CARBON CONTAMINATION OF SI(111) SURFACES

Auger electron spectra obtained by operating LEED optics with a modulated, swept retarding potential have been used to study cleaning of the Si (111) surface and its subsequent contamination by ethylene vapour under ultra high vacuum conditions. The results provide corroborative evidence of the importance of carbon contamination for the generation of three-dimensional growth centres during epitaxial deposition of Si by pyrolysis of silane at low pressures. The detection level for carbon by this technique has not yet been measured but it is lower than that necessary to produce a recognisable visual change in the Si (111)-7 LEED pattern. The behaviour of the carbon-containing surface layer as a function of heat treatment has been explored and an explanation for the results is given. © 1969.