Al thin film: The effect of substrate type on Al film formation and morphology

In this work aluminium (Al) films were deposited on different substrates, and their phase, microstructure and film growth process were tracked. Three types of substrates were explored to determine the influence of the substrate on the film growth process. It was determined that the growth mechanism of Al on the metal substrate was totally different from that on metalloids and glass. The Al film grown on metal substrate had a cross-grained structure, while films formed on glass had a fine-grained structure. Film grown on metalloids fell between the two. It was found that these differences in microstructure affected the film's optical properties. Films grown on silicon and glass were very reflective while film grown on the metallic substrate scattered light. It was determined that nucleation of the film deposited on the metallic substrate began when the film thickness exceeded 50 nm. Further increasing thickness triggered grain growth, and the formation of crystallites up to 40 nm occurred when film thickness was 150 nm. It was observed that grain growth was more favorable on metallic substrates, and the lowest grain growth was observed on the glass substrate.