Thermally Annealed in Vacuum Undoped and Al-Doped ZnO Thin Films for Multifunctional Applications

Undoped and Al-doped ZnO thin films have been prepared by spray pyrolysis in oxygen and argon atmospheres. The structural properties of ZnO thin films were investigated using atomic force microscopy (AFM) and X-ray diffraction (XRD). The optical properties were studied by UV-VIS spectroscopy and photoluminescence (PL) at room temperature. The electrical resistivity and Hall mobility were measured using the van der Pauw technique at room temperature. AFM studies show that the ambient atmosphere influences the roughness parameters of the ZnO surfaces. The XRD results revealed that undoped and Al-doped ZnO films are polycrystalline and developed [0002] preferred orientation. The best electrical parameters (conductivity, mobility carriers and carrier concentration) are obtained for 1.0 at % of Al-doped ZnO synthetized in Ar atmosphere. In all cases, the electrical parameters under Ar are higher than under O-2 atmosphere, unless they are not doped. Different applications of undoped and Al-doped ZnO thin films are discussed.