Improved physical properties of spray pyrolysed Al:CdO nanocrystalline thin films

Abstract

Pure and Al doped CdO thin films were coated on glass substrate at 400 °C by spray pyrolysis method for various aluminium concentrations (3, 5, 10 and 15 wt%). Al doped CdO thin films were characterized by various techniques such as X-ray diffraction, SEM, UV–visible spectroscopy and Hall measurements. XRD diffraction patterns reveal that the films are polycrystalline in nature exhibiting face centered cubic structure. The prominent peak corresponds to (200) plane and the corresponding calculated crystallite size varies from 12 to 18 nm. SEM images show that the films exhibit grains of uniform size which are agglomerated for films with higher dopant concentration. It is found that the optical transmittance decreases with the increase in Al concentration and the optical energy band gaps vary from 2.08 to 2.49 eV for various Al doping concentration levels. Electrical studies done using Hall measurement system exhibit that the undoped and Al doped CdO films are n-type semiconductors with carrier concentration in the order of 1021 cm−3. The electrical resistivity of the Al:CdO films ranges from 4.903 × 10−3 to 9.358 × 10−3 Ω cm.