Structure and optoelectronic properties of spray deposited Mg doped p-CuCrO semiconductor oxide thin films

Transparent p-type Mg doped CuCrO wide-band-gap oxide semiconductor thin films were deposited over quartz substrates by chemical spray technique using metallo-organic precursors. Crystalline single phase CuCrO delafossite structure was dominant in ≥700°C argon ambient annealed films but the as-deposited films contained spinel CuCr O mixed phases. X-ray photoelectron Cr 2p spectra show spin-orbit splitting energy ∼9.8 eV consistent with Cr valance state and Cr 2p resolved peaks show mixed valence state on Cr /Cr confirming CuCrMg O compound phase in spray deposited films. The effect of substrate temperature and film thickness on optical, electrical conductivity, and thermoelectric coefficient was investigated. Highly transparent ≥80% CuCrMgO films with direct and indirect optical band gaps of 3.08 and 2.58 eV for 155 nm and 3.14 and 2.79 for 305 nm thin films, respectively, were obtained. Photoluminescence emission bands at 532 and 484 nm interpreted to arise from 3 d 4 s and 3 d Cu intraband transitions confirm mixing of Cu 3d, 4s, and 4p with O 2p orbitals necessary for realizing p-type CuCrO films. Electrical conductivity of CuCrMg O films ranged 0.6-1 S cm exhibiting activation energies ∼0.11 eV in 300-420°K and ∼0.23 eV in ≥420°K regions ascribed to activated conduction and grain boundary trap assisted conduction, respectively. Transparent p-(CuCrMg O)/n-(ZnO) heterojunction diodes showing rectifying current-voltage characteristics were fabricated. © 2008 American Institute of Physics.