Metal-semiconductor ohmic contacts are required to reduce the energy dissipation for two-dimensional (2D) electronic devices, and phase engineering of 2D transition-metal dichalcogenides (TMDCs) is a promising approach for building ohmic contacts. Here, 2D in-plane 1T′-2H MoTe₂ homojunctions were prepared by direct epitaxy via vapor deposition. The interface properties of in-plane 1T′-2H MoTe₂ homojunction were investigated in detail by combining experiments, calculations and theories. The ohmic contact properties of 1T′-2H MoTe₂ homojunction were proved according to Kelvin force probe microscopy and density functional theory calculations. The charge carriers robust transport in in-plane 1T′-2H MoTe₂ homojunction without Fermi-level pinning can be well described by Poisson equation and band alignment. These results indicate that phase engineering of 2D TMDCs is promising to construct ohmic contacts for device applications.

As a new type of two-dimensional (2D) materials, monoelemental 2D materials have the atomic structure similar to graphene, and their excellent optical and electronic properties have potential applications in many fields. To date, many studies based on monoelemental 2D materials have been reported, and excellent performance has been demonstrated in various fields. The monoelemental 2D materials that have been reported so far are mainly distributed in the group IIIA, IVA, VA, and VIA. Because of their structural similarities to graphene, they are commonly referred to as "Xenes." Here, we have comprehensively reviewed the research progress of monoelemental 2D materials. In this review, we explore the structure, properties, and practical applications of these monoelemental 2D materials. First, the classification, structural features, optical properties, electronic characteristics, and regulating mechanism of these monoelemental 2D materials are introduced. Then, the practical application and research progress of monoelemental 2D materials in various fields are reviewed comprehensively, especially including photoelectric catalysis, solar cells, and other energy fields. This review will give readers a more all-sided understanding of monoelemental 2D materials and have some guiding significance for their further development.