Structure and Phase Transformation of Nanocrystalline and Amorphous Alloy Thin Films

Abstract

The systematic study on the structure and morphology of Ag-Si alloy thin films shows nanocrystalline Ag clusters embedded in amorphous Si matrix for samples of different compositions and thicknesses. Ag cluster sizes increase from 2.5 nm to 3.5 nm as annealing temperature increases from room temperature to 500°C, and the cluster densities decrease accordingly from 2.5x10 4/mum2 to 7.6x103/mum 2. This phenomenon can be explained by grain growth and Ostwald ripening in which big clusters grows bigger at the expense of smaller clusters. The Ag clusters remain relatively stable under annealing; HREM images show crystalline structure at 500°C, which is different from Ag clusters supported on other substrates. TEM observation shows that Ag clusters are embedded inside the amorphous Si matrix, which explains their relative stability at high temperatures.