Synthesis, structural and optical properties of Mo-Doped ZnO Thin Films

Transparent zinc oxide thin films doped with molybdenum have been prepared using a DC reactive magnetron sputtering on glass substrates from metallic ZnMo target. The three films, called A, B, and C, had 1.9 at.% Mo, 2.8 at.% Mo and 4.7 at.% Mo, respectively. The composition of the films was determined by X-ray photoelectron spectroscopy. The analysis of Mo 3d_5/2 core level spectra indicated that Mo exist in the films in Mo⁶⁺ oxidation state irrespective of the Mo content in the film. The X-ray diffraction spectrum of film A showed a texture along the 002 orientation, while that of film B showed two peaks, one at 0 ∼ 34:5° and the other at ∼ 36:5° corresponding to 002 and 101 orientations, respectively. Film C showed two small peaks corresponding to 100 and 110 orientations. Optical measurements showed that all three films had a transmittance of about 80%. The energy band gap showed a linear increase as Mo concentration increases from 3.29 eV to 3.38 eV. The atomic force microscopy image of film A showed a homogeneous morphology of the surface of the film, while the atomic force microscopy images of films B and C showed an inhomogeneous one.