Structural transformations in a-Ge alloy films

Structural transformations have been studied in amorphous Ge and its alloys with Al, Cu, and Feusing differential thermal analysis (DTA), electron-microscopy, and electrical resistance measurements. The a-Ge-metal alloy films are homogeneous “single” phase films and there is no segregation or clustering of the metal atoms in the as-deposited films. The temperature (Tc) and the heat of transformation (Hc) associated with the amorphous → crystalline transformation for a-Ge are found to be 818 K and 2.60 kcal/mol, respectively. In the case of Ge-metal alloy films, Tc and Hc decrease with increasing metal concentration with the exception of Al in which Tc first increases up to 5 at% Al concentration and then decreases. The amorphous → crystalline transformation in the alloy films occurs by segregation of the metal phase (for Cu and Fe) and/or eutectic formation (for Al).