2D materials are a general term for a large class of materials, referring to the thickness of the atomic layer whose material size is reduced to the limit in one dimension, and the material size is relatively large in the other two dimensions. The most typical and first experimentally proven two-dimensional material is graphene. In 2004, K. S. Novoselov et al. published an article in Science magazine, which reported that graphene was obtained from highly oriented pyrolytic graphite by mechanical exfoliation and proved its unique and excellent electrical properties. Since then, two-dimensional materials represented by graphene have developed rapidly, and new two-dimensional materials have sprung up. Thanks to the quantum confinement effect in the direction of the thickness of the atomic layer, these two-dimensional materials exhibit different properties from their corresponding three-dimensional structures, and thus have received extensive attention from the scientific community and industry.
In addition to graphene, other two-dimensional materials include: silene, decene, tinene, borene and black phosphorus of single elements, transition metal chalcogenides such as MoS2, WSe2, ReS2, PtSe2, NbSe2, etc. Main group metal chalcogenides such as GaS, InSe, SnS, SnS2, etc., and other two-dimensional materials such as h-BN, CrI3, NiPS3, Bi2O2Se, and the like. These two-dimensional materials have completely different energy band structures and electrical properties, covering materials ranging from superconductors, metals, semi-metals, semiconductors to insulators. At the same time, they also have excellent optical, mechanical, thermal, magnetic and other properties. By building two-dimensional materials with different types, it is possible to construct a more functional material system. Therefore, these materials are expected to be used in high-performance electronic devices, optoelectronic devices, spintronic devices, and energy conversion and storage.
At present, the research on two-dimensional materials in experiments has focused on preparation, characterization, modification and application exploration, and has made great progress. For example, in terms of preparation, mechanical stripping is widely used to prepare two-dimensional material samples for laboratory physical property research and device fabrication; chemical vapor deposition can be used to prepare large-area, high-quality, layer-controlled graphene. And part of the transition metal chalcogenide material, laid the foundation for commercial applications. For the characterization of two-dimensional materials, researchers have established a series of characterization methods such as complementary spectroscopy and electron transport. Modification and modification is also an important aspect of the development of two-dimensional materials. By means of doping, chemical modification, electrostatic regulation, alloying, etc., the defects of the materials themselves can be avoided to the greatest extent and their advantages can be exerted. In terms of applications, the construction of graphene-based high-frequency transistors, the short-channel field-effect transistors and tunneling transistors based on MoS2, and other high-efficiency luminescence and photo-detector implementations have shown great potential of applications for two-dimensional materials.
Although the experimental research on two-dimensional materials has made great progress, the theoretical calculation is based on the development of two-dimensional materials because of the long research cycle, the manpower, the relatively large material resources, and the limitations of experimental techniques. It is a crucial role. The research group mainly uses first-principles calculation to find new-type, two-dimensional materials with application prospects, explore some novel properties of two-dimensional materials, explain the observed phenomena, cooperate with the experimental group, and guide experimental design.
