In situ investigation of explosive crystallization in a-Ge: Experimental determination of the interface response function using dynamic transmission electron microscopy

Abstract

The crystallization of amorphous semiconductors is a strongly exothermic process. Once initiated the release of latent heat can be sufficient to drive a self-sustaining crystallization front through the material in a manner that has been described as explosive. Here, we perform a quantitative in situ study of explosive crystallization in amorphous germanium using dynamic transmission electron microscopy. Direct observations of the speed of the explosive crystallization front as it evolves along a laser-imprinted temperature gradient are used to experimentally determine the complete interface response function (i.e., the temperature-dependent front propagation speed) for this process, which reaches a peak of 16 m/s. Fitting to the Frenkel-Wilson kinetic law demonstrates that the diffusivity of the material locally/immediately in advance of the explosive crystallization front is inconsistent with those of a liquid phase. This result suggests a modification to the liquid-mediated mechanism commonly used to describe this process that replaces the phase change at the leading amorphous-liquid interface with a change in bonding character (from covalent to metallic) occurring in the hot amorphous material.

Superconducting Polycrystalline Silicon Layer Obtained by Boron Implantation and Nanosecond Laser Annealing

“…2a). Such a signal is representative of explosive recrystallization (ER) during which, a fast and exclusive melt of a-Si occurs before a fast solidification into poly-Si 20 (regime 2, Fig. 2a).…”

Formation of Nanotwin Networks during High-Temperature Crystallization of Amorphous Germanium

“…This is compounded by latent heat deposition released during the exothermic a → c process, which increases the temperature beyond that tipping point. The phenomenon where crystallization is fueled by the intrinsic latent heat release is well known and referred to as explosive crystallization 40 41 42 . For this, however, an increase in temperature should result in growth acceleration by a surge in interface velocity, which is not the case in the temperature regime considered here.…”

“…For this, however, an increase in temperature should result in growth acceleration by a surge in interface velocity, which is not the case in the temperature regime considered here. In all, high nucleation rates due to small critical radii, slow mobilities due to high temperatures, plus high-twinning propensities result in the notoriously fine-grained nanostructures reported for laser-induced Ge crystallization 18 41 42 43 . We have recently proposed a thermodynamically-consistent phase field model to predict these microstructures 22 .…”

Взрывной Переход В Аморфном Микропроводе

“…ВК наблюдалась в аморфных пленочных структурах: полупроводниках [4][5][6], металлах [7,8], диэлектриках [9]. Большую роль при этом играла подложка, в которую осуществлялся основной отвод тепла, выделяющегося при саморазогреве.…”