SnGa2GeS6: synthesis, structure, linear and nonlinear optical properties

Area of Science:

• Solid-state chemistry
• Materials science
• Crystallography

Background:

• Quaternary chalcogenides offer diverse properties.
• Exploration of new materials with nonlinear optical (NLO) properties is crucial for optical applications.
• The Sn/M/M'/Q (M = Ga, In; M' = Si, Ge; Q = S, Se, Te) system remains underexplored.

Purpose of the Study:

• Synthesize and characterize a new quaternary sulfide, SnGa2GeS6.
• Determine its crystal structure and bonding characteristics.
• Investigate its nonlinear optical and optical properties.

Main Methods:

• Single-crystal and powder X-ray diffraction for structure determination.
• Single-crystal growth.
• Powder second harmonic generation (SHG) measurements.
• UV-vis-NIR spectroscopy.
• First-principles electronic structure calculations.

Main Results:

• SnGa2GeS6 was successfully synthesized, representing the first member of the quaternary Sn/Ga/Ge/S system.
• It crystallizes in a new structure type within the non-centrosymmetric space group Fdd2.
• The structure features Sn(2+) in a distorted square-pyramidal coordination (SnS5) and Ga/Ge in tetrahedral coordination (MS4).
• A powder second harmonic generation signal was observed at 2 μm, approximately one-fourth the intensity of AgGaS2.
• Optical transitions were identified at 1.12 eV and 2.04 eV.

Conclusions:

• SnGa2GeS6 is a novel quaternary sulfide with a unique non-centrosymmetric crystal structure.
• The compound exhibits potential for nonlinear optical applications, evidenced by its SHG signal.
• The observed optical properties are consistent with its electronic structure and crystal packing.