二维材料异质结的可控制备及应用

Controllable synthesis of two dimensional heterostructures and their application

二维材料异质结是由石墨烯、六方氮化硼、过渡金属二硫族化合物、黑磷等二维材料通过面内拼接或层间堆叠形成的,并由此可分为二维材料面内异质结和垂直异质结.二维材料面内异质结可以实现区域内载流子的特殊传输行为;而垂直异质结中的层间量子耦合效应能够导致新颖的物理特性,通过调节异质结构界面可调制器件的电学及光学性能.目前,随着电子器件、光电器件等对集成性、功能性的要求不断提高,二维材料异质结越来越多地受到研究者的关注,实现二维材料异质结结构(包括界面)的有效调控是构筑高性能、高集成器件的前提.本文主要对比各类二维材料异质结的制备方法,介绍主流的几类二维材料异质结基电子器件和光电器件的结构、工作原理和性能,展望有前景的新型制备方法,并指出二维材料异质结在实际应用中面临的挑战.

Since the successful exfoliation of graphene in 2004, many attentions have been paid to two-dimensional（2D） materials, which include graphene, h-BN, transition metal dichalcogenides（TMDCs）, black phosphorus（BP） and so on. Although these materials have shown unique characteristics, there are numerous challenges in this emerging field. For example, charge trap between the substrate and the 2D materials seriously influences their excellent electrical properties; some 2D materials are unstable while exposed in air, which will lead to their degradation. To have an intensive study of the basic properties of 2D materials and broaden their field of application, researchers pay attentions to the heterostructures of these materials, which consist of vertically stacked or laterally pieced 2D materials, including graphene/h-BN, TMDCs/h-BN, TMDCs/graphene, and TMDCs/TMDCs heterostructures, et al. For vertical heterostructures, graphene/hBN vertical heterostructures mainly take advantage of h-BN to decrease the charge trap between insulating layer and graphene, thus to increase the carrier mobility in graphene. TMDCs/graphene vertical heterostructures mainly combine the good photo responsivity of TMDCs with the high conductivity of graphene, which can be utilized for high performance optoelectronics. TMDCs/TMDCs vertical heterostructures mainly combine the band structures of two different materials to control the carrier transport behavior, thus realizing excellent carrier storage or high performance photo responsivity. Lateral heterostructures are only suitable for materials with low lattice mismatch, and they are usually used for studying the carrier transport behavior between the interfaces of materials. Along with the increasing requirements on integration and multifunction, 2D heterostructures-based electronic and optoelectronic devices are paid much more attention to. Controllable synthesis of 2D heterostructures is the precondition of constructions of high-performance and highly-integrated devices. This review first introduces the preparation methods of 2D materials, including exfoliation, molecular beam epitaxy（MBE） and chemical vapor deposition（CVD）. Exfoliation method mainly pieces the exfoliated materials together to form heterostructures with the help of polymer. MBE can overcome the difficulties of the transfer process in exfoliation, however they are not suitable for large scale preparation. Compared with exfoliation and MBE, CVD has less restrictions on the substrate, as well as a simple preparation process with lower cost and higher quality of the as-prepared materials. 2D heterostructures can be prepared by the combination of exfoliation and CVD, or CVD process only. Then, considering the problem of the interface contamination in these preparation methods proposed at present, we put forward a liquid metal strategy in the controllable preparation of 2D heterostructures. Furthermore, we introduce the construction and performance of 2D-heterostructures-based electronic and optical devices. The opportunities and challenges in the preparation and application of 2D heterostructures are also discussed.