Fabrication of Optoelectronic Devices with Two-dimensional Layered Materials and Their Heterostructures

This thesis focuses on the fabrication of two-dimensional (2D) layered materials-based devices for optoelectronic applications, such as graphene-based modulators, WSe2/MoSe2 heterojunction and WSe2/SnSe2 heterojunction-based photodetectors. The thesis is divided into five parts. The first part gives an overview of the potential applications of 2D layered materials and their heterostructures in the field of optoelectronics. The second part introduces the fundamental properties of 2D layered materials, including graphene, transition metal dichalcogenides, and their van der Waals heterojunctions. The third part discusses the process methods that have been used for fabrication of optoelectronic devices. For example, mechanical exfoliation and chemical vapor deposition methods are used to obtain 2D layered materials, and electron beam lithography, atomic layer deposition and reactive ion etching are the most important methods during the device processing. The fourth part introduces the characterization methods of the fabricated devices. For example, Raman and photoluminescence spectroscopies are used to characterize the 2D layered materials, and Atomic force microscope is used to check the thickness of the exfoliated 2D layered material flakes. The electrical and photocurrent measurements are also presented for characterization of device performance. The fifth part presents the optoelectronic applications of the fabricated devices. First, two different kinds of graphene-based modulators are presented. Then, we demonstrate the WSe2/MoSe2 and WSe2/SnSe2 heterojunctions-based photodetectors with broadband photodetection and high photoresponsivity. Finally, I summarize the whole contents and give the outlook on the applications of the 2D layered materials-based optoelectronics.