Phase transformation between Cu(In,Sn)2 and Cu2(In,Sn) compounds formed on single crystalline Cu substrate during solid state aging

Abstract

Interfacial reactions between eutectic SnIn and single crystalline Cu during solid-state aging at low temperature were investigated systematically. Three types of phase transformations between Cu(In,Sn)2 layer and Cu2(In,Sn) layer were observed, which are Cu(In,Sn)2 grows and Cu2(In,Sn) consumes at 40 °C, Cu(In,Sn)2 and Cu2(In,Sn) grow simultaneously at 60 °C, as well as Cu(In,Sn)2 consumes and Cu2(In,Sn) grows at 80 and 100 °C. According to physicochemical approach, the chemical reactions at Cu/Cu2(In,Sn)/Cu(In,Sn)2/SnIn interfaces were discussed in detail. It was concluded that the diffusion ability of Cu and In atoms dominated different phase transformations. When diffusion constants k1In2 > 8/3k1Cu2 Cu(In,Sn)2 will grow, and if k1Cu2 ≫ k1In2 Cu2(In,Sn) will grow. Both Cu(In,Sn)2 and Cu2(In,Sn) can grow in the condition of k1In2 ≈ k1Cu2. The values of k1Cu2 and k1In2 at different temperatures on (100)Cu and (111)Cu substrate were also calculated or estimated by analyzing the growth kinetics of the compound layers.