Synthesis of functional nitride membranes using sacrificial water-soluble BaO layers

TL;DR

This paper introduces a novel water-soluble BaO sacrificial layer method for fabricating high-quality, freestanding transition metal nitride membranes, enabling new possibilities for heterostructure integration and device applications.

Contribution

It demonstrates the use of BaO as a universal sacrificial layer for creating crystalline TMN membranes, overcoming lattice mismatch challenges.

Findings

Successful fabrication of millimeter-sized CrN membranes

Direct atomic structure observation of membranes

Correlation of electronic states with transport properties

Abstract

Transition metal nitrides (TMNs) exhibit fascinating physical properties that hold great potential in future device applications. To stack two-dimensional TMNs with other functional materials that have dissimilar orientations and symmetries requires to separate epitaxial TMNs from the growth substrates. However, the lattice constants of TMNs are not compatible with those of most sacrificial layers, leading to a great challenge to fabricate high-quality single crystalline TMN membranes. In this letter, we report the application of a water-soluble BaO sacrificial layer as a general approach to create freestanding TMN membranes. Taken CrN as an example, the relatively small lattice mismatch and identical cubic structure between BaO and CrN ensure the growth of heterostructures. Millimeter-size CrN membrane allows us to directly observe the planar-view of atomic structure and to correlate its electronic state with intrinsic transport properties. Our work provides the opportunity to fabricate freestanding TMN membranes and the ability to transfer them to arbitrary substrates. The integration of TMN membranes with other materials will stimulate further studies in the emergent phenomena at heterointerfaces.