Atomic-Scale Mechanism Study of Medium-Range Order Clusters Evolution and Amorphous Incubation Layer Elimination in Hydrogenated Silicon Thin Films with Realistic Network

Abstract

The medium-range order in plasma-deposited silicon thin films arises from kinetic competition among hydrogen-induced crystallization, dissociative incorporation, hydrogen etching, and surface diffusion, yet the quantitative role of this competition remains unclear. Incorporating results from molecular dynamics and first-principles calculations, a lattice-free continuous random network model is built that employs a kinetic Monte Carlo method driven by event-specific rates, where the Si−Si network evolves through these competing events. The onset height of Schläfli clusters and height-resolved Si−Si radial distribution functions are tracked from 373 K to 623 K. At low temperatures, diffusion and etching dominate, leaving the film amorphous and devoid of Schläfli clusters. With increasing temperature, crystallization and incorporation prevail, and the onset height decays nearly exponentially from 23 Å at 446 K to 1.5 Å at 623 K. At 623 K, the incubation layer vanishes and a structurally uniform interfacial layer forms. This work establishes the temperature-dependent competition between crystallization/incorporation and diffusion/etching as the mechanism controlling medium-range order, provides a unified kinetic framework for the diffusion, etching, and chemical annealing models, and identifies temperature windows in which this competition dictates the resulting nanostructure.