Atomically flat two-dimensional silicon crystals with versatile electronic properties

TL;DR

This paper reports the discovery of novel atomically flat two-dimensional silicon crystals with tunable electronic properties, achieved through a systematic ab initio search, potentially advancing silicon-based 2D electronic devices.

Contribution

It introduces a new systematic ab initio approach to identify 2D silicon crystals with unique structures and electronic properties not previously explored.

Findings

New 2D Si structures with flat surfaces and distorted hexagonal networks

Electronic properties range from semimetal to semiconductor with various energy gaps

Surface oxidation and thickness control enable tuning of electronic behavior

Abstract

Silicon (Si) is one of the most extensively studied materials owing to its significance to semiconductor science and technology. While efforts to find a new three-dimensional (3D) Si crystal with unusual properties have made some progress, its two-dimensional (2D) phases have not yet been explored as much. Here, based on a newly developed systematic $ab$ $initio$ materials searching strategy, we report a series of novel 2D Si crystals with unprecedented structural and electronic properties. The new structures exhibit perfectly planar outermost surface layers of a distorted hexagonal network with their thicknesses varying with the atomic arrangement inside. Dramatic changes in electronic properties ranging from semimetal to semiconducting with indirect energy gaps and even to one with direct energy gaps are realized by varying thickness as well as by surface oxidation. Our predicted 2D Si crystals with flat surfaces and tunable electronic properties will shed light on the development of silicon-based 2D electronics technology.