Cleanliness and Pollution of Si(111) and Si(100) Surfaces Studied by AES

The direct Auger spectra E (E) of Si have been studied for (111) and (100) crystals, the surfaces of which have been cleaned or contaminated with either or both carbon or oxygen. The measurement of the peak to background ratio (P/B) for the Si LVV transition is a criterion of cleanliness more sensitive than the appearance of the peaks of the contaminating species (especially for oxygen). Under a base pressure of 1 x 10 exp --10 Torr, and exposure of a sampled area of 15 mu m diameters to an electron beam of high intensity (3 keV, a few A/cm exp 2 ), the whole surface of a crystal can be rapidly polluted with C and O. Oxygen has a great effect on the P/B ratio and the shape of the Si LVV peak, definitely more important than what would be supposed from the weak intensity of the oxygen peak. 18 ref.--AA