Microstructure of radio frequency sputtered Ag1−xSix alloys

Abstract

A series of thin film Ag1−xSix alloys were fabricated using radio frequency sputter deposition with composite Ag+Si sputter targets and water-cooled and liquid nitrogen–cooled substrate holders. The microstructures of the films were analyzed using x-ray diffraction and transmission electron microscopy. As-deposited films contained fcc Ag and amorphous Si. The Ag grain size decreased as the Si content increased. Films deposited on the liquid nitrogen–cooled substrate holder exhibited grain sizes smaller than films deposited on the water-cooled substrate holder. Despite the negligible Ag and Si mutual solid solubilities, the metastable Ag3Si hcp silver silicide phase was observed in addition to fcc Ag and amorphous Si in a 12 at. % Si alloy deposited on the liquid nitrogen–cooled substrate holder. The Ag3Si phase observed by x-ray diffraction in 5000-Å-thick films was not found in the 250-Å-thick TEM films, suggesting a thickness dependence of stability. During vacuum anneals above 100 °C, the Ag3Si phase partially decomposed.