Nano-patterned honeycomb structure of monolayer copper selenide on Cu(111)

•Fabricating a well-defined honeycomb structure of CuSe in single atomic layer.•Observing and interpreting the unusual linear Moiré pattern of CuSe layers.•Revealing a narrow band gap by scanning tunneling spectroscopy. Transition metal dichalcogenides generally have three atomic layers forming a buckled honeycomb structure as a covalent sheet. The van der Waals force is the key interaction between these sheets. In our work, we have fabricated a single layered copper selenide structure by employing molecular beam epitaxy method. The selenium and copper atoms form a Moiré pattern with respect to the substrate Cu(111). Combined with density functional theory calculation, the narrow band gap of these structures is investigated in detail.