The effects of post heat treatment on ITO/AgAl/ITO/p-Si multilayer films

Abstract

For the past few decades, the quest for an improve indium tin oxide (ITO) films have attracted a lot of interest by scientists and industries for application in advanced optoelectronic devices. ITO/AgAl/ITO multilayer films were deposited on p-silicon (Si) substrates at room temperature by radio frequency (RF) and direct current (DC) magnetron sputtering respectively. The effects of post-heat (annealing) treatment on the structural, optical and electrical properties of the ITO/AgAl/ITO multilayer films were investigated at different temperature of 200 °C, 300 °C, 400 °C and 500 °C respectively. X-ray diffraction (XRD) results reveal an amorphous structure for the as-deposited film whereas the post annealed films show a polycrystalline and cubic bixbyite structure with preferential peaks orientation along ITO (222), Ag (111), and ITO (440) crystalline directions. Atomic force microscopy (AFM) analysis indicates a smoother surface morphology and improved grain size after post heat treatment. Ultraviolet-visible spectrophotometer measurements show a significant increase in optical transmittance spectra as the annealing temperature increases. Maximum transmittance peak of 87.2 % was obtained by film annealed at 500 °C. Four-point probe measurements exhibit a substantial decrease in sheet resistance with respect to increasing post-annealing temperature. The sheet resistance of the as-deposited film is about 7.85 Ω/sq and falls down to 3.23 Ω/sq as the post-heat temperature is increased to 500 °C. Compared to as-deposited film, the post annealed multilayer films optical and electrical properties have been successfully enhanced, fine turned and favourable for Si solar cell application.