Temperature Dependent Studies on Radio Frequency Sputtered Al Doped ZnO Thin Film
Abstract
In this work, highly conductive and transparent Al:ZnO (Al doped ZnO, i.e., AZO) thin films were grown by radio frequency (RF) magnetron sputtering technique at a typical deposition temperature. The effect of deposition temperature on the structural, morphological, optical and electrical properties was studied. The x-ray diffraction (XRD) studies revealed a hexagonal wurtzite crystal structure for all AZO layers with a (002) preferred orientation along the c-axis. Columnar, compact, uniform grain growth of the layer was observed from atomic force microscopy (AFM) images. The deposition temperature had an influence on the surface roughness and average grain size of deposited films, which could be confirmed by means of AFM images. Optical studies confirmed that both optical band gap energy and urbach energy were influenced by the substrate temperature. Highly transparent films with an energy band gap ranging from 3.48 to 3.65 eV were obtained upon changing the deposition temperature from 22 to 400 ℃ . The presence of defects was confirmed by photoluminescence (PL) spectra. A systematic measurement of the electrical parameters like barrier height, and ideality factor of the devices (Ag/Al:ZnO) was carried out with the help of I-V characteristic. This study may be useful for the design and fabrication of AZO based electrodes for solar cell applications.
