Influence of sputtering power on surface topography, microstructure and mechanical properties of aluminum thin films

Abstract

The article reports on the influence of sputtering power on surface topography, microstructure and mechanical properties of aluminum thin films sputtered on mild steel substrates. The Al thin films were deposited on mild steel substrate at varying RF power of 150 W, 250 W, 300 W, and 350 W and at a constant substrate temperature of 90 Degree. The films were characterized by optical surface profiler (OSP), field emission scanning electron microscopy (FESEM) and nanoindentation. The highest average and root mean square roughness values were obtained at 250 W while the lowest at 350 W. The highest and smallest Rt values were obtained at 150 W and 350 W respectively. The lowest and highest Rp values were determined at 350 W and 250 W respectively. The lowest hardness and modulus were obtained at 250 W while the highest values were determined on films sputtered at 150 W. The FESEM micrographs revealed that at 150 W the structure consisted of very fine and interconnected oxides and porosity whereas, at 350 W, they exhibited circular and well-defined secondary grains. These observations were discussed in relation to the magnetron sputtering process and RF power.