Synthesis and doping modification of ultrathin WSe2/WS2 heterostructure

Two-dimensional material such as graphene is reported to be outstanding example with remarkable properties, including surprisingly high carrier mobility, extraordinary thermal conductivity and great optical transmittance. However, the limitation of graphene urge us focus on ultrathin layered semiconductors made by transition metal dichalcogenides (TMDCs) such as WS₂ and WSe₂. It possesses outstanding optical and optoelectronics properties. Apart from making pure single crystal, manufacturing of lateral heterostructure with two different TMDC semiconductors is another promising way to exploring the full potential of these layered materials. This thesis report concludes the development history of two dimensional materials from the discovery of graphene, the basic knowledge gap of TMDC to the research of TMDC heterostructure. After that, in this report, a noval single-step chemical vapor deposition (CVD) method for epitaxial growth and selective substitution of lateral WSe₂/WS₂ heterostructures with its growth mechanism are presented. For characterization of resulting heterostructure, Raman, photoluminescence mapping and atomic force microscopy (AFM) were obtained to prove that it is atomically thin lateral heterostructure. Furthermore, detailed Photoluminence (PL) characterisation and Scanning photoelectron microscopy (SPEM) mapping are utilized to study on bonding energy which is direct related to the band shifting and doping module. Electrical characterisation on fabricated device is then report to illustrate the performance of this heterostructure flake. Those studies aims at providing basis of understanding of new single-step synthesis method and the variety of properties of formed heterostructure.