Heterovalent cations substitution to design asymmetric chalcogenides with promising nonlinear optical performances

Abstract

Metal chalcogenides are charming candidates for nonlinear optical (NLO) materials due to their multiple functional structural units and large polarizability. Here, isostructural Sn-based chalcogenides BaZnSnQ₄ (Q = S, Se) were successfully synthesized based on the idea of heterovalent cations co-substitution of the Ga site in the parent BaGa₂Se₄. They crystallize in an orthorhombic system with polar space group Fdd2. Their structures are built by the NLO functional motifs ZnQ₄ and SnQ₄ tetrahedra. BaZnSnS₄ (1) and BaZnSnSe₄ (2) exhibit good SHG effects (0.6 and 1.0 times than that of AgGaS₂) and also show type-I phase-matchable behaviors. In addition, their laser-induced damage thresholds are about 9.8 and 5.7 times higher than that of AgGaS₂, respectively. BaZnSnS₄ possesses a larger bandgap (3.25 eV) among the quaternary chalcogenide AM^IIM^IVQ₄ (A = Sr, Ba; M^II = Zn, Cd, Hg; M^IV = Si, Ge, Sn; Q = S, Se) system. On the basis of theoretical calculation result, the source of SHG responses can be assigned to the synergetic effect of large distorted tetrahedral units. The achievement of this work provides a route to obtain new infrared NLO materials.