INVESTIGATION OF DIFFERENT OXIDATION PROCESSES FOR POROUS SI BY XPS

The oxidation behaviour of porous Si films formed on p-type doped subs trates has been investigated. On freshly prepared porous Si no oxygen is found. During the native oxidation suboxides are formed. For low p- doped samples SiO2 is formed after 1000 h, whereas on highly doped sam ples only Si2O is found. Part of the difference between low and high d oped substrates is probably due to different orientations of the inner surfaces. It seems that the orientation of the inner surfaces of poro us Si films formed on p(+)-doped substrates is more preferentially (11 1) than it is the case for the lower doped samples. For the anodic oxi dation process also suboxide formation is found which results in the f ormation of SiO2.