EFFECTS OF Ar+ SPUTTERING ON VALENCE STATE AND CHEMICAL ENVIRONMENT OF COBALT IN COBALT-DOPED ZINC OXIDE

Abstract

Zn1-xCoxAl0.01O (x = 0, 0.15, 0.2, 0.3) films were fabricated on Si(100) substrates by pulsed laser deposition (PLD). X-ray diffraction (XRD) studies showed that the Co-doped ZnO films are polycrystalline with c-axis orientated wurtzite structure. Photoemission revealed a valence state of 2+ and a tetrahedral coordination of Co in the Co-doped ZnO. Ar+ sputtering was performed to investigate the changes to the valence state and the chemical environment of Co at surface and bulk. After Ar+ sputtering, the film composition was found to be closer to the starting target material. This was confirmed by the results of X-ray fluorescence (XRF) measurements, indicating the Co-doped ZnO film surface is cobalt-rich.