TY - JOUR AU - Francisco-López, Adrián AU - Han, Bo AU - Lagarde, Delphine AU - Marie, Xavier AU - Urbaszek, Bernhard AU - Robert, Cedric AU - Goñi, Alejandro PY - 2019/06/21 Y2 - 2024/03/28 TI - On the impact of the stress situation on the optical properties of $WSe_2$ monolayers under high pressure JF - Papers in Physics JA - Pap. Phys. VL - 11 IS - SE - Articles DO - 10.4279/pip.110005 UR - https://www.papersinphysics.org/papersinphysics/article/view/484 SP - 110005 AB - <p>We have studied the optical properties of $WSe_2$ monolayers (ML) by means of photoluminescence (PL), PL excitation (PLE) and Raman scattering spectroscopy at room temperature and as a function of hydrostatic pressure up to ca. 12 GPa. For comparison the study comprises two cases: A single $WSe_2$ ML directly transferred onto one of the diamonds of the diamond anvil cell and a $WSe_2$ ML encapsulated into hexagonal boron nitride (hBN) layers. The pressure dependence of the A and B exciton, as determined by PL and PLE, respectively, is very different for the case of the bare $WSe_2$ ML and the $hBN/WSe_2-ML/hBN$ heterostructure. Whereas for the latter the A and B exciton energy increases linearly with increasing pressure at a rate of 3.5 to 3.8 meV/GPa, for the bare $WSe_2$ ML the A and B exciton energy decreases with a coefficient of -3.1 and -1.3 meV/GPa, respectively. We interpret that this behavior is due to a different stress situation. For a single ML the stress tensor is essentially uniaxial with the compressive stress component in the direction perpendicular to the plane of the ML. In contrast, for the substantially thicker $hBN/WSe_2-ML/hBN$ heterostructure the compression is hydrostatic. The results from an analysis of the pressure dependence of the frequency of Raman active modes comply with the interpretation of having a different stress situation in each case.</p><p><strong>Reviewed by:</strong> A. San Miguel, Institut Lumière Matière, Université de Lyon, France; <strong>Edited by:</strong> J. S. Reparaz</p> ER -