K PROMOTED OXIDATION AND NITRIDATION ON INP(100) SURFACE - A SOFT-X-RAY PHOTOEMISSION-STUDY

The effects of exposure of molecular nitrogen and oxygen on p-type InP (100) surfaces modified by potassium overlayers were studied by core l evel and valence band (VB) photoemission using synchrotron radiation. On the K pre-covered surface, the potassium coverage enhanced the nitr ogen and oxygen sticking coefficients dramatically. As far as the proc ess of nitrogen adsorption is concerned, nitrogen atoms react mainly w ith P atoms rather than not react directly with indium atoms. Two kind s of nitride complexes, InPNx and InPNx+y were formed at the K-precove red InP(100) surface. In case of oxygen adsorption, O may bond with K and produce the peroxides O-2(2-) and superoxides O-2(-). Following th is a few kinds of phosphate phases, In(PO4)(x), were formed on the sur face. In comparison with InP(110) surface, we found that the oxidation and nitridation promotion for the InP(100) surface was much stronger. The reasons may be the number of surface defects as well as the polar ity of the InP(100) surface.