Gradual Band Evolution at the Electron-Correlated Interface in a Laterally Hetero-Epitaxial Two-Dimensional Heterostructure

As a fundamental characteristic, interfacial band evolution exerts a profound impact on the performance of heterostructures, especially the two-dimensional (2D) lateral heterostructure, which is anticipated with its excellent interfacial properties. Despite intensive reports on semiconductors, studies on 2D electron-correlated heterostructures, which hold big expectations for quantum devices, remain in their early stages on limited materials, hindered by the lack of a controllable fabrication strategy. Here, we report the laterally epitaxial fabrication of the 1T-NbSe2/1T-VSe2 heterostructure and the visualization of the band evolution at its electron-correlated interface. With designed parameters, the 2D VSe2 was successfully grown adjacent to the presynthesized 1T-NbSe2. Atomic-resolution characterizations reveal a well-aligned atomic lattice at the interface. A continuous band profile, particularly the gentle interfacial evolution of the Mott-Hubbard bands, was visualized at the interface, showing the gradual band bending of the upper Hubbard band (∼0.026 eV) and a shrinkage of the Mott-Hubbard gap from 0.124 eV with a decay length of ∼2.4 nm. Our work offers an essential strategy for the fabrication and visualization of 2D electron-correlated heterostructures, laying the groundwork for their fundamental study and future applications.