Journal
NANO LETTERS
Volume 15, Issue 9, Pages 6135-6141Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.5b02423
Keywords
2D heterostructures; two-step growth; MoSe2; WSe2; CVD
Categories
Funding
- Army Research Office MURI [W911NF-11-1-0362]
- FAME Center, one of six centers of STARnet, a Semiconductor Research Corporation
- MARCO
- DARPA
- U.S. Department of Energy, Office of Science, Basic Energy Science, Materials Sciences and Engineering Division
- U.S. Office of Naval Research MURI [N000014-09-1-1066]
- ORNL's Center for Nanophase Materials Sciences (CNMS), which is a DOE Office of Science User Facility
- Air Force Office of Scientific Research (AFOSR) [BAA-AFOSR-2013-0001]
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Two dimensional (2D) materials have attracted great attention due to their unique properties and atomic thickness. Although various 2D materials have been successfully synthesized with different optical and electrical properties, a strategy for fabricating 2D heterostructures must be developed in order to construct more complicated devices for practical applications. Here we demonstrate for the first time a two-step chemical vapor deposition (CVD) method for growing transition-metal dichalcogenide (TMD) heterostructures, where MoSe2 was synthesized first and followed by an epitaxial growth of WSe2 on the edge and on the top surface of MoSe2. Compared to previously reported one-step growth methods, this two-step growth has the capability of spatial and size control of each 2D component, leading to much larger (up to 169 mu m) heterostructure size, and cross-contamination can be effectively minimized. Furthermore, this two-step growth produces well-defined 2H and 3R stacking in the WSe2/MoSe2 bilayer regions and much sharper in-plane interfaces than the previously reported MoSe2/WSe2 heterojunctions obtained from one-step growth methods. The resultant heterostructures with WSe2/MoSe2 bilayer and the exposed MoSe2 monolayer display rectification characteristics of a p-n junction, as revealed by optoelectronic tests, and an internal quantum efficiency of 91% when functioning as a photodetector. A photovoltaic effect without any external gates was observed, showing incident photon to converted electron (IPCE) efficiencies of approximately 0.12%, providing application potential in electronics and energy harvesting.
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