Second harmonic generation of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>Mo</mml:mi><mml:msub><mml:mi>Si</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">N</mml:mi><mml:mn>4</mml:mn></mml:msub></mml:mrow></mml:math>-type layers
Lei Kang, Zheshuai Lin
Abstract
The recently discovered two-dimensional (2D) layered semiconductor $\mathrm{Mo}{\mathrm{Si}}_{2}{\mathrm{N}}_{4}$ has aroused great interest due to its unique 2D material characteristics. In this study, we found that differences in the structural details for $\mathrm{Mo}{\mathrm{Si}}_{2}{\mathrm{N}}_{4}$ may lead to differences in the intensity of second harmonic generation (SHG) and its response to strain. Accordingly, SHG can be used as a simple technique to identify the structural details of this system. We further calculated the SHG effects of $\mathrm{Mo}{\mathrm{Si}}_{2}{\mathrm{N}}_{4}$ derivatives and investigated their strain-regulation mechanism, especially including the anomalous SHG responses under strain for $\mathrm{Mo}{\mathrm{Si}}_{2}{\mathrm{P}}_{4}$ and $\mathrm{Mo}{\mathrm{Ge}}_{2}{\mathrm{P}}_{4}$, differing from other known 2D materials. The studies may have forward-looking significance for the research of nonlinear optics and optoelectronics in this novel 2D material system.