Nonlinear optical activities,especially second harmonic generation(SHG),are key phenomena in inversion-symmetrybroken two-dimensional(2D)transition metal dichalcogenides(TMDCs).On the other hand,anisotropic nonlinear ...Nonlinear optical activities,especially second harmonic generation(SHG),are key phenomena in inversion-symmetrybroken two-dimensional(2D)transition metal dichalcogenides(TMDCs).On the other hand,anisotropic nonlinear optical processes are important for unique applications in nano-nonlinear photonic devices with polarization functions,having become one of focused research topics in the field of nonlinear photonics.However,the strong nonlinearity and strong optical anisotropy do not exist simultaneously in common 2D materials.Here,we demonstrate strong secondorder and third-order susceptibilities of 64 pm/V and 6.2×10^(-19)m^(2)/V^(2),respectively,in the even-layer PdPSe,which has not been discovered in other common TMDCs(e.g.,MoS2).Strikingly,it also simultaneously exhibited strong SHG anisotropy with an anisotropic ratio of~45,which is the largest reported among all 2D materials to date,to the best of our knowledge.In addition,the SHG anisotropy ratio can be harnessed from 0.12 to 45(375 times)by varying the excitation wavelength due to the dispersion ofχ^(2)values.As an illustrative example,we further demonstrate polarized SHG imaging for potential applications in crystal orientation identification and polarization-dependent spatial encoding.These findings in 2D PdPSe are promising for nonlinear nanophotonic and optoelectronic applications.展开更多
Two-dimensional(2D)ferromagnets with out-of-plane(OOP)magnetic anisotropy are potential candidates for realizing the next-generation memory devices with ultra-low power consumption and high storage density.However,a s...Two-dimensional(2D)ferromagnets with out-of-plane(OOP)magnetic anisotropy are potential candidates for realizing the next-generation memory devices with ultra-low power consumption and high storage density.However,a scalable approach to synthesize 2D magnets with OOP anisotropy directly on the complimentary metal-oxide semiconductor(CMOS)compatible substrates has not yet been mainly explored,which hinders the practical application of 2D magnets.This work demonstrates a cascaded space confined chemical vapor deposition(CS-CVD)technique to synthesize 2D FexGeTe_(2) ferromagnets.The weight fraction of iron(Fe)in the precursor controls the phase purity of the as-grown FexGeTe2.As a result,high-quality Fe_(3)GeTe_(2) and Fe_(5)GeTe_(2) flakes have been grown selectively using the CS-CVD technique.Curie temperature(Tc)of the as-grown FexGeTe2 can be up to-280 K,nearly room temperature.The thickness and temperature-dependent magnetic studies on the Fe_(5)GeTe_(2) reveal a 2D Ising to 3D XY behavior.Also,Terahertz spectroscopy experiments on Fe_(5)GeTe_(2) display the highest conductivity among other FexGeTe_(2) 2D magnets.The results of this work indicate a scalable pathway for the direct growth and integration of 2D ternary magnets on CMOS-based substrates to develop spintronic memory devices.展开更多
基金supported by the Singapore Ministry of Education(MOET2EP50120-0009)Agency for Science,Technology and Research(A*STAR)(M22K2c0080,R23I0IR041,and A2090b0144)+3 种基金National Medical Research Council(NMRC)(Award number MOH-000927)National Research Foundation Singapore(Award No.NRF-CRP22-2019-0007 and NRF-CRP23-2019-0007)National Research Foundation,Singapore under its AI Singapore Programme(AISG Award No:AISG2-GC-2023-009)National Research Foundation(Award No.NRF2020-NRF-ISF004-3520).
文摘Nonlinear optical activities,especially second harmonic generation(SHG),are key phenomena in inversion-symmetrybroken two-dimensional(2D)transition metal dichalcogenides(TMDCs).On the other hand,anisotropic nonlinear optical processes are important for unique applications in nano-nonlinear photonic devices with polarization functions,having become one of focused research topics in the field of nonlinear photonics.However,the strong nonlinearity and strong optical anisotropy do not exist simultaneously in common 2D materials.Here,we demonstrate strong secondorder and third-order susceptibilities of 64 pm/V and 6.2×10^(-19)m^(2)/V^(2),respectively,in the even-layer PdPSe,which has not been discovered in other common TMDCs(e.g.,MoS2).Strikingly,it also simultaneously exhibited strong SHG anisotropy with an anisotropic ratio of~45,which is the largest reported among all 2D materials to date,to the best of our knowledge.In addition,the SHG anisotropy ratio can be harnessed from 0.12 to 45(375 times)by varying the excitation wavelength due to the dispersion ofχ^(2)values.As an illustrative example,we further demonstrate polarized SHG imaging for potential applications in crystal orientation identification and polarization-dependent spatial encoding.These findings in 2D PdPSe are promising for nonlinear nanophotonic and optoelectronic applications.
基金supported from National Research Foundation Singapore programme NRF-CRP22-2019-0007,NRF-CRP22-2019-0004 and NRF-CRP21-2018-0007supported by the Ministry of Education,Singapore,under its AcRF Tier 3 Programme‘Geometrical Quantum Materials’(MOE2018-T3-1-002),AcRF Tier 2(MOE2019-T2-2-105)and AcRF Tier 1 RG4/17 and RG7/18We also thank the funding support from National Research foundation(NRF-CRP22-2019-0004).
文摘Two-dimensional(2D)ferromagnets with out-of-plane(OOP)magnetic anisotropy are potential candidates for realizing the next-generation memory devices with ultra-low power consumption and high storage density.However,a scalable approach to synthesize 2D magnets with OOP anisotropy directly on the complimentary metal-oxide semiconductor(CMOS)compatible substrates has not yet been mainly explored,which hinders the practical application of 2D magnets.This work demonstrates a cascaded space confined chemical vapor deposition(CS-CVD)technique to synthesize 2D FexGeTe_(2) ferromagnets.The weight fraction of iron(Fe)in the precursor controls the phase purity of the as-grown FexGeTe2.As a result,high-quality Fe_(3)GeTe_(2) and Fe_(5)GeTe_(2) flakes have been grown selectively using the CS-CVD technique.Curie temperature(Tc)of the as-grown FexGeTe2 can be up to-280 K,nearly room temperature.The thickness and temperature-dependent magnetic studies on the Fe_(5)GeTe_(2) reveal a 2D Ising to 3D XY behavior.Also,Terahertz spectroscopy experiments on Fe_(5)GeTe_(2) display the highest conductivity among other FexGeTe_(2) 2D magnets.The results of this work indicate a scalable pathway for the direct growth and integration of 2D ternary magnets on CMOS-based substrates to develop spintronic memory devices.
