Title: Ultrasensitive tunability of the direct bandgap of 2D [Twp-dimensional] InSe flakes via strain engineering

Abstract

InSe, a member of the layered materials family, is a superior electronic and optical material which retains a direct bandgap feature from the bulk to atomically thin few-layers and high electronic mobility down to a single layer limit. We, for the first time, exploit strain to drastically modify the bandgap of two-dimensional (2D) InSe nanoflakes. We demonstrated that we could decrease the bandgap of a few-layer InSe flake by 160 meV through applying an in-plane uniaxial tensile strain to 1.06% and increase the bandgap by 79 meV through applying an in-plane uniaxial compressive strain to 0.62%, as evidenced by photoluminescence (PL) spectroscopy. The large reversible bandgap change of ~239 meV arises from a large bandgap change rate (bandgap strain coefficient) of few-layer InSe in response to strain, ~154 meV/% for uniaxial tensile strain and ~140 meV/% for uniaxial compressive strain, representing the most pronounced uniaxial strain-induced bandgap strain coefficient experimentally reported in 2D materials. We developed a theoretical understanding of the strain-induced bandgap change through first-principles DFT and GW calculations. We also confirmed the bandgap change by photoconductivity measurements using excitation light with different photon energies. In conclusion, the highly tunable bandgap of InSe in the infrared regime should enablemore » a wide range of applications, including electro-mechanical, piezoelectric and optoelectronic devices.« less

Authors:

Li, Yang ^[1]; Wang, Tianmeng ^[1]; Wu, Meng ^[2]; Cao, Ting ^[2]; Chen, Yanwen ^[1]; Sankar, Raman  ^[3];

• Search DOE PAGES for author "Sankar, Raman"
• Search DOE PAGES for ORCID "0000-0003-4702-2517"

Ulaganathan, Rajesh K. ^[3]; Chou, Fangcheng ^[3]; Wetzel, Christian ^[4]; Xu, Cheng-Yan  ^[5];

• Search DOE PAGES for author "Xu, Cheng-Yan"
• Search DOE PAGES for ORCID "0000-0002-7835-6635"

Louie, Steven G. ^[2]; Shi, Su-Fei  ^[6]

• Search DOE PAGES for author "Shi, Su-Fei"
• Search DOE PAGES for ORCID "0000-0001-5158-805X"

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+ Show Author Affiliations

1. Rensselaer Polytechnic Inst., Troy, NY (United States). Dept. of Chemical and Biological Engineering
2. Univ. of California, Berkeley, CA (United States). Dept. of Physics; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Sciences Division
3. Academia Sinica, Taipei (Taiwan). Inst. of Physics; National Taiwan Univ., Taipei (Taiwan). Center for Condensed Matter Science
4. Rensselaer Polytechnic Inst., Troy, NY (United States). Dept. of Physics and Astronomy
5. Harbin Inst. of Technology (China). School of Materials Science and Engineering
6. Rensselaer Polytechnic Inst., Troy, NY (United States). Dept. of Chemical and Biological Engineering; Rensselaer Polytechnic Inst., Troy, NY (United States). Dept. of Electrical, Computer and System Engineering

Publication Date:

Mon Jan 29 00:00:00 EST 2018

Research Org.:

Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC)

OSTI Identifier:

1461129

Grant/Contract Number:  

AC02-05CH11231

Resource Type:

Accepted Manuscript

Journal Name:

2D Materials

Additional Journal Information:

Journal Volume: 5; Journal Issue: 2; Journal ID: ISSN 2053-1583

Publisher:

IOP Publishing

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; 2D materials; flexible optoelectronics; strain; band structure engineering; InSe