Three-step, transfer-free growth of MoS₂/WS₂/graphene vertical van der Waals heterostructure

Abstract

Van der Waals heterostructures (vdWHS) provide a unique playground to study fundamental physics and practical applications of two-dimensional (2D) materials. However, most 2D heterostructures are prepared by transfer, hindering their technological implementation. Here, we report the first chemical vapour deposition (CVD) of monolayered MoS2/WS2/graphene vertical vdWHS without transfer step. By atomic force microscopy, photoluminescence, Raman spectroscopy, and secondary ion mass spectroscopy, we confirmed the vertical stacking of three different 2D materials. The use of WS2, graphene, and sapphire as growth substrates allowed us to describe the 2D materials growth process better. We determined that for the synthesis of 2D materials, only the chemical potential of the crystal formation and the substrate-layer adhesion energy are relevant factors. In addition, we used MoS2/WS2/graphene vdWHS to fabricate a photoresponsive memory device, showing the application potential of such heterostacks. Our results clarify the growth mechanisms of 2D materials and pave the way for the growth of more complex van der Waals heterostructures.

Two-Dimensional Crystals as a Buffer Layer for High Work Function Applications: The Case of Monolayer MoO3

“…We emphasize that, among global properties and efficiency of the applied materials, the functional layers should be deeply studied on the nanoscale by electronic structure-sensitive techniques, as this is where potential optimization should be looked for. This approach especially paves the way for designing more complex vdW heterostructures. , …”

“…This approach especially paves the way for designing more complex vdW heterostructures. 32,33 ■ RESULTS AND DISCUSSION Monolayer MoO 3 �Morphological Characterization. We synthesized monolayer MoO 3 directly on HOPG in UHV through thermal evaporation of MoO 3 powder at elevated substrate temperatures, as described in our previous work.…”

Selective Growth of van der Waals Heterostructures Enabled by Electron-Beam Irradiation

“…The growths were conducted for 15 min in an Ar atmosphere. The detailed MoS 2 and WS 2 growth procedures were presented elsewhere. , …”

“…The detailed MoS 2 and WS 2 growth procedures were presented elsewhere. 45,46 MOCVD growth of MoS 2 was conducted in a 4 in. tube furnace using molybdenum hexacarbonyl and diethyl sulfide as precursors under a hydrogen and argon atmosphere.…”

Realization of low potential barrier in MoS2/rGO heterojunction with enhanced electrical conductivity for thin film thermoelectric applications

“…the contribution of electronic and lattice thermal conductivity, respectively [1]. Recently two-dimensional (2D) transition metal dichalcogenides (TMDCs) materials have paid great interest in the field of TE due to high mobility, low k l and high S. Among TMDCs, MoS 2 is an emerging material in the field of thermoelectric due to its intrinsic properties such as van der Waals (vdWs) interaction between the layers, anisotropy and tunable bandgap of 1.2 to 1.8 eV for bulk to monolayer, respectively [2]. The density of states (DOS) near Fermi level could be increased in low-dimensional materials which will enhance phonon scattering.…”