Universität zu Köln

Wagner, Julian ORCID: 0000-0001-8325-9373, Kuhn, Henning, Bernhardt, Robin, Zhu, Jingyi ORCID: 0000-0003-0519-4724 and van Loosdrecht, Paul H. M. (2021). Trap induced long exciton intervalley scattering and population lifetime in monolayer WSe2. 2D Mater., 8 (3). BRISTOL: IOP PUBLISHING LTD. ISSN 2053-1583

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Abstract

Monolayer transition metal dichalcogenides (TMDCs) hold the best promise for next generation optoelectronic and valleytronic devices. However, their actual performance is usually largely affected by the presence of inevitable defects. Therefore, a detailed understanding of the influence of defects on the dynamic properties is crucial for optimizing near future implementations. Here, the exciton population and valley scattering dynamics in a chemical vapor deposition grown large size monolayer WSe2 with naturally abundant vacancy and boundary defects were systematically investigated using polarization controlled heterodyned transient grating spectroscopy at different excitation wavelengths and temperatures. Slow and multi-exponential decay dynamics of the exciton population were observed while no sign of any micron scale diffusive transport was identified, consistent with the effect of exciton trapping by defects. In general, two different kinds of exciton species were identified: one with short population lifetime (similar to 10 ps) and extremely fast intervalley scattering dynamics (<200 fs) and in contrast another one with a long population lifetime (>1 ns) and very slow intervalley scattering dynamics exceeding 100 ps. We assign the former to non-trapped excitons in the nanometer scale and the latter to defect-bound excitons. Temperature dependent intervalley scattering dynamics of the trapped excitons can be understood in terms of a two optical phonon dominated process at the K point in momentum space. Our findings highlight the importance of the intrinsic defects in monolayer TMDCs for manipulating exciton valley polarization and population lifetimes, which is key for future device applications.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Wagner, Julian UNSPECIFIED orcid.org/0000-0001-8325-9373 UNSPECIFIED Kuhn, Henning UNSPECIFIED UNSPECIFIED UNSPECIFIED Bernhardt, Robin UNSPECIFIED UNSPECIFIED UNSPECIFIED Zhu, Jingyi UNSPECIFIED orcid.org/0000-0003-0519-4724 UNSPECIFIED van Loosdrecht, Paul H. M. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-564886
DOI:	10.1088/2053-1583/abf625
Journal or Publication Title:	2D Mater.
Volume:	8
Number:	3
Date:	2021
Publisher:	IOP PUBLISHING LTD
Place of Publication:	BRISTOL
ISSN:	2053-1583
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language Materials Science, Multidisciplinary Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/56488