Non‐Centrosymmetric 2D Nb₃SeI₇ with High In‐Plane Anisotropy and Optical Nonlinearity

Abstract

Integrating anisotropy and nonlinearity of physical properties in 2D materials is of great importance to the progress of nanoelectronic, nanophotonic, and nano‐optoelectronic applications. In this work, Nb3SeI7, a newly discovered ternary layered material with non‐centrosymmetric lattices, is introduced, which exhibits strong second harmonic generation (SHG), in‐plane anisotropic electricity, and light absorption. Symmetry breaking of 2D Nb3SeI7 induced by the polar off‐center displacement of niobium leads to a high nonlinear optical response with a second‐order susceptibility of 6.71 pm V−1 and a high anisotropic factor of photoresponsivity up to 4.6, which are higher than most of the 2D materials. These properties of 2D Nb3SeI7 create new possibilities for chip‐integrated nonlinear optics devices and future‐proof polarization‐sensitive optoelectronic systems.

Low-dimensional van der Waals materials for linear-polarization-sensitive photodetection: materials, polarizing strategies and applications

“…In contrast to the widely explored group VIB transition metal dichalcogenides, the fundamental atomic layers of a considerable portion of 2D vdWMs host in-plane anisotropy [105]. The typical members of this family include the group VA elemental semiconductors [106,107], IVA-VIA compounds [108,109], group VIII transition metal dichalcogenides [110,111], multielemental vdWMs [112][113][114], etc. Accordingly, the low-symmetry lattice structures endow these materials with anisotropic physical properties, such as the anisotropic energy dispersion, laying a solid foundation for the realization polarized devices.…”

Growth of Noncentrosymmetric Two-Dimensional Single Crystals

“…This method effectively lowers the metal precursor’s melting point by adsorbing and trapping evaporated molecules, ensuring a uniform distribution of the source (Figure a–c). More recently, Wang et al reported the synthesis of Nb 3 SeI 7 , a new ternary layered material via chemical vapor transport (CVT) . Nb 3 SeI 7 possesses a noncentrosymmetric lattice structure and exhibits pronounced SHG, in-plane anisotropic electrical properties, and optical absorption capabilities (Figure d–f).…”

“…219 Nb 3 SeI 7 possesses a noncentrosymmetric lattice structure and exhibits pronounced SHG, in-plane anisotropic electrical properties, and optical absorption capabilities (Figure23d−f).…”

Out-of-plane Emission Dipole of Second Harmonic Generation in Odd- and Even-layered vdWs Janus Nb3SeI7

“…Besides, Nb 3 SeI 7 can be easily exfoliated even down to the monolayer limit, making it a promising candidate for the integration of SHG with OP dipole emission. However, the experimental demonstration of OP dipole emission in Janus Nb 3 SeI 7 and its layer-dependence has not been achieved …”