Role of Cu2O surface terminations on interface conductivity with graphene

Abstract

Two-dimensional materials and their interfaces with functional oxides have increasing applications in optoelectronic devices. Cu2O is an important functional oxide and efficient charge transport across the Cu2O/contact material interface is a significant bottleneck in the development of efficient optoelectronic devices. Here, we investigate the electronic properties of graphene, a transparent contact material, interface with intrinsic (100) Cu2O thin films using first principles calculations. From the graphene-Cu2O heterojunction interface, we observe that despite the Cu2O surface termination and electronegativity order of the atoms involved, the physisorbed graphene layer is always electron depleted. The graphene heterojunction with the reconstructed Copper terminated surface shows a covalent character, a smaller tunnel barrier and blocking Schottky potential of 0.19 eV for holes. In contrast, the reconstructed oxygen terminated structure shows an ionic character, a significantly taller tunnel barrier and a transparent ohmic contact for holes. These results show that graphene is an attractive transparent contact material for Cu2O based hole transport layers in photovoltaics, chemical and photon sensing, and energy storage.