Effect of alumina doping on structural, electrical, and optical properties of sputtered ZnO thin films

A systematic study of the influence of alumina (Al2O3) doping on the optical, electrical, and structural characteristics of sputtered ZnO thin films is reported in this study. The ZnO thin films were prepared on 1737F Corning glass substrates by R.F. magnetron sputtering from a ZnO target mixed with Al2O3 of 0–4 wt.%. X-ray diffraction (XRD) analysis demonstrates that the ZnO thin films with Al2O3 of 0–4 wt.% have a highly (002) preferred orientation with only one intense diffraction peak with a full width at half maximum (FWHM) less than 0.5°. The electrical properties of the Al2O3-doped ZnO thin films appear to be strongly dependent on the Al2O3 concentration. The resistivity of the films decreases from 74 Ω·cm to 2.2 × 10− 3 Ω·cm as the Al2O3 content increases from 0 to 4 wt.%. The optical transmittance of the Al2O3-doped ZnO thin films is studied as a function of wavelength in the range 200–800 nm. It exhibits high transparency in the visible-NIR wavelength region with some interference fringes and sharp ultraviolet absorption edges. The optical bandgap of the Al2O3-doped ZnO thin films show a short-wavelength shift with increasing of Al2O3 content.