Fabrication and characterization of heterostructures with subnanometer thickness

Good quality of heterostructures with subnanometer thickness have been successfully grown for the first time with van der Waals epitaxy. The van der Waals epitaxy can be realized in the materials having no dangling bonds on their clean surfaces, on which epitaxial growth proceeds by the van der Waals force. We have succeeded to grow ultrathin selenium film on a cleaved face of tellurium and ultrathin NbSe 2 film on a cleaved face of 2H-MoS 2 by making full use of the van der Waals epitaxy. Although there exists lattice mismatching as large as 20 % between those materials forming the heterostructure, the grown film has been proved to be good single crystalline one having a lattice constant of its own even in the first atomic layer at the interface.