Phase diagram study of the formation and crystallization of Ge-metal amorphous alloy films

Abstract

The Ge-Au and Ge-Ag alloy films were deposited in vacuum at room temperature and then systematically observed in the TEM. The maximum metallic concentrations in the alloy films,Cmax, which form the stable amorphous alloy phases of germanium with gold and silver, were obtained. The annealed crystallization temperatureTc, which falls with increasing metallic content in these films was also found. The structures of these films and their annealed specimens were also studied. There are various factors which influence the formation of amorphous alloy films deposited in vacuum for Ge-metal systems. A new formula forCmax has been derived. The annealed crystallization character has been explained by means of the variation of the free energy and the activation energy of crystallization. The activation energy of crystallization,Ea, can be obtained from the data values ofTc. For Ge-Au films,Ea (Au)=Eao/(−18.66CAu2+16.83CAu+1)±3.3 (kcal mol−1); for Ge-Ag films,Ea (Ag)=Eao/(−2.754CAg2+3.815CAg+ 1)±2.6 (kcal mol−1). In order to explain all these results, two kinds of phase diagram for the alloy films have been introduced. One is the three-dimensional relationship diagrams of phase formation in semiconductor-metallic alloy films; it was introduced to explain the influencing factors. The other is the three-dimensional phase diagrams of annealed semiconductor-metallic films systems. From this diagram all the phase transitions can be found.