Strong Wavelength-Dependent Polarization-Resolved Second Harmonic Generation (SHG) in Large Few-Layer Ferroelectric SnSe Flakes

Li-Tien Huang^1*, Redhwan Moqbel¹, Chi Chen², Ming-Hao Lee³, Chi-Cheng Lee⁴, Kung-Hsuan Lin¹

¹Institute of Physics, Academia Sinica, Taipei, Taiwan
²Research Center for Applied Science, Academia Sinica, Taipei, Taiwan
³Center for Condensed Matter Sciences, National Taiwan University, Taipei, Taiwan
⁴Department of Physics, Tamkang University, New Taipei, Taiwan

* Presenter:Li-Tien Huang, email:lthuang@gate.sinica.edu.tw

2D multiferroic tin selenide (SnSe), a member of the group IV−VI monochalcogenides, has recently attracted significant interest for applications in optoelectronic, photovoltaic, and thermoelectric devices due to its unique physical properties. In this study, we synthesized ferroelectric SnSe few-layer flakes using the physical vapor deposition method on mica substrates, achieving a thickness of ~12 nm and lateral dimensions of 10 μm x 10 μm. Polarization-resolved second harmonic generation (SHG) microscopy was used to investigate the ferroelectric phases, crystal orientations, and orthogonal domains of the SnSe flakes. Notably, the SHG polarization patterns undergo significant changes between wavelengths of 800 nm and 1040 nm, with a peak SHG intensity observed at 1040 nm, demonstrating a susceptibility of approximately 1424 pm/V, which is three order of magnitude larger than that of a typical nonlinear crystal.

Keywords: Strong SHG, ferroelectric SnSe Few Layers, frequency dependent SHG