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This content will become publicly available on March 20, 2019

Title: Giant Mechano-Optoelectronic Effect in an Atomically Thin Semiconductor

Transition metal dichalcogenides (TMDs) are particularly sensitive to mechanical strain as they are capable of experiencing high atomic displacements without nucleating defects to release excess energy. Promising for photonic applications, it has been shown that as TMDs are scaled to a thickness of one monolayer, the photoluminescence response is dramatically enhanced due to the emergence of a direct electronic band gap, compared with multi-layer or bulk TMDs which typically exhibit indirect band gaps. Recently, mechanical strain has also been predicted to enable direct excitonic recombination in these materials, where large changes in the photoluminescence response will occur during an indirect-to-direct band gap transition brought on by elastic tensile strain. Here, we demonstrate a two orders of magnitude enhancement in the photoluminescence emission intensity in uniaxially strained single crystalline WSe 2 bilayers. Through a theoretical model which includes experimentally relevant system conditions, we determine this amplification to arise from a significant increase in direct excitonic recombination. Adding confidence to the high levels of elastic strain achieved in this report, we observe strain-independent mode-dependent Grüneisen parameters over the entire range of tensile strain (1– 3.59 %) which were obtained as 1.149±0.027, 0.307±0.061, and 0.357±0.103 for the E 2g, A 1g, and Amore » 2 1g optical phonon modes, respectively. Lastly, these results can inform the predictive strain-engineered design of other atomically thin indirect semiconductors, where a decrease in out-of-plane bonding strength will lead to an increase in the strength of strain-coupled optoelectronic effects.« less
 [1] ;  [2] ;  [3] ;  [4] ;  [4] ;  [5] ;  [6] ;  [2] ; ORCiD logo [1]
  1. Univ. of Connecticut, Storrs, CT (United States). Dept. of Mechanical Engineering; Univ. of Connecticut, Storrs, CT (United States). Inst. of Materials Science
  2. Univ. of Connecticut, Storrs, CT (United States). Inst. of Materials Science; Univ. of Connecticut, Storrs, CT (United States). Dept. of Materials Science and Engineering
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Molecular Foundry
  4. Univ. of Connecticut, Storrs, CT (United States). Dept. of Mechanical Engineering
  5. US Army Research Lab., Adelphi, MD (United States); General Technical Services, LLC, Wall, NJ (United States)
  6. US Army Research Lab., Adelphi, MD (United States)
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Nano Letters
Additional Journal Information:
Journal Volume: 18; Journal Issue: 4; Journal ID: ISSN 1530-6984
American Chemical Society
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of Connecticut, Storrs, CT (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
36 MATERIALS SCIENCE; band gap engineering; optoelectronics; photoluminescence; Strain engineering; transition metal dichalcogenide; tungsten diselenide; 77 NANOSCIENCE AND NANOTECHNOLOGY; strain engineering
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1430687