Effect of oxygen partial pressure on the Fermi level of ZnO1-x films fabricated by pulsed laser deposition

We investigated the influence of oxygen deficiency on the Fermi level (E-F) of ZnO thin film prepared by pulsed laser deposition (PLD). For this purpose, we adopted in situ x-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy. The oxygen deficiency was effectively controlled by varying the oxygen partial pressure [P(O-2)] during the PLD. The E-F shifted by +0.6 eV as the P(O-2) decreased from 10 to 3.3 Pa. This shift indicates a significant change in the energy balance in the oxygen-deficient ZnO films. This fact suggests that the very large change in the resistivity of ZnO thin films resulting from the oxygen deficiency could be attributed to the E-F shift rather than grain boundary formation in the ZnO film. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3432398]