Anisotropic electronic phase transition in CrN epitaxial thin films

TL;DR

This study demonstrates how anisotropic epitaxial strain in CrN thin films can induce a transition from metallic to semiconducting states, highlighting the role of crystallographic orientation in electronic phase transitions of correlated materials.

Contribution

It reveals the anisotropic strain-driven electronic phase transition in CrN epitaxial films, a novel approach to modulate electronic states in transition metal nitrides.

Findings

CrN films on (110)-oriented NGO are metallic

CrN films on (010)-oriented NGO are semiconducting

Anisotropic strain modulates the bandgap and induces metal-insulator transition

Abstract

Electronic phase transition in strongly correlated materials is extremely sensitive to the dimensionality and crystallographic orientations. Transition metal nitrides (TMNs) are seldom investigated due to the difficulty in fabricating the high-quality and stoichiometric single crystals. In this letter, we report the epitaxial growth and electronic properties of CrN films on different-oriented NdGaO3 (NGO) substrates. Astonishingly, the CrN films grown on (110)-oriented NGO substrates maintain a metallic phase, whereas the CrN films grown on (010)-oriented NGO substrates are semiconducting. We attribute the unconventional electronic transition in the CrN films to the strongly correlation with epitaxial strain. The effective modulation of bandgap by the anisotropic strain triggers the metal-to-insulator transition consequently. This work provides a convenient approach to modify the electronic ground states of functional materials using anisotropic strain and further stimulates the investigations of TMNs.