Theoretical and experimental investigation of W doped ZnO

Abstract

The properties of high valence difference W doped ZnO films (WZO) are investigated by means of plane wave pseudo-potential method based on the density-functional theory (DFT) and pulsed DC magnetron sputtering technique. The theoretical result shows after incorporation of W the Fermi level enters into the conduction band, showing that a typical n-type metallic characteristic and the optical band gap Eg* increase significantly. The carriers originate from the orbits of W 5d, O 2p and Zn 3d. Moreover, the increase of the lattice constant is due to the longer bond length of W-O and lattice distortion. The experimental results demonstrate that the deposited WZO film grows preferentially in the (002) crystallographic direction but the lattice constant increases. The resistivity decreases from 1.35 10-2 cm to 1.55 10-3 cm and the optical bandgap extends from 3.27 eV to 3.48 eV compared with those of ZnO. The average transmittance is over 83 % in a wavelength range from 400 to 1100 nm. The experimental results are in good agreement with the theoretical results, showing that the WZO thin film has a great potential application as transparent conductive oxide.