Growth of transparent conducting nanocrystalline Al doped ZnO thin films by pulsed laser deposition

Nanocrystalline thin films of Al doped ZnO (Al:0–5 at%) with low electrical resistivity and high optical transparency have been grown by pulsed laser deposition. X-ray diffraction patterns showed the presence of hexagonal wurtzite ZnO phase with strong c-axis orientation in all the cases. The c-axis lattice parameter was found to increase with increase in Al doping. The average grain size in the film decreases from ∼38 to ∼25 nm with increasing Al concentration from 0 to 5 at%. For a critical doping of 2 at%, the resistivity of the AZO film is minimum (6×10−4 Ω-cm) and the average optical transparency is nearly 85%. The band gap increases with increase in doping which is in accordance to Burstein–Moss shift. A blue shift in the absorption edge of ZnO with increasing Al concentration in the film is noteworthy as it leads to increase in the width of the transmission window.