Questioning van der Waals Epitaxy of Non-Layered Materials on Mica: The Case of ScN

TL;DR

This study demonstrates that the growth of non-layered ScN films on mica occurs via conventional epitaxy, challenging the assumption that van der Waals epitaxy is applicable in such cases, and emphasizes the need for explicit verification.

Contribution

The paper provides experimental evidence that non-layered materials like ScN grow by conventional epitaxy on mica, questioning prior claims of van der Waals epitaxy in similar systems.

Findings

Epitaxial relationship identified as [-101](111)ScN||[010](001)mica

Strain buildup and relaxation mechanisms observed in the films

Conventional epitaxy is the default for non-layered materials on mica

Abstract

Growing stress-free epitaxial films by van der Waals epitaxy (vdWE) is of interest for realizing flexible optoelectronics and energy devices from freestanding epilayers. However, vdWE of non-layered materials is often presumed or claimed on layered substrates such as mica with inadequate experimental evidence. Here, we demonstrate that the growth of single-domain rocksalt ScN(111) films by sputter deposition on fluorophlogopite mica(001) occurs by conventional epitaxy. X-ray diffraction and electron microscopy reveal the film/substrate epitaxial relationship to be [-101](111)ScN||[010](001)mica. Our results indicating strain buildup seen from the dependence of (111) interplanar spacings, and strain relaxation by dislocation generation, question prior claims of vdWE of non-layered metal nitrides on mica. Our findings show that conventional epitaxy should be the default assumption for non-layered materials unless conditions for vdWE are explicitly established.