Metal-mediated crystallization of amorphous germanium in germanium-silver layered systems

Abstract

Abstract The crystallization behaviour of amorphous Ge (a-Ge) in a-Ge/Ag/a-Ge trilayer and a-Ge/Ag multilayer systems has been investigated using in situ transmission electron microscopy (TEM) and differential scanning calorimetry. The crystallization temperature of a-Ge in these systems is 240–270°C, about 250°C lower than that found in pure a-Ge. During the reaction, in situ cross-section TEM showed that Ag grains separate the a-Ge matrix and the crystallized Ge (c-Ge) grains, and that the Ag grains migrate towards the a-Ge region, leaving the c-Ge phase behind. Our in situ atomic resolution TEM also revealed that the lattice points of the migrating Ag grains are stationary. These observations indicate that the Ge atoms diffuse through the Ag grains for the growth of the c-Ge phase, whereas the migration of the Ag grains is caused by the reverse self-diffusion of the Ag atoms. The mechanism is essentially identical to that in other metal-mediated crystallization reactions (e.g. Al-Si, Ag-Si). The observ...