Origins of stress development during metal-induced crystallization and layer exchange: Annealing amorphous Ge/crystalline Al bilayers

The realtime evolution of stress during metal-induced crystallization (MIC) in amorphous Ge/crystalline Al bilayers was explored by an in situ X-ray diffraction technique in the temperature range of room temperature to 250 °C. The realtime stress developments, in combination with ex situ microstructural and thermal characterizations, revealed complex, distinct correlations of, on the one hand, stress generation and stress relaxation, and, on the other hand, microstructural evolution during the MIC process. MIC in this system is revealed to proceed by rapid crystallization of amorphous Ge at 150 °C and subsequent growth of the crystallized Ge nano-grains at temperatures between 150 °C and 250 °C, in association with a gradual exchange of the positions of the Al and crystallized Ge sublayers. The development of the microstructure and the state of residual stress was interpreted in terms of acting driving forces and operating mechanisms.