Structural and optical properties of Zn_(1-x)Co_xO thin films fabricated by laser molecular beam epitaxy

摘要

Zn_(1-x)Co_xO thin films on sapphire (0001) substrates were synthesized by laser molecular beam epitaxy (LMBE) method at various temperatures under a work ambient pressure of 5.0 x 10" Pa condition. X-ray diffraction (XRD) spectra, UV-visible transmission spectra and X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) spectra were employed to characterize the properties of samples. All samples were of wurtzite hexagonal structure with the preferential c-axis-orientation. Co~(2+) ions incorporated into ZnO lattice and substituted for Zn~(2+) ions. ZnLMM Auger spectrum implied Zn interstitials existed in sample. The optical transmission of all samples was relatively high in visible region. Two PL emission peaks located at 418 nm and 490 nm were assigned to the electron transition from the Zn interstitials to the top of the valence band and from the Zn interstitials to the Zn vacancies, respectively.