Compliant Substrate Epitaxy and Manufacturing of 2D Materials

Semiconductor transition metal dichalcogenide monolayers offer a range of interesting material properties.  However, reliably transferring a monolayer from a bulk source, while minimizing cracks, has proved difficult.  In order to address this problem, a theory of compliant substrate epitaxy has been developed and we are currently expanding upon earlier work. This process  works by depositing a metallic film on a bulk sample of the transition metal dichalcogenide.  The metallic film strains the first layer of the bulk material, but the strain field doesn’t substantially propagate through the bulk of the sample.  This breaks the symmetry between the first monolayer and the remaining bulk material, allowing a single monolayer to be removed.

In addition to further developing the theory, we are also applying this process towards the discovery of a reliable and efficient manufacturing process in collaboration with other members of electronic materials program at LBL and the mechanical engineering department at UC Berkeley.  For both of these goals, we are using molecular dynamics and density functional theory to model the exfoliation process, and determining the optimal film material and thickness, that should be used to remove a specific transition metal dichalcogenide monolayer.