Structural studies of hydrogenated amorphous germanium and hydrogenated amorphous silicon germanium alloys.

摘要

The structural properties of hydrogenated amorphous germanium and silicon germanium alloys, prepared using the r.f. glow discharge method, were studied using transmission and scanning electron microscopy, gas evolution, differential scanning calorimetry and infrared absorption spectroscopy techniques. In particular, the presence or absence of a two phase microstructure was monitored as a variety of deposition parameters was systematically varied. For each set of deposition conditions, samples were made for both structural and opto-electronic analysis in order that variations in the film microstructure could be correlated with possible changes in the material's photoelectronic properties.;The structural measurements indicated that the two phase microstructure was absent from the hydrogenated amorphous germanium and silicon germanium alloy films deposited on the powered electrode under conditions of moderate applied powers and small electrode separations. They also showed that, in contrast to those prepared on the unpowered electrode, these films contained significant amounts of unbounded hydrogen. The photoelectronic properties for these films were far superior to those for films having the two phase microstructure with ;Amorphous germanium films deposited on the unpowered electrode at substrate temperatures less than 250