Structural and optical characterization of RF sputtered CdMgZnO thin film with different Cd concentrations

Abstract

CdMgZnO (CMZO) thin films oriented along the c-axis with various Cd concentrations were deposited on Si substrate using radio frequency (RF) magnetron sputtering. The thin-film crystal structure, narrowing of the optical band gap, and photoluminescence depended on the Cd concentration. Cd concentration from 0% -to-2.5% increased the grain size of the thin films from 24.03 nm to 45.34 nm and decreased the texture fraction of (002) peak (TF(002)) by 9.6%. With the grain size increase in the thin films, the optical band gap narrowed to lower energies and decreased from 3.55 to 3.45 eV due to conduction band adjustment and the valence band repulsion effect from increasing Cd. The photoluminescence properties of all CMZO thin films were strong in the UV region. The thin film grown at 1.5% of Cd showed a broad yellow emission at 581 nm that is optically active due to a defect of oxygen interstitial (Oi). Defect emissions of blue, orange, and red intensities were found to decrease rapidly with the increasing Cd concentration depleting the recombination of photo-generated holes or charge carriers significantly.