Influence of Co doping content on its valence state in Zn1―xCoxO (0 ≤ x ≤ 0.15) thin films

• Published in: Applied surface science Vol. 255; no. 9; pp. 4992 - 4995
• Main Authors: LING WEI, ZONGHUI LI, ZHANG, W. F
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier 15.02.2009
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Physics; 82.80.Ej; 31.15.Rh; Cobalt; 61.72.Vv; Thin films; Valence; Transition elements; 73.61.Ga; Zinc oxide; XPS; Valence state; X-ray photoelectron spectra; Cobalt doping
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2008.12.064

Zn1-xCoxO (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 Zn1-xCoxO (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 Zn1-xCoxO 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 Zn1-xCoxO 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 Zn1-xCoxO (0 < = x < = 0.05), Zn0.90Co0.10O and Zn0.85Co0.15O are CoO, Co3O4 and Co2O3, with an increase of Co content, respectively.