Influence of the growth conditions on the transparent conductive properties of ZnO：Al thin films grown by pulsed laser deposition

Abstract

The influences of aluminum doping, oxygen pressure, and substrate temperature on the transparent conductive properties of ZnO:Al (AZO) films grown by pulsed laser deposition (PLD) were investigated using scanning electron microscope, atomic force microscope, X-ray diffraction, Hall effect measurements, and optical transmission spectrum. When the aluminum doping concentration is over 0.5 wt%, all the PLD grown AZO films are degenerated and the aluminum donors are thermal ionized even at a low temperature of 80 K. As a result, the bandgap of AZO film shows blue shifts due to the Bernstein-Moss effect as further confirmed by optical transmission spectrum. The influences of the oxygen pressure and substrate temperature on the transparent conductive property of AZO films were further studied. When the oxygen pressure is 1 Pa and the substrate temperature is 200 ℃, the best conductivity property of AZO thin film is obtained with Hall mobility of 28.8 cm2/V·s and film resistivity of 2.7×10-4 Ω·cm. Moreover, the light transmittance in the visible range exceeds 85%. However, as the oxygen pressure and temperature continue to increase, the film resistivity will increase.