Abstract
Two-dimensional (2D) van der Waal (vdW) heterostructures composed of vertically-stacked multiple transition metal dichalcogenides (TMDs) such as molybdenum disulfide (MoS2) and tungsten disulfide (WS2) are envisioned to present unprecedented materials properties unobtainable from any other material systems. Conventional fabrications of these hybrid materials have relied on the low-yield manual exfoliation and stacking of individual 2D TMD layers, which remain impractical for scaled-up applications. Attempts to chemically synthesize these materials have been recently pursued, which are presently limited to randomly and scarcely grown 2D layers with uncontrolled layer numbers on very small areas. Here, we report the chemical vapor deposition (CVD) growth of large-area (>2 cm2) patterned 2D vdW heterostructures composed of few layer, vertically-stacked MoS2 and WS2. Detailed structural characterizations by Raman spectroscopy and high-resolution/scanning transmission electron microscopy (HRTEM/STEM) directly evidence the structural integrity of two distinct 2D TMD layers with atomically sharp vdW heterointerfaces. Electrical transport measurements of these materials reveal diode-like behavior with clear current rectification, further confirming the formation of high-quality heterointerfaces. The intrinsic scalability and controllability of the CVD method presented in this study opens up a wide range of opportunities for emerging applications based on the unconventional functionalities of these uniquely structured materials.
Highlights
Two-dimensional (2D) van der Waal heterostructures composed of vertically-stacked multiple transition metal dichalcogenides (TMDs) such as molybdenum disulfide (MoS2) and tungsten disulfide (WS2) are envisioned to present unprecedented materials properties unobtainable from any other material systems
Vertically-stacked 2D MoS2/WS2 heterostructures were grown using a two-step process of metal deposition followed by sulfurization in a low-pressure chemical vapor deposition (CVD) (LPCVD) chamber
The deposited metal films were subsequently sulfurized in a LPCVD furnace at 600 °C under argon (Ar) environment, which converts Mo and W to MoS2 and WS2, respectively
Summary
Two-dimensional (2D) van der Waal (vdW) heterostructures composed of vertically-stacked multiple transition metal dichalcogenides (TMDs) such as molybdenum disulfide (MoS2) and tungsten disulfide (WS2) are envisioned to present unprecedented materials properties unobtainable from any other material systems Conventional fabrications of these hybrid materials have relied on the low-yield manual exfoliation and stacking of individual 2D TMD layers, which remain impractical for scaled-up applications. A few successful CVD growths of vertically-stacked WS2/MoS221,27,28, WSe2/MoS2 (or, MoS2/WSe2)[29], and WSe2/MoSe230 as well as vdW heteroepitaxy-based MoS2 heterostructures[31] have been demonstrated either via the co-reaction of metal-based precursors with chalcogens or via the sequential growth of one material on the other All these CVD-grown 2D TMD heterostructures are presently limited to be demonstrated on very small areas lacking a control of their location, size, thickness and uniformity. Detailed structural and electrical characterizations reveal that these hybrid materials well preserve their structural integrity and intrinsic electrical properties of individual constituting 2D TMDs
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