Highly Scalable, Atomically Thin WSe₂ Grown via Metal–Organic Chemical Vapor Deposition

Abstract

Tungsten diselenide (WSe2) is a two-dimensional material that is of interest for next-generation electronic and optoelectronic devices due to its direct bandgap of 1.65 eV in the monolayer form and excellent transport properties. However, technologies based on this 2D material cannot be realized without a scalable synthesis process. Here, we demonstrate the first scalable synthesis of large-area, mono and few-layer WSe2 via metal-organic chemical vapor deposition using tungsten hexacarbonyl (W(CO)6) and dimethylselenium ((CH3)2Se). In addition to being intrinsically scalable, this technique allows for the precise control of the vapor-phase chemistry, which is unobtainable using more traditional oxide vaporization routes. We show that temperature, pressure, Se:W ratio, and substrate choice have a strong impact on the ensuing atomic layer structure, with optimized conditions yielding >8 μm size domains. Raman spectroscopy, atomic force microscopy (AFM), and cross-sectional transmission electron microscopy (TEM) confirm crystalline monoto-multilayer WSe2 is achievable. Finally, TEM and vertical current/voltage transport provide evidence that a pristine van der Waals gap exists in WSe2/graphene heterostructures.

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

“…CVD‐grown graphene has made great breakthrough in the growth of large‐area graphene 17, 155, 156, 157, 158, 159, 160. Recently, the synthesis of 2DLMs via CVD methods has been illustrated in many reports especially for MoS 2 ,30, 31, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185 which also shows promising applications in electronics and optoelectronics. Up to now, there are several reports on synthesizing 2D GIVMCs nanoflakes via CVD method, which is still at the initial stage.…”

Light–matter interaction in transition metal dichalcogenides and their heterostructures

“…The synthesis of large area -wafer scale and uniform layers of single layer TMDs is approached by bottomup methods such as by chemical vapor deposition (CVD) [109][110][111][112] , metal organic chemical vapor deposition (MOCVD) [113] , physical vapor phase growth (PVG) [114,115] or dip-coating of a precursor and thermolysis crystallization by annealing in sulphur gas [116] . There is great progress and it is possible to grow single layer high quality flakes with up to 300 µm in size covering a cm-sized substrate surface [117] .…”

Layered Two-Dimensional Heterostructures and Their Tunneling Characteristics

“…WSe 2 synthesis is carried out on EG substrates with conditions as previously reported by Eichfeld et al, [53] with the W and Se precursors in this growth being W(CO) 6…”

“…To o er insight in this regard, we turned to low-energy electron microscopy (LEEM), another high-throughput technique that would allow us to investigate the structural and electronic properties of these materials without the complications of device patterning. To begin this investigation, we focused on simple heterostructures involving a single TMD formed on graphene, which also showed interesting vertical transport with CAFM, [5,50,53] and would serve as a baseline for studies of more complex structures.…”