Fabrication and Analysis Of 2D/3D Heterojunction Between Continuous Few-layer WS2 Film and Si (100)†

Abstract

T he excellent electronic properties of the various two-dimensional (2D) materials have led to new developments for the nanoelectronic devices after discovering of the graphene. Heterostructures created by using 2D and 3D materials are becoming one of the main research area for the nanoelectronic devices in recent years [1]. TMDCs such as WS 2 , MoS 2 , MoSe 2 , and WSe 2 have adjustable bandgaps to be indirect in their bulk form and direct in the monolayer [2]. This feature has potential in various electronic and optical applications for TMDCs [3]. Structurally, WS 2 has a crystal structure consisting of S-W-S sandwich layers and the atoms in the layers are packaged hexagonally [4]. These layers are held together by the weak van der Waals (vdW) forces so WS 2 can easily be converted into a single layer form [5]. Because of these significant features, WS 2 has become a good candidate for the new generation micro and nanoelectronics [6]. Unlike the graphene, the WS 2 has a direct band gap semiconductor with a gap of 2.1 eV in single layer form while as the material passes into a bulk form, the gap is direct in the size of 1.3 eV [7]. The presence of this bandgap made it possible to produce WS 2 transistors with a 10 8 on/off ratio and high sensitivity photo detectors [8].

Vertical van der Waals heterojunction diodes comprising 2D semiconductors on 3D β-Ga2O3

“…WS 2 and WSe 2 are well-established TMDCs that share a trilayer, van der Waals-bonded S/Se-W-S/ Se structure. 17 Their properties have already been incorporated in high-performing optoelectronic devices, field-effect transistors (FETs) and light-emitting diodes (LEDs) and other heterostructures. 18,19,20 Although WS 2 and WSe 2 are similar in structure, their bandgaps and hence band alignments are slightly different: WSe 2 presents a type 2 band alignment with Ga 2 O 3 , whereas WS 2 yields a type 1 alignment, as represented in Fig.…”