Influence of deposition temperature on structural, optical and electrical properties of sputtered Al doped ZnO thin films

Al doped ZnO thin films have been deposited by DC magnetron sputtering technique from ZnO–2 wt.% Al2O3 target onto glass and oxidized silicon substrates heated at temperature ranging between 150 and 370 °C in Ar plasma. X-ray diffraction analysis shows that the deposits have a preferential growth along the c-axis of the hexagonal structure. The average grain size increases from 10 to 59 nm with temperatures ranging from 150 up to 330 °C then it decreases to 45 nm at 370 °C. The root main square (RMS) surface roughness decreases with substrate temperature from 20.9 to 4.1 nm. The films are transparent up to 90% in the visible wavelength range and the optical gap increases with substrate temperature from 3.41 to 3.64 eV. The resistivity measured in Van der Pauw configuration at room temperature is very sensitive to the substrate temperature. It decreases from 5 × 10−4 to 3 × 10−5 Ω cm when the deposition temperature increases from 150 to 370 °C. Both carrier mobility and carrier concentration were found to increase with substrate temperature.

► Al doped ZnO as transparent conducting oxide.
► Al doping enhances physical properties of ZnO films.
► Substrate temperature influences structure, morphology and physical properties of ZnO:Al films.
► The RMS surface roughness decreases with substrate temperature.
► Both carrier mobility and carrier concentration increase with substrate temperature.