Oxygen interaction with CoSi(100) and CoSi 2(100) surfaces

Abstract

The interaction of oxygen with (100) surfaces of single crystalline CoSi and CoSi 2 has been studied using LEED, AES and UPS techniques. Reference experiments at recrystallized Co and (111) oriented Si surfaces are performed to allow comparison with those alloy surfaces. It is found that the oxygen uptake kinetics at CoSi resembles that measured at Co surfaces, whereas at CoSi 2 almost Si-like behaviour is observed. This strongly supports a structure model which exhibits surface reconstruction with enhanced Co concentration at CoSi(100) surfaces. At CoSi 2(100) surfaces the toplayer contains only Si, the second layer may be composed of Si, too. From Auger electron and UP spectra it is seen that the oxygen always is bonded at Si although at CoSi(100) the sticking process occurs via Co atoms.