THERMAL OXIDE ON CDSE

X-ray photoelectron spectroscopy (XPS) has been used to characterize t he thin thermal oxide film grown on single crystal CdSe(0001) and poly crystalline CdSe by exposure to O-2(dry air) at 350 degrees C. SeOx sp ecies, where x=2,3, are clearly identified by a 5 eV shift of the Se 3 d(3/2,5/2) peaks to higher binding energy. A very weak shift to lower binding energy is observed for the Cd peaks. The positions of the Cd a nd O peaks do not match those found for the known cadmium oxides, CdO and CdO2. Instead, it is proposed that the Cd bound oxygen atoms occup y substitutional Se sites. The presence of Cd bound oxygen can also be inferred from the intensities of the SeOx, Cd, and O peaks, Raman spe ctroscopy confirms the existence of O in Se substitutional sites. Angl e-resolved XPS is used to determine the thickness of the oxide and the relative amount of SeOx and Cd bound oxygen. The XPS data are consist ent with an 8-9 Angstrom thick oxide where similar to 60% of the oxyge n is bound to Se and similar to 40 is bound to Cd. The data show that the oxide structure contains two layers; a passivation layer made of t he SeOx species and, underneath, a layer containing oxygen in Se subst itutional sites. (C) 1997 American Institute of Physics.