On Properties of Boundaries and Electron Conductivity in Mesoscopic Polycrystalline Silicon Films for Memory Devices

TL;DR

This paper investigates the structural properties of grain boundaries in polycrystalline silicon films and their impact on electron localization and conductance, combining molecular dynamics and Anderson localization models.

Contribution

It introduces a combined molecular dynamics and Anderson localization approach to analyze boundary structures and electron transport in polycrystalline silicon films.

Findings

Grain boundary structures satisfy thermodynamical criteria.

Crossover of localization length correlates with insulator-conductor transition.

Conductance properties change significantly at the transition point.

Abstract

We present the results of molecular dynamics modeling on the structural properties of grain boundaries (GB) in thin polycrystalline films. The transition from crystalline boundaries with low mismatch angle to amorphous boundaries is investigated. It is shown that the structures of the GBs satisfy a thermodynamical criterion. The potential energy of silicon atoms is closely related with a geometrical quantity -- tetragonality of their coordination with their nearest neighbors. A crossover of the length of localization is observed. To analyze the crossover of the length of localization of the single-electron states and properties of conductance of the thin polycrystalline film at low temperature, we use a two-dimensional Anderson localization model, with the random one-site electron charging energy for a single grain (dot), random non-diagonal matrix elements, and random number of connections between the neighboring grains. The results on the crossover behavior of localization length of the single-electron states and characteristic properties of conductance are presented in the region of parameters where the transition from an insulator to a conductor regimes takes place.