Scalable transparent conductive thin films with electronically passive interfaces for direct chemical vapor deposition of 2D materials

Abstract

We present a novel transparent conductive support structure for two-dimensional (2D) materials that provides an electronically passive 2D/3D interface while also enabling facile interfacial charge transport. This structure, which comprises an evaporated nanocrystalline carbon (nc-C) film beneath an atomic layer deposited alumina (ALD AlOx) layer, is thermally stable and allows direct chemical vapor deposition (CVD) of 2D materials onto the surface. When the nc-C/AlOx is deposited onto a 270 nm SiO2 layer on Si, strong optical contrast for monolayer flakes is retained. Raman spectroscopy reveals good crystal quality for MoS2 and we observe a ten-fold photoluminescence intensity enhancement compared to flakes on conventional Si/SiO2. Tunneling across the ultrathin AlOx enables interfacial charge injection, which we demonstrate by artifact-free scanning electron microscopy and photoemission electron microscopy. Thus, this combination of scalable fabrication and electronic conductivity across a weakly interacting 2D/3D interface opens up new application and characterization opportunities for 2D materials.