The angle dependence of optical phonon modes of an AlN bulk single crystal from the m-plane（1100） and c-plane（0001） surfaces, respectively, is investigated by polarized Raman spectroscopy in a backscattering confi...The angle dependence of optical phonon modes of an AlN bulk single crystal from the m-plane（1100） and c-plane（0001） surfaces, respectively, is investigated by polarized Raman spectroscopy in a backscattering configuration at room temperature. Corresponding Raman selection rules are derived according to measured scattering geometries to illustrate the angle dependence. The angle-dependent intensities of phonon modes are discussed and compared to theoretical scattering intensities, yielding the Raman tensor elements of A1（TO）, E22, E1（TO）, and A1（LO） phonon modes and the relative phase difference between the two complex elements of A1（TO）. Furthermore, the Raman tensor of wurtzite AlN is compared with that of wurtzite ZnO reported in previous work, revealing the intrinsic differences of lattice vibration dynamics between AlN and ZnO.展开更多
Silicon carbide(SiC),a group IV compound and wide-bandgap semiconductor for high-power,high-frequency and high-temperature devices,demonstrates excellent inherent properties for power devices and specialized high-end ...Silicon carbide(SiC),a group IV compound and wide-bandgap semiconductor for high-power,high-frequency and high-temperature devices,demonstrates excellent inherent properties for power devices and specialized high-end markets.Solution growth is thermodynamically favorable for producing SiC single crystal ingots with ultra-low dislocation density as the crystallization is driven by the supersaturation of carbon dissolved in Si-metal solvents.Meanwhile,solution growth is conducive to the growth of both N-and P-type SiC,with doping concentrations ranging from 10^(14)to 10^(19)cm^(-3).To date,4-inch 4H-SiC substrates with a thickness of 15 mm produced by solution growth have been unveiled,while substrates of 6 inches and above are still under development.Based on top-seeded solution growth(TSSG),several growth techniques have been developed including solution growth on a concave surface(SGCS),melt-back,accelerated crucible rotation technique(ACRT),two-step growth,and facet growth.Multi-parameters of the solution growth including meniscus,solvent design,flow control,dislocation conversion,facet growth,and structures of graphite components make high-quality single crystal growth possible.In this paper,the solution growth techniques and corresponding parameters involved in SiC bulk growth were reviewed.展开更多
Perovskite is a magic material with a structure similar to calcium titanate(CaTi03).Among perovskite materials,halide perovskite has gained considerable attention owing to its superior semiconducting properties such a...Perovskite is a magic material with a structure similar to calcium titanate(CaTi03).Among perovskite materials,halide perovskite has gained considerable attention owing to its superior semiconducting properties such as direct band gap and relatively small effective mass of electrons and holes.In recent years,the power conversion efficiency of halide perovskite solar cells has been continuously refreshed.The growth of bulk halide perovskite single crystals(PSCs)has become crucial to the investigation of their intrinsic properties.In the entire preparation process,the growth method generally plays a significant role,which determines the quality and size of the target PSCs.In this review,we summarized the existing mainstream synthetic methods for growing bulk PSCs including solution and solid-phase methods.We discussed the characteristics of these methods and the influence of the growth parameters on the quality and size of the resulting PSCs.Moreover,we briefly introduce the applications of PSCs as semiconductors in photodetectors and gas sensors.Understanding the growth behaviors of PSCs is insightful for future research on their synthesis and applications.展开更多
A organic nonlinear optical material, L-alanine maleate (LALM) was synthesized. Bulk Single crystals of LALM have been grown by slow cooling method with a solution pH of 5. The solubility of L-alanine maleate has been...A organic nonlinear optical material, L-alanine maleate (LALM) was synthesized. Bulk Single crystals of LALM have been grown by slow cooling method with a solution pH of 5. The solubility of L-alanine maleate has been deter-mined for various temperatures. Large size sin-gle crystal of 2.0 x 1.2 x 0.8 cm3 has been grown with reasonable growth rate along the three crystallographic directions by optimizing the growth parameters. The structure of LALM crys- tal was studied by single-crystal X-ray diffrac-tion analysis. The presence of functional groups was confirmed by Fourier transform infrared spectroscopy. The LALM crystal was analysed for its thermal and mechanical behaviours. The grown crystals have also been subjected to linear and non-linear optical property studies. From these studies, it is inferred that the LALM crystals exhibit better thermal and mechanical stabilities with improved optical properties. Thus satisfies the essential requirements for optical device fabrication.展开更多
基金financially supported by the Special Program for the State Key Program of National Natural Science of China (No. 61136001)the Major Research Plan of the National Natural Science Foundation of China (No. 91333207)
文摘The angle dependence of optical phonon modes of an AlN bulk single crystal from the m-plane（1100） and c-plane（0001） surfaces, respectively, is investigated by polarized Raman spectroscopy in a backscattering configuration at room temperature. Corresponding Raman selection rules are derived according to measured scattering geometries to illustrate the angle dependence. The angle-dependent intensities of phonon modes are discussed and compared to theoretical scattering intensities, yielding the Raman tensor elements of A1（TO）, E22, E1（TO）, and A1（LO） phonon modes and the relative phase difference between the two complex elements of A1（TO）. Furthermore, the Raman tensor of wurtzite AlN is compared with that of wurtzite ZnO reported in previous work, revealing the intrinsic differences of lattice vibration dynamics between AlN and ZnO.
文摘Silicon carbide(SiC),a group IV compound and wide-bandgap semiconductor for high-power,high-frequency and high-temperature devices,demonstrates excellent inherent properties for power devices and specialized high-end markets.Solution growth is thermodynamically favorable for producing SiC single crystal ingots with ultra-low dislocation density as the crystallization is driven by the supersaturation of carbon dissolved in Si-metal solvents.Meanwhile,solution growth is conducive to the growth of both N-and P-type SiC,with doping concentrations ranging from 10^(14)to 10^(19)cm^(-3).To date,4-inch 4H-SiC substrates with a thickness of 15 mm produced by solution growth have been unveiled,while substrates of 6 inches and above are still under development.Based on top-seeded solution growth(TSSG),several growth techniques have been developed including solution growth on a concave surface(SGCS),melt-back,accelerated crucible rotation technique(ACRT),two-step growth,and facet growth.Multi-parameters of the solution growth including meniscus,solvent design,flow control,dislocation conversion,facet growth,and structures of graphite components make high-quality single crystal growth possible.In this paper,the solution growth techniques and corresponding parameters involved in SiC bulk growth were reviewed.
基金the National Natural Science Foundation of China(Grant No.61875119)the Program for Professor of Special Appointment(Eastern Scholar)at Shanghai Institutions of Higher Learning,Shanghai Rising-Star Program(Grant No.19QA1404000)Shanghai Talent Development Fund,and the "Chen Guang" project supported by Shanghai Municipal Education Commission and Shanghai Education Development Foundation(Grant No.18CG63).
文摘Perovskite is a magic material with a structure similar to calcium titanate(CaTi03).Among perovskite materials,halide perovskite has gained considerable attention owing to its superior semiconducting properties such as direct band gap and relatively small effective mass of electrons and holes.In recent years,the power conversion efficiency of halide perovskite solar cells has been continuously refreshed.The growth of bulk halide perovskite single crystals(PSCs)has become crucial to the investigation of their intrinsic properties.In the entire preparation process,the growth method generally plays a significant role,which determines the quality and size of the target PSCs.In this review,we summarized the existing mainstream synthetic methods for growing bulk PSCs including solution and solid-phase methods.We discussed the characteristics of these methods and the influence of the growth parameters on the quality and size of the resulting PSCs.Moreover,we briefly introduce the applications of PSCs as semiconductors in photodetectors and gas sensors.Understanding the growth behaviors of PSCs is insightful for future research on their synthesis and applications.
文摘A organic nonlinear optical material, L-alanine maleate (LALM) was synthesized. Bulk Single crystals of LALM have been grown by slow cooling method with a solution pH of 5. The solubility of L-alanine maleate has been deter-mined for various temperatures. Large size sin-gle crystal of 2.0 x 1.2 x 0.8 cm3 has been grown with reasonable growth rate along the three crystallographic directions by optimizing the growth parameters. The structure of LALM crys- tal was studied by single-crystal X-ray diffrac-tion analysis. The presence of functional groups was confirmed by Fourier transform infrared spectroscopy. The LALM crystal was analysed for its thermal and mechanical behaviours. The grown crystals have also been subjected to linear and non-linear optical property studies. From these studies, it is inferred that the LALM crystals exhibit better thermal and mechanical stabilities with improved optical properties. Thus satisfies the essential requirements for optical device fabrication.
