ANGLE-DEPENDENT XPS ANALYSIS OF (NH4)(2)S-X-TREATED INP(001) SURFACES

Angle-dependent high-resolution XPS spectra of S 2p, In 3d(5/2) and P 2p have been measured on the InP(001) sample etched chemically, treate d with (NH4)(2)S-x at room temperature (RT), exposed to air at RT and annealed at 400 degrees C in a vacuum. Three kinds (S-I, S-II and S-II I) of chemical states of sulphur an the (NH4)(2)S-x-treated InP(001) s urface at RT are found. It is suggested that S-I. S-II and S-III corre spond to sulphur in the bunk, sulphur bridge-bonded to indium on the s urface and elemental sulphur, respectively. Chemical state of S-III is decreased for the treated sample exposed to air at RT for 1 month, It is removed upon annealing the sample at 400 degrees C inn a vacuum, w hile S-I and S-II remain on the surface. The thickness of the sulphide layer on the annealed surface is estimated to be about one monolayer. Angle-dependent XPS spectra of S 2p and In 3d(5/2) are discussed.