The influence of substrate temperature, substrate material and heat treatment on the micro structure of Ag/Si nanocomposite films prepared by r.f. co-sputtering

Nanocomposite films consisting of silver and silicon were manufactured by r.f. co-sputtering deposition. The influence of substrate temperatures varying from 20 to 200 °C and different substrate materials such as cleaved NaCl crystals, C-coated Cu grids and (100) Si single-crystal wafers was investigated. Subsequent heat treatment at different temperatures ranging from 500 to 800 °C and its effect on the microstructure of the deposited films was also investigated by using a combination of differential scanning calorimetry, X-ray diffractometry, scanning electron microscopy, conventional transmission electron microscopy and high-resolution electron microscopy. The typical microstructure of the as-deposited film consisted of nanosized Ag particles embedded in an amorphous Si matrix. The crystallization temperature of the amorphous Si matrix was reduced from 550 to 490 °C with increasing Ag content in the films. The microstructure of the annealed Ag/Si film after crystallization consists of Si crystallites with sizes from several nanometres to hundreds of nanometres and Ag particles with average sizes from 12 nm (600 °C) to 28 nm (800 °C). Surface segregation of silver was also observed for the annealing temperatures of 600 °C and above. We suggest a possible explanation for the silver-induced lowering of the amorphous Si matrix crystallization temperature.