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BaHgGeSe4 and SrHgGeSe4: Two New Hg-based Infrared Nonlinear Optical Materials
摘要： New practically usable IR nonlinear optical (NLO) crystals, especially those suitable for high-efficient pumping of the commercial 1 μm laser, are in urgent demand. However, only a few new IR NLO materials have been grown into bulk crystals and realized IR laser output during the past twenty years due to the extreme difficulty in achieving the coexistence of various strongly-correlated properties. In the manuscript, based on the bonding characteristics of the Hg element and an efficient screening strategy for high-performance new crystals, we identified two new Hg-based IR nonlinear (NLO) materials, BaHgGeSe4 and SrHgGeSe4. They crystallize in the polar space group Ama2 with the distorted HgSe4 and GeSe4 tetrahedra aligned parallelly. They exhibit exceptional balance among all the preferred properties for practical applications, especially for high-efficient pumping of the commercial 1 μm laser: Their large band gap (~2.5 eV) can avoid the two-photon absorption of 1 μm laser and increase the laser damage threshold; They are phase matchable with very strong NLO response (5×AgGaS2); They can cover both the 3-5 μm and 8-12 μm atmospheric windows. Moreover, they melt congruently, which indicate that bulk crystals can be obtained by the Bridgman method. Their overall properties outperform the traditional materials AgGaQ2 (Q = S, Se) in a large degree. Detailed structural analysis and calculations elucidate the crucial role of cations in regulating the packing of the anionic groups and that of the highly-polarizable HgSe4 in balancing optical properties.
关键词： phase matchability,second harmonic generation,BaHgGeSe4,IR nonlinear optical materials,SrHgGeSe4,congruent-melting,Hg-based chalcogenides
更新于2025-11-19 16:56:35
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Structural and thermoelectric properties of Se doped In <sub/>2</sub> Te <sub/>3</sub> thin films
摘要： The Se-Te based chalcogenides exhibit novel property of Phase Change Memory (PCM) which has potential applications in electrical non-volatile memories. These materials are also suitable in thermal to electrical energy conversions and, hence, of potential interest in energy sustainability as thermoelectric devices. In this study, the Se doped In2Te3 thin films were prepared by thermal evaporation and were annealed at 250 ?C and 300 ?C in Argon gas. The X-ray diffraction spectra show that thermal annealing leads to the phase transitions in Se doped In2Te3 into binary phases of In2Se3 and In2Te3. The surface morphology of the films exhibits the grains of spherical nature. Annealing also decreases the energy band gap due to the presence of two phases. From the four probe and photoconductivity measurements, a large contrast in electrical resistance between the amorphous and crystalline states is found with a variation of a few orders of magnitude. The electrical transport properties such as the electrical resistivity, Seebeck coefficient and the power factor were measured in the temperature range from 300 K to 430 K. All the deposited and annealed thin films exhibit n-type conductivity with the Seebeck coefficient ranging from -338 μVK-1 to -510 μVK-1. An increase in thermoelectric power of 25% is observed in the 300 ?C annealed films in comparison to the as-deposited films. Moreover, the lower Se doped In2(Te0.96Se0.04)3 compound exhibits a better thermoelectric performance compared to the In2(Te0.90Se0.1)3 composition. This study shows the multifunctional nature of Se doped In2Te3 both for PCM and thermoelectric applications.
关键词： power factor,Seebeck coefficient,Phase Change Memory,X-ray diffraction,thermal evaporation,Se-Te based chalcogenides,electrical resistance,thermoelectric devices
更新于2025-09-10 09:29:36