GROWTH OF COBALT OVERLAYERS ONTO SI(100)

The growth of evaporated Co overlayers onto Si(100) at 350 K was studi ed using Auger electron spectroscopy. Cobalt 5N was evaporated at a ra te of almost-equal-to 0.4 monolayers/min from a filament. The amount d eposited was monitored with a quartz crystal microbalance with a resol ution of 0.2 monolayers. The changes in the L23 VV Si as well as in th e cobalt LMM and MVV Auger transitions were followed. The growth mode of Co and onto Si(100) surface depends strongly on the presence of oxy gen. Without oxygen a diffusion front of Co is found after deposition of almost-equal-to 4 monolayers. In the presence of oxygen (5 x 10(-10 ) mbar), Si atoms diffuse to the surface, the adsorbed oxygen acting a s the driving force with possible building of CoSi and Co2Si. The admi tted oxygen does not cause detectable oxidation of the Si surface nor of the Co overlayer. A thin layer of SiO2 can be formed on the Si surf ace by O2+ bombardment, acting as a diffusion barrier to Co overlayers .