Low Energy Ion-Induced Crystallization of Ge in c-Al/a-Ge Bilayer Thin Films at Low Temperatures of ∼125 °C

Abstract

The fabrication of polycrystalline Ge films at relatively low temperatures is of great importance for their applications in advanced microelectronic and solar cell devices. In this paper, we present the crystallization of Ge in a c-Al/a-Ge bilayer system at a temperature of 125 °C (lowest ever) using low energy ion beam irradiation followed by post-thermal annealing. The c-Al/a-Ge bilayer thin films are irradiated with 500 keV Kr + and Xe + ions at different fluences and then postannealed at a fixed temperature of 200 °C. The postannealing of the samples at a fixed temperature of 200 °C leads to the formation of polycrystalline Ge, and the crystallinity is observed to increase with increasing ion fluence. The crystallinity is found to be better in the samples irradiated by Xe + ions as compared to the Kr + ions. It is also observed that the thermal annealing of ion-irradiated samples yields better crystallinity than that of the samples that are annealed without irradiation. A temperature-dependent Raman measurement on samples irradiated with a fluence of 1 × 10 16 ions cm −2 reveals the crystallization of Ge at 125 °C. The concepts of layer exchange and irradiation-enhanced kinetics are invoked to explain the crystallization of Ge via different characterization techniques and by using the transport of ions in matter computer simulation code. The presented paper demonstrates the development of polycrystalline Ge at a relatively low temperature using a unique technique of ion irradiation, which may be realized for high performance advanced devices in the future.

Grain-Boundary-Aligned Ge Thin Films Formed by Au-Induced Lateral Crystallization with a Multilayer Structure

“…Similar to Si, the MILC of Ge has also been investigated using several metals, such as Ni, − Co, , Pd, , Cu, , Sn, and Au . The temperature required for the MILC of Ge was lower than that for Si, which makes it promising for the realization of flexible electronics using plastic substrates. , However, the MILC region was composed of tiny crystal grains. ,, This is a challenge unique to polycrystalline Ge layers that is also common to other crystallization methods, such as solid-phase crystallization, − laser annealing, − chemical vapor deposition, , ion-induced crystallization, , and joule-heating induced crystallization. , …”