Atomic‐Scale Structural Dynamics at a‐Si:H/c‐Si Heterointerface During Low‐Temperature Thermal Annealing

Abstract

AbstractThe integrity of the hydrogenated amorphous silicon/crystalline silicon (a‐Si:H/c‐Si) interface is essential for the enhanced performance of a‐Si:H/c‐Si heterojunction‐based devices. However, during annealing processes aimed at passivating silicon dangling bonds, unexpected Si epitaxy and nanotwin formation tend to emerge, even under low‐temperature conditions. Therefore, understanding the influence of such annealing on the a‐Si:H/c‐Si interfacial structure is therefore pivotal for device optimization. In this study, the atomic‐scale structural transformation of the a‐Si:H/c‐Si heterointerface subjected to low‐temperature annealing is delved into. The dynamic evolution of this interface is captured by employing in situ spherical aberration (CS)‐corrected transmission electron microscopy (TEM), molecular dynamics (MD) simulations, and density functional theory (DFT) calculations. The TEM observations indicated that Si epitaxy initiated before Si nanotwin formation, and these nanotwins are inclined to revert to epitaxial structures upon sustained annealing. Through MD and DFT insights, the thermodynamic and kinetic intricacies driving the concerted tri‐layer atomic shift characterizing the Si nanotwin‐to‐epitaxy transition are decoded. The findings shed light on the thermal behavior of a‐Si:H/c‐Si interfaces, offering new perspectives on the thermal management in silicon heterojunction devices.