Effects of Annealing Temperature on Optical and Electrical Conductivity of (80 nm ITO)/(100 nm ZnO) Transparent Conducting Oxide Multilayer

Conductive and transparent multilayer films consisting of two layers (ITO/ZnO) have been fabricated as Transparent Conducting Oxides (TCO). 100 nm ZnO film was deposited on 80 nm Indium Tin Oxide (ITO) film by thermal evaporation in a residual pressure of 10-5 Torr and the films were annealed at 400 °C and 500°C for 60 minutes in Tubular furnace. The as-grown and the annealed films were characterized using Powder x-ray Diffractometer (PXRD) for the phase identification of the materials and UV-Visible Spectrophotometer for the photometric measurements. Beer's Lambert equation was employed to estimate the absorbance of each film under study. Four point probes based instrument was used to measure the average resistance of the films. The sheet resistance of the film was calculated from the electrical resistance of the material. The results revealed that the transmittance spectra of (80 nm ITO/100 nm ZnO) multilayer films depend strongly on the annealing temperatures and the wavelength. Optical transmittance of about 95% was estimated for the 400 °C annealed film in the ultraviolet and visible region and relatively decreases towards the infrared region of the solar spectrum. The average electrical conductivity of 14000 (ohm.cm)-1 was also estimated for the 400 °C annealed film. Rhombohedral centered and hexagonal lattice structures were identified for the ITO and ZnO films respectively. 80 nm ITO/100 nm ZnO multilayer films annealed at 400 °C is hereby recommended as a good TCO for solar cells applications.