Direct observation of the transition from indirect to direct bandgap in atomically thin epitaxial MoSe2

Yi Zhang; Tay Rong Chang; Bo Zhou; Yong Tao Cui; Hao Yan; Zhongkai Liu; Felix Schmitt; James Lee; Rob Moore; Yulin Chen; Hsin Lin; Horng Tay Jeng; Sung Kwan Mo; Zahid Hussain; Arun Bansil; Zhi Xun Shen

doi:10.1038/nnano.2013.277

Direct observation of the transition from indirect to direct bandgap in atomically thin epitaxial MoSe₂

Yi Zhang, Tay Rong Chang, Bo Zhou, Yong Tao Cui, Hao Yan, Zhongkai Liu, Felix Schmitt, James Lee, Rob Moore, Yulin Chen, Hsin Lin, Horng Tay Jeng, Sung Kwan Mo, Zahid Hussain, Arun Bansil, Zhi Xun Shen

Research output: Contribution to journal › Article › peer-review

1161 Scopus citations

Abstract

Quantum systems in confined geometries are host to novel physical phenomena. Examples include quantum Hall systems in semiconductors and Dirac electrons in graphene. Interest in such systems has also been intensified by the recent discovery of a large enhancement in photoluminescence quantum efficiency and a potential route to valleytronics in atomically thin layers of transition metal dichalcogenides, MX₂ (M = Mo, W; X = S, Se, Te), which are closely related to the indirect-to-direct bandgap transition in monolayers. Here, we report the first direct observation of the transition from indirect to direct bandgap in monolayer samples by using angle-resolved photoemission spectroscopy on high-quality thin films of MoSe₂ with variable thickness, grown by molecular beam epitaxy. The band structure measured experimentally indicates a stronger tendency of monolayer MoSe₂ towards a direct bandgap, as well as a larger gap size, than theoretically predicted. Moreover, our finding of a significant spin-splitting of ∼180 meV at the valence band maximum of a monolayer MoSe₂ film could expand its possible application to spintronic devices.

Original language	English
Pages (from-to)	111-115
Number of pages	5
Journal	Nature Nanotechnology
Volume	9
Issue number	2
DOIs	https://doi.org/10.1038/nnano.2013.277
State	Published - Feb 2014
Externally published	Yes

Funding

The work at the ALS is supported by the US Department of Energy (DoE) Office of Basic Energy Science contract no. DE-AC02-05CH11231. The work at the Stanford Institute for Materials and Energy Sciences and Stanford University is supported by the US DoE Office of Basic Energy Science under contract no. DE-AC02-76SF00515. The work at Oxford University is supported from a Defense Advanced Research Projects Agency MesoDynamic Architectures (DARPA MESO) project (no. 187 N66001-11-1-4105). The work at Northeastern University is supported by the US DoE Office of Basic Energy Sciences under contract no. DE-FG02-07ER46352 and benefited from Northeastern University’s Advanced Scientific Computation Center (ASCC), theory support at the Advanced Light Source, Berkeley, and the allocation of time at the National Energy Research Scientific Computing Center (NERSC) supercomputing centre through DoE grant no. DE-AC02-05CH11231. T.R.C. and H.T.J. are supported by the National Science Council, Taiwan. H.T.J. also thanks National Center for High-Performance Computing (NCHC), Computer and Information Network Center (CINC) – National Taiwan University (NTU) and National Center for Theoretical Sciences (NCTS), Taiwan, for technical support.

Funders	Funder number
Defense Advanced Research Projects Agency MesoDynamic Architectures	187 N66001-11-1-4105
Stanford Institute for Materials and Energy Sciences
US DOE Office of Basic Energy Sciences	DE-FG02-07ER46352
U.S. Department of Energy
Stanford University	DE-AC02-76SF00515
Basic Energy Sciences	DE-AC02-05CH11231
Northeastern University
National Science Council

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title = "Direct observation of the transition from indirect to direct bandgap in atomically thin epitaxial MoSe2",

abstract = "Quantum systems in confined geometries are host to novel physical phenomena. Examples include quantum Hall systems in semiconductors and Dirac electrons in graphene. Interest in such systems has also been intensified by the recent discovery of a large enhancement in photoluminescence quantum efficiency and a potential route to valleytronics in atomically thin layers of transition metal dichalcogenides, MX2 (M = Mo, W; X = S, Se, Te), which are closely related to the indirect-to-direct bandgap transition in monolayers. Here, we report the first direct observation of the transition from indirect to direct bandgap in monolayer samples by using angle-resolved photoemission spectroscopy on high-quality thin films of MoSe2 with variable thickness, grown by molecular beam epitaxy. The band structure measured experimentally indicates a stronger tendency of monolayer MoSe2 towards a direct bandgap, as well as a larger gap size, than theoretically predicted. Moreover, our finding of a significant spin-splitting of ∼180 meV at the valence band maximum of a monolayer MoSe2 film could expand its possible application to spintronic devices.",

author = "Yi Zhang and Chang, {Tay Rong} and Bo Zhou and Cui, {Yong Tao} and Hao Yan and Zhongkai Liu and Felix Schmitt and James Lee and Rob Moore and Yulin Chen and Hsin Lin and Jeng, {Horng Tay} and Mo, {Sung Kwan} and Zahid Hussain and Arun Bansil and Shen, {Zhi Xun}",

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Direct observation of the transition from indirect to direct bandgap in atomically thin epitaxial MoSe₂

Abstract

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