Van der Waals Epitaxy of Two-Dimensional MoS₂–Graphene Heterostructures in Ultrahigh Vacuum

Abstract

In this work, we demonstrate direct van der Waals epitaxy of MoS2-graphene heterostructures on a semiconducting silicon carbide (SiC) substrate under ultrahigh vacuum conditions. Angle-resolved photoemission spectroscopy (ARPES) measurements show that the electronic structure of free-standing single-layer (SL) MoS2 is retained in these heterostructures due to the weak van der Waals interaction between adjacent materials. The MoS2 synthesis is based on a reactive physical vapor deposition technique involving Mo evaporation and sulfurization in a H2S atmosphere on a template consisting of epitaxially grown graphene on SiC. Using scanning tunneling microscopy, we study the seeding of Mo on this substrate and the evolution from nanoscale MoS2 islands to SL and bilayer (BL) MoS2 sheets during H2S exposure. Our ARPES measurements of SL and BL MoS2 on graphene reveal the coexistence of the Dirac states of graphene and the expected valence band of MoS2 with the band maximum shifted to the corner of the Brillouin zone at K̅ in the SL limit. We confirm the 2D character of these electronic states via a lack of dispersion with photon energy. The growth of epitaxial MoS2-graphene heterostructures on SiC opens new opportunities for further in situ studies of the fundamental properties of these complex materials, as well as perspectives for implementing them in various device schemes to exploit their many promising electronic and optical properties.

Booming Development of Group IV–VI Semiconductors: Fresh Blood of 2D Family

“…Moreover, in‐situ growth of vertical ( Figure 11 a) and lateral (Figure 11b) heterostructures are very important for exploring the novel physical properties, considering that most of the reports on 2D GIVMCs is currently based on the transferred heterojunctions,130, 243, 244 which may harm the electronic properties231, 240 due to the dangling bonds and adsorbates at the interface. In addition, graphene is an ideal template to promote the nucleation and growth of other 2DLMCs crystals for producing functional hybrid structures via CVD method (Figure 11c),198, 204, 207 which may result in the modulation of the electric and optical properties coupled with graphene. The fast growing field calls for more works to fully understand the junction formation and resulted physical properties in 2D GIVMCs crystals.…”

“…Van der Waals (vdW) heterostructures composed of 2D layered materials have been attempted intensively recently due to the novel physical properties covering a wide range of electronic, optical, and optoelectronic systems 198, 199, 200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241, 242. Jo and co‐workers130 synthesized polymorphic 2D tin‐sulfides of either p‐type SnS or n‐type SnS 2 via adjusting hydrogen during the process.…”

Tuning the electronic structure of monolayer graphene/MoS2van der Waals heterostructures via interlayer twist

“…These theoretical and optical investigations have led to a pressing need for a full understanding of the electronic structure of Gr/MoS 2 vdW heterostructures. Very recently, photoemission measurements of Gr/MoS 2 interface have been attempted [24][25][26]. Thus Coy-Diaz et al examined a twisted interface between polycrystalline graphene and a bulk MoS 2 crystal [24,25], while Miwa et al examined the electronic structure of a multidomain epitaxial MoS 2 -graphene heterostructure, which is laterally averaged over different orientations [26].…”

“…Very recently, photoemission measurements of Gr/MoS 2 interface have been attempted [24][25][26]. Thus Coy-Diaz et al examined a twisted interface between polycrystalline graphene and a bulk MoS 2 crystal [24,25], while Miwa et al examined the electronic structure of a multidomain epitaxial MoS 2 -graphene heterostructure, which is laterally averaged over different orientations [26]. In all, a direct experimental investigation of the evolution of the momentumresolved electronic structure with twist angle in Gr/MoS 2 twisted bilayer has, thus far, been lacking.…”

Growth of Transition Metal Dichalcogenides and Directly Modulating Their Properties by Chemical Vapor Deposition

“…Except for combination between TMDs, separately grow TMDs and other layered materials is effective to form heterostructures. MoS2 can be grown on CVD grown h-BN film [107] or graphene [108][109][110][111][112][113] to form vertical heterostructures. Large area heterostructure film is promising in mass scale integration applications including FET arrays, Hall bar arrays, inverters, tunneling devices, etc.…”