Kinetic study of a-Si crystallization induced by an intermetallic compound

The problem under study is concerned with amorphous silicon (a-Si) crystallization which is induced by an intermetallic compound, with this compound chosen to be Al₂Cu, formed by a solid-state reaction between nanolayers of aluminum and copper in a Cu/Al/a-Si multilayer system. In the case of crystallization initiated by the intermetallic compound Al₂Cu, the crystallization temperature of amorphous silicon was found to be ≈ 300°С (upon heating at a rate of 5–10 °C/min), which was significantly higher than in the case of pure Al (≈170°С), but lower as compared to using pure Cu (≈485°С). The higher crystallization temperatures in comparison with aluminium-induced crystallization are assumed to be caused by a decrease in the number of free electrons due to the presence of copper and formation of the Al₂Cu phase. By kinetic modeling, it was revealed that the mechanism of a-Si crystallization induced by the intermetallic compound Al₂Cu was similar to the mechanism of Al-induced crystallization of a-Si in multilayer (Al/a-Si)_n films, i.e the process of a-Si crystallization occurred in two subsequent stages: Cn-X→Fn. Kinetic parameters of silicon crystallization for each reaction step were obtained. The enthalpy of a-Si crystallization initiated by Al₂Cu was estimated to be ΔH = 12.3 ± 0.5 kJ/mol.