Uniaxial strain tuning of Raman spectra of a <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow><mml:mi>ReS</mml:mi></mml:mrow><mml:mn>2</mml:mn></mml:msub></mml:math> monolayer
Iris Niehues, Thorsten Deilmann, Joanna Kutrowska-Girzycka, Alireza Taghizadeh, L. Bryja, Ursula Wurstbauer, Rudolf Bratschitsch, J. Jadczak
Abstract
In contrast to the intensively investigated transition metal dichalcogenides like ${\mathrm{MoS}}_{2}$, ${\mathrm{ReS}}_{2}$ crystals possess a reduced in-plane symmetry, leading to anisotropic optical properties. Here, we report on the impact of strain on the Raman response of a ${\mathrm{ReS}}_{2}$ monolayer. Since mechanical strain can be used to shift the Raman-active phonon frequencies, we apply uniaxial tensile strain of up to 0.74% along the Re-chain direction ($x$ axis) of the atomically thin crystal and measure the Raman response with the scattered light polarized parallel and perpendicular to the strain direction along the $x$ axis. Complementarily, we carry out ab initio calculations to determine the phonon energies and Raman intensities under strain. We find a shift to lower energies for all phonon modes when tensile strain is applied to the monolayer. The determined gauge factors/Gr\"uneisen parameters are in good agreement between experiment and theory. Our study demonstrates that the optomechanical properties of ${\mathrm{ReS}}_{2}$ can be tuned by external straining, which is of importance for potential future strain-sensor applications, e.g., in the biomedical sector.