Li2HgMS4 (M = Si, Ge, Sn): New Quaternary Diamond-Like Semiconductors for Infrared Laser Frequency Conversion

A new family of quaternary diamond-like semiconductors (DLSs), Li2HgMS4 (M = Si, Ge, Sn), were successfully discovered for the first time. All of them are isostructural and crystallize in the polar space group (Pmn21). Seen from their structures, they exhibit a three-dimensional (3D) framework structure that is composed of countless 2D honeycomb layers stacked along the c axis. An interesting feature, specifically, that the LiS4 tetrahedra connect with each other to build a 2D layer in the ac plane, is also observed. Experimental investigations show that their nonlinear optical responses are about 0.8 for Li2HgSiS4, 3.0 for Li2HgGeS4, and 4.0 for Li2HgSnS4 times that of benchmark AgGaS2 at the 55–88 μm particle size, respectively. In addition, Li2HgSiS4 and Li2HgGeS4 also have great laser-damage thresholds that are about 3.0 and 2.3 times that of powdered AgGaS2, respectively. The above results indicate that title compounds can be expected as promising IR NLO candidates.