BONDING PARTNER CHANGE REACTION IN OXIDATION OF GE ON SI(001) - OBSERVATION OF 2-STEP FORMATION OF SIO2

Oxidation of 5 angstrom Ge deposited at room temperature on Si(001) an d the dependence of temperature on the oxidation behavior are investig ated by employing synchrotron radiation photoelectron spectroscopy. Th e sample on exposure to air forms a mixture of Ge oxides and a small a mount of Si oxides. Upon annealing, oxygen changes its bonding partner from Ge to Si forming SiO2 as the predominant final product. Two dist inct steps have been observed in such a reaction. First step is the cl eavage of all the Ge-O bonds and formation of Si-O bonds to form mainl y Si suboxide. The second step is the rearrangement of Si-O bonds to f orm SiO2. The former one takes place in the temperature range 200-300- degrees-C whereas the latter one in the range 300-600-degrees-C.