ͑monolayer͒ for the surface oxygen coverage at which we observed this oxide phase. The lattice constant of the observed oxide phase matches that of the ͑111͒ face of Cu 2 O. We postulate that the oxide does not form epitaxially on this surface at this temperature due to interactions with the centered rectangular phase of oxygen, which provides a nearly hexagonal template for the Cu 2 O͑111͒ hexagonal structure.

ABSTRACT:The surface of rubbed polyimide films was studied as a function of the film thickness and applied load using atomic force microscopy (AFM). Three dominant consequences of rubbing on the film topography were observed: scratches confined to the near surface of the film, tears that extended to the substrate, and strings of islands or droplets aligned parallel to the rubbing direction. Tears, found only in films less than 50 nm thick, varied in areal density and shape due to variations in the film thickness, rubbing load, and adhesion to the substrate. Strings of droplets aligned in the rubbing direction were seen on most samples without discernible dependence on the thickness or rubbing load.

ABSTRACT:The thermal histories of polyimide films were varied to study the effect of the extent of imidization on the response of films to rubbing. Films rubbed prior to imidization formed tears that extended to the substrate; tears in these films formed at smaller film thicknesses than in films imidized prior to rubbing. Aligned nanoscopic islands were also seen. The alignment of these islands disappeared upon imidization. Films imidized at a low temperature showed less alignment of islands than conventionally prepared films.

An in situ technique that uses a stylus profilometer has been developed for studying current-induced thermal expansion in printed conductive traces and for investigating the effects of expansion on trace resistance and power handling. It was employed to study printed silver traces (50-100 μm linewidths) subjected to a pulsed, millisecond-range current. The traces were aerosol jet printed on a glass substrate using a commercial nanoparticle-based ink. At low peak current densities (J p <5×10 4 A mm −2 ), trace expansion is reversible with no permanent resistance increase. At J p 5×10 4 A mm −2 the expansion becomes irreversible, resulting in reduced power handling and a permanent resistance increase of up to 50%. Since the irreversible expansion decreases density and weakens nanoparticle connectivity, further expansion easily distends the material to the point of forming a void. This is one breakdown mechanism of printed nanoparticle-based silver at high pulsed current.