Sol-Gel Preparation, Deposition and Characterization of Nanostructured Aluminium Doped Zinc Oxide

Pure and Aluminium-doped ZnO (Zn(1-x)A1(x)O,(0) x = 0 to 5 wt% thin films were deposited onto glass substrate by sol-gel spin coating method. The influence of various aluminium concentration in ZnO thin films on the structural, surface, optical and photoconducting properties were investigated. The GIXRD studies confirmed the polycrystalline nature with wurtzite structure of pure and Al doped ZnO films. Films with 1.5 % concentration of aluminium showed maximum absorption and transmission in the UV and visible regions respectively. The FESEM images showed crack free films with increasing grain boundaries upon doping. The average grain size is found to decrease due to aluminium doping. AFM images showed doped films with 1.5 % have better smoothness than other films. The photoconductivity measurements reveal that there is increase in the photocurrent compared to dark current for the Al doped ZnO. The photocurrent reaches its maximum value for ZnO: A1-1.5 % and then decreases upon increase in Al concentration. The photoresponse has slightly degraded upon aluminium doping onto ZnO. Temperature dependent conductivity shows that the thermal activation energy for the film decreases up to 1.5 % aluminium concentration and then increases for other concentrations in the temperature range 308 to 375K.