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arXiv · 2407.01339

Substrate interference and strain in the second harmonic generation from MoSe$_2$ monolayers

S. Puri·S. Patel·J. L. Cabellos·L. E. Rosas-Hernandez·S. Barraza-Lopez·B. Mendoza·H. Nakamura
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Abstract

Nonlinear optical materials of atomic thickness--such as non-centrosymmetric 2H transition metal dichalcogenide monolayers--have a second order nonlinear susceptibility ($\chi^{(2)}$) whose intensity can be tuned by strain. However, whether $\chi^{(2)}$ 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 non-linear optical responses with a combination of experimental and theoretical approaches. A 15-fold overall enhancement in second harmonic generation (SHG) intensity is observed on MoSe$_2$ monolayers grown on SiO$_2$ when compared to its value when on a Si$_3$N$_4$ substrate. A seven-fold enhancement was ascertained to substrate interference, and a factor of two to the enhancement of $\chi^{(2)}$ arising from biaxial strain: substrate interference and strain are independent handles to engineer the SHG strength of non-centrosymmetric 2D materials.

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S. Puri, S. Patel, J. L. Cabellos, L. E. Rosas-Hernandez, S. Barraza-Lopez, B. Mendoza, H. Nakamura. 2024-07-01. Substrate interference and strain in the second harmonic generation from MoSe$_2$ monolayers. https://doi.org/10.1021/acs.nanolett.4c03880

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