Synthesis of CaSnN2 via a High-Pressure Metathesis Reaction and the Properties of II-Sn-N2 (II = Ca, Mg, Zn) Semiconductors

Abstract

A novel ternary nitride semiconductor, CaSnN₂, with a layered rock-salt-type structure (R3̅m) was synthesized via a high-pressure metathesis reaction. The properties and structures of II-Sn-N₂ (II = Ca, Mg, Zn) semiconductors were also systematically studied, and the differences among them were revealed by comparison. These semiconductor materials showed a rock-salt- or wurtzite-type structure depending on the combined effect of the synthetic conditions and the characteristics of the group II elements. Additionally, the rock-salt-type structures of CaSnN₂ and MgSnN₂ (i.e., the ambient-pressure phase) were different from those predicted using first-principles calculations. Further, on the basis of first-principles calculations and consideration of the pressure effect, the recovered CaSnN₂ sample showed an R3̅m structure. CaSnN₂ and MgSnN₂ showed a band gap of 2.3–2.4 eV, which is suitable for overcoming the green-light-gap problem. These semiconductors also showed a strong cathode luminescence peak at room temperature, and generalized gradient approximation (GGA) calculations revealed that CaSnN₂ has a direct band gap. These inexpensive and nontoxic semiconductors (II-Sn-N₂ semiconductors (II = Ca, Mg, Zn)), with mid band gaps are required as pigments to replace cadmium-based materials. They can also be used in emitting devices and as photovoltaic absorbers, replacing In_xGa_1–xN semiconductors.