Multi-scale characterization of hexagonal Si-4H: a hierarchical nanostructured material

TL;DR

This paper provides a multi-scale structural analysis of hexagonal Si-4H, revealing its hierarchical morphology, 2D platelet structure, and potential for optoelectronic applications through detailed imaging and dispersion techniques.

Contribution

It introduces the first detailed hierarchical characterization of Si-4H, identifying its platelet units and demonstrating their flexibility and dispersibility for device design.

Findings

Identified hierarchical structure with platelets as basic units

Demonstrated the 2D, flexible nature of Si-4H platelets

Showed potential for optoelectronic and solar device applications

Abstract

In this work we present a detailed structural characterization of Si-4H, a newly discovered bulk form of hexagonal silicon (Si) with potential optoelectronic applications. Using multi-scale imaging, we reveal a hierarchical structure in the morphology of Si-4H obtained from high-pressure synthesis. We demonstrate discrete structural units, platelets, at an intermediate length-scale between the bulk pellets synthesized at high pressures and the flake-like crystallites inferred in previous studies. Direct observation of the platelets reveals their 2D structure, with planar faces spanning hundreds of nanometers to a few micrometers and thicknesses of only tens of nanometers. We separated and dispersed small packets of quasi-single platelets, which enabled us to analyze the crystalline domains within each grain. With this view, we demonstrate that Si-4H platelets represent the smallest crystalline structural units, which can bend at the single-domain level. Our characterization of the quasi-2D, flexible platelets of hexagonal Si-4H and proof of concept that the platelets can be dispersed and manipulated quite simply demonstrate opportunities to design novel optoelectronic and solar devices.