Substrate Interference and Strain in the Second-Harmonic Generation from MoSe<sub>2</sub> Monolayers
S. Puri, Sneha Patel, José Luis Cabellos, Luis Enrique Rosas-Hernandez, Katlin Reynolds, Hugh Churchill, Salvador Barraza‐Lopez, Bernardo S. Mendoza, H. Nakamura
Abstract
High Resolution Image Download MS PowerPoint Slide Nonlinear optical materials of atomic thickness, such as non-centrosymmetric 2H transition metal dichalcogenide monolayers, have a second-order nonlinear susceptibility (χ (2) ) whose intensity can be tuned by strain. However, whether χ (2) is enhanced or reduced by tensile strain is a subject of conflicting reports. Here, we grow high-quality MoSe 2 monolayers under controlled biaxial strain created by two different substrates and study their linear and nonlinear optical responses with a combination of experimental and theoretical approaches. Up to a 15-fold overall enhancement in second-harmonic generation (SHG) intensity is observed from MoSe 2 monolayers grown on SiO 2 when compared to its value on a Si 3 N 4 substrate. By considering an interference contribution from different dielectrics and their thicknesses, a factor of 2 enhancement of χ (2) was attributed to the biaxial strain: substrate interference and strain are independent handles to engineer the SHG strength of non-centrosymmetric 2D materials.