PREPARATION, STRUCTURE, AND COMPOSITION OF ORDERED TIN-OXIDE OVERLAYERS ON THE AU(111) SURFACE

Previous work has described the growth mode of tin deposits on the Au( 111) surface and the subsequent oxidation of the tin at room temperatu re. Because the gold does not oxidize under the conditions of this exp eriment, one can monitor the growth of the oxide layer in an increment al fashion. This paper extends the study to oxidation at higher temper atures. From 500 to 800 K at about 10(-6) Torr of oxygen, at least hal f the tin in-diffuses, with the rest forming an ordered SnO2 layer on the surface. This ordered oxide has no counterpart for bulk tin, which melts at 505 K. Heating above 800 K causes diffusion of the remaining tin and oxygen into the gold substrate. The formation of the oxide la yer has been studied by Auger spectroscopy, electron-energy-loss spect roscopy, work-function measurements, and low-energy-electron diffracti on.