Influence Of Co Doping Content On Its Valence State In Zn_(1-x)co_xo (0 ≤ X ≤ 0.15) Thin Films

摘要

Zn_(1-x)Co_xO (0 ≤ x ≤ 0.15) thin films grown on Si (1 0 0) substrates were prepared by a sol-gel technique. The effects of Co doped on the structural, optical properties and surface chemical valence states of the Zn_(1-x)Co_xO (0 ≤ x ≤ 0.15) films were investigated by X-ray diffraction (XRD), ultraviolet-visible spectrometer and X-ray photoelectron spectroscopy (XPS). XRD results show that the Zn_(1-x)Co_xO films retained a hexagonal crystal structure of ZnO with better c-axis preferred orientation compared to the undoped ZnO films. The optical absorption spectra suggest that the optical band-gap of the Zn_(1-x)Co_xO thin films varied from 3.26 to 2.79 eV with increasing Co content from x= 0 to x= 0.15. XPS studies show the possible oxidation states of Co in Zn_(1-x)Co_xO (0 ≤ x ≤ 0.05), Zn_(0-90)Co_(0.10)O and Zn_(0.85)Co_(0.15)O are CoO, Co_3O_4 and Co_2O_3, with an increase of Co content, respectively.