Effect of r.f. power variation on gallium doped zinc oxide thin films

Abstract

In the present study, 5 wt.% Ga2O3 doped zinc oxide (ZnO:Ga) films were deposited on glass substrates by r.f. magnetron sputtering, at room temperature. r.f. power influence on film characteristics was investigated in a wide variation ranges. Various methods were used to characterize the structural, electrical and optical properties of the films such as XRD, HRSEM-EDS, AFM, four point probe resistivity and optical transmittance. The achieved results revealed that the r.E power variation played a critical role on ZnO:Ga thin films. Especially, the deposition rate increased from 80 angstrom/min to 300 angstrom/min, while resistivity values were obtained around 10(-4) Omega cm. According to XRD results, majority of the thin films were oriented with the crystallographic c-(002) axis perpendicular to the substrate surface. Also, the crystallite sizes of the ZnO:Ga films were larger than ZnO and ZnO:Al thin films. The optical transmittance increased from 71% to 82% with the increase of r.f. power values. Moreover, the surface roughness (RMS) values were in the range of 2.12-15.70 nm. At 230 W r.f. power, the minimum resistivity value was obtained as 3.2 x 10(-4) Omega cm, thickness as 540 nm and RMS as 9.24 nm. The average optical transmittance at 230 W was measured as 79.63% in the visible spectrum and the figure of merit (EOM) value was achieved as 24.8843 x 10(4) (Omega cm)(-1). (C) 2015 Elsevier Ltd. All rights reserved.