d-electron-dependent transparent conducting oxide of V-doped ZnO thin films

Abstract Transparent conducting oxides (TCOs) have garnered considerable attention because of their promising potential use in optoelectronic devices. The conductivity of conventional TCOs is dependent on s or p electrons. Consideration of the fact that the d electrons have local magnetic moments, if one achieves ferromagnetism in d-electron-based TCOs, then applications in multi-functional devices are possible. In this paper, we report the discovery of a d-electron based TCO material, V-doped ZnO films, which exhibit the resistivity of 2.2 × 10−3 Ω cm at room-temperature and above 85% transmittance in the visible-light region. Such properties can be compared to those of TCOs, such as Zn1-xAlxO and SnO2. Further analysis shows that the V-substituting Zn2+ ions in the ZnO lattice with the 4 + valence state acts as donors that increase the carrier density and optical band-gap with respect to pure ZnO film. Additional first-principle calculations confirm that the V ions’ d electrons play a critical role in the electrical conductivity of the Zn1-xVxO films. Moreover, the Zn1-xVxO films show obvious room-temperature ferromagnetism. Zn1-xVxO film may comprise a new candidate for d-electron-based TCOs.