Structure and optical properties of CdS:O thin films

We have studied structure and optical properties of CdS:O thin films deposited on soda lime glass substrates by rf magnetron sputtering in the atmosphere of oxygen/argon gases. According to X-ray diffraction and confocal Raman scattering data, the films deposited under oxygen partial pressure below 3% show crystalline structure of CdS. On the other hand, X-ray diffraction, confocal Raman scattering, TEM (transmission electron microscopy) and XPS (X-ray photoelectron spectroscopy) data are indicative of amorphization, nano-crystallization, and inclusion of CdO2 in CdS:O thin films obtained under oxygen partial pressure of 5%. The last films have shown significantly increased transmittance in a spectral range above the energy gap of CdS. The origin of this transmittance is discussed by taking into account redistribution of electronic density-of-states in amorphous phase, quantum size effect and contribution of CdO2.