层状二硫化钼研究进展

近年来,层状二硫化钼由于其特殊的类石墨烯结构和独特的物理化学性质已成为国内外研究的热点.本文综述了层状二硫化钼的物理结构、价带结构和光学性质;介绍了制备方法,包括生长制备和剥离制备.生长制备的原料包括四硫代钼酸铵((NH4)_2MoS_4)、钼(Mo)和三氧化钼(MoO_3)等.剥离制备包括微机械剥离、液相超声法、锂离子插层法和电化学锂离子插层法等.归纳了层状二硫化钼在场效应晶体管、传感器和存储方面的应用,展望了层状二硫化钼的研究前景.

Recent progress of two-dimensional layered molyb denum disulfide

Recently, two-dimensional (2D) layered molybdenum disulfide (MoS₂) has attracted great attention because of its graphene-like structure and unique physical and chemical properties. In this paper, physical structure, band gap structure, and optical properties of MoS₂ are summarized. MoS₂ is semiconducting and composed of covalently bonded sheets held together by weak van der Waals force. In each MoS₂ layer, a layer of molybdenum (Mo) atoms is sandwiched between two layers of sulfur (S) atoms. There are three types of MoS₂ compounds, including 1T MoS₂, 2H MoS₂, and 3R MoS₂. As the number of layers decreases, the bad gap becomes larger. The bad gap transforms from indirect to direct as MoS₂ is thinned to a monolayer. Changes of band gap show a great potential in photoelectron. Preparation methods of 2D MoS₂ are reviewed, including growth methods and exfoliation methods. Ammonium thiomolybdate (NH₄)₂MoS₄, elemental molybdenum Mo and molybdenum trioxide MoO₃ are used to synthesize 2D MoS₂ by growth methods. (NH₄)₂MoS₄ is dissolved in a solution and then coated on a substrate. (NH₄)₂MoS₄ is decomposed into MoS₂ after annealing at a high temperature. Mo is evaporated onto a substrate, and then sulfurized into MoS₂. MoO₃ is most used to synthesize MoS₂ on different substrates by a chemical vapor deposition or plasma-enhanced chemical vapor deposition. Other precursors like Mo(CO)₆, MoS₂ and MoCl₅ are also used for MoS₂ growth. For the graphene-like structure, monolayer MoS₂ can be exfoliated from bulk MoS₂. Exfoliation methods include micromechanical exfoliation, liquid exfoliation, lithium-based intercalation and electrochemistry lithium-based intercalation. For micromechanical exfoliation, the efficiency is low and the sizes of MoS₂ flakes are small. For liquid exfoliation, it is convenient for operation to obtain mass production, but the concentration of monolayer MoS₂ is low. For lithium-based intercalation, the yield of monolayer MoS₂ is high while it takes a long time and makes 2H MoS₂ transform to 1T MoS₂ in this process. For electrochemistry lithium-based intercalation, this method saves more time and achieves higher monolayer MoS₂ yield, and annealing makes 1T MoS₂ back to 2H MoS₂. The applications of 2D MoS₂ in field-effect transistors, sensors and memory are discussed. On-off ratio field effect transistor based on MoS₂ has field-effect mobility of several hundred cm²·V^-1·^-1 and on/off ratio of 10⁸ theoretically.