X-Ray photoelectron spectroscopy study of CdTe oxide films grown by rf sputtering with an Ar–NH 3 plasma

Abstract

CdTe oxide films were prepared on glass substrates using the rf-sputtering technique and a controlled plasma of Ar–NH 3. Films were studied by X-ray photoelectron spectroscopy and X-ray diffraction. The changes in chemical composition as a function of NH 3 partial pressure during deposition indicate that oxygen incorporates in the films up to approximately 62 at.%, while the Cd and Te contents decrease from ∼43 to 19 at.%. At NH 3 partial pressure of 1.3×10 −2 Pa, the Te–Cd bonds are strongly reduced and the Te in the films is mainly bonded to oxygen. The Cd MNN X-ray Auger feature shows a shift in energy of approximately 0.8 eV as a function of NH 3 partial pressure. This shift appears to be related to the change in Cd bonding from Cd–Te to Cd–O. Films prepared at NH 3 partial pressure of 4×10 −4 Pa present crystallinity with a [111] cubic CdTe orientation, while those prepared at higher NH 3 partial pressure show an amorphous structure. The amorphous material formed at NH 3 partial pressure saturation appears to be mainly amorphous CdTeO 3.