The Effect of Twin Grain Boundary Tuned by Temperature on the Electrical Transport Properties of Monolayer MoS2

Abstract

Theoretical calculation and experimental measurement have shown that twin grain boundary (GB) of molybdenum disulphide (MoS 2 ) exhibits extraordinary effects on transport properties. Precise transport measurements need to verify the transport mechanism of twin GB in MoS 2 . Here, monolayer molybdenum disulphide with a twin grain boundary was grown in our developed low-pressure chemical vapor deposition (CVD) system, and we investigated how the twin GB affects the electrical transport properties of MoS 2 by temperature-dependent transport studies. At low temperature, the twin GB can increase the in-plane electrical conductivity of MoS 2 and the transport exhibits variable-range hopping (VRH), while at high temperature, the twin GB impedes the electrical transport of MoS 2 and the transport exhibits nearest-neighbor hopping (NNH). Our results elucidate carrier transport mechanism of twin GB and give an important indication of twin GB in tailoring the electronic properties of MoS 2 for its applications in next-generation electronics and optoelectronic devices.

Epitaxial Growth of Two-Dimensional Layered Transition Metal Dichalcogenides

“…Due to the broken inversion symmetry in TMDs, when domains of opposite orientation coalesce, an anti-phase boundary (APB) forms, also referred to as an inversion grain boundary. The APBs have a metallic character which is detrimental to electronic properties (48)(49)(50)(51) and is also problematic for studies of valley-related physics. TMD domains should ideally exhibit the same orientation and alignment thereby enabling them to seamlessly coalesce.…”

Wafer-Scale Epitaxial Growth of Unidirectional WS2 Monolayers on Sapphire

“…Inversion domain boundaries (IDBs), which form upon coalescence of 0°and 60°domains, have a metallic character that introduces conducting channels in the semiconductor monolayer. 16 IDBs are further problematic for observation of spin and valley polarization which rely on transitions that occur at the K and −K points in the Brillouin zone. 17 The presence of 0°and 60°domains is readily apparent as oppositely oriented triangles for isolated domains formed on c-plane sapphire as reported for MoS 2 grown by PVT 15,18 and WSe 2 grown by MOCVD.…”

“…In monolayer WS 2 , as well as in other TMD materials, ⟨100⟩ and ⟨010⟩ are not equivalent directions, and domains with opposite directions are referred to as 0° and 60° (or 180°) rotated domains, antiphase domains, or inversion domains. Inversion domain boundaries (IDBs), which form upon coalescence of 0° and 60° domains, have a metallic character that introduces conducting channels in the semiconductor monolayer . IDBs are further problematic for observation of spin and valley polarization which rely on transitions that occur at the K and −K points in the Brillouin zone .…”

Defect-Controlled Nucleation and Orientation of WSe2 on hBN: A Route to Single-Crystal Epitaxial Monolayers

“…The epitaxial growth of TMDs has been further developed into a wafer-scale process via the controlled nucleation and coalescence of a high density of islands into a continuous film on c-plane sapphire . However, inversion domain boundaries (IDBs) (also referred to as mirror twin grain boundaries) were still observed in these films resulting from a merging of a mixture of 0° and 180° oriented domains. ,,, IDBs have been predicted and experimentally demonstrated to exhibit metallic character and, consequently, can serve as conducting channels within the monolayer that negatively impact both electrical and optical properties. − In addition, non-uniformities in the optical and transport properties of these TMD films arise from steps and surface dangling bonds at the interface between the 2D film and 3D substrate. ,, All of these factors negatively impact the properties of coalesced monolayer films and also promote undesirable multilayer growth.…”