Strain Modulation of the Out-of-Plane Conductance in Two-Dimensional Material Heterostructures

Layered two-dimensional material (2DM) heterostructures offer anisotropic physical properties that can be tailored via layer assembly without the epitaxial constraints of the bulk. In this work, we analyze the strain modulation of the interlayer current for a variety of nanometer-thick crystalline heterostructures formed with 2DMs, facilitated by their weak mechanical bonding. Descriptions of the tunneling and thermionic emission transport regimes are analyzed using density functional theory and quantum transport calculation in terms of their composition (graphene, boron nitride and transition metal dichalcogenides) and junction length. We develop a model to rationalize these phenomena in terms of the physical properties of the heterostructure constituents (e.g. tunneling rates, density of states, band gap, and Schottky barrier heights). We find piezoresistive gauges in these easily formed systems is comparable to those found in ultraclean bulk systems. Hence, the results of this work show that 2DM heterostructures can expand the repertoire of functional materials and may find applications in sensor technology.