Strong modulation of optical properties in rippled 2D GaSe via strain engineering

Abstract

This is the Accepted Manuscript version of an article accepted for publication in Nanotechnology. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.1088/1361-6528/ab0bc1 ; Few-layer GaSe is one of the latest additions to the family of two-dimensional semiconducting crystals whose properties under strain are still relatively unexplored. Here, we study rippled nanosheets that exhibit a periodic compressive and tensile strain of up to 5%. The strain profile modifies the local optoelectronic properties of the alternating compressive and tensile regions, which translates into a remarkable shift of the optical absorption band-edge of up to 1.2 eV between crests and valleys. Our experimental observations are supported by theoretical results from density functional theory calculations performed for monolayers and multilayers (up to seven layers) under tensile and compressive strain. This large band gap tunability can be explained through a combined analysis of the elastic response of Ga atoms to strain and the symmetry of the wave functions ; Research supported by the Spanish MINECO through Grants MAT2017–88693-R, MAT2014-57915-R, FIS2016-80434- P (AEI/FEDER, EU), BES-2015-071316, the Ramón y Cajal programme RYC-2011-09345, the Fundación Ramón Areces and the María de Maeztu Programme for Units of Excellence in R&D (MDM-2014-0377), as well as from the Comunidad Autónoma de Madrid (CAM) MAD2D-CM Program (S2013/MIT-3007) and the European Union Seventh Framework Programme under grant agreement No. 604391 Graphene Flagship. JJP acknowledges Fulbright Fellowship for Sabbatical leave at University of Texas at Austin, EEUU. We acknowledge the computer resources and assistance provided by the Centro de Computación Científica of the Universidad Autónoma de Madrid