Considering both the effects of the interfacial normal velocity dependence of solute segregation and the local nonequilibrium solute diffusion,an extended free dendritic growth model was analyzed.Compared with the pre...Considering both the effects of the interfacial normal velocity dependence of solute segregation and the local nonequilibrium solute diffusion,an extended free dendritic growth model was analyzed.Compared with the predictions from the dendritic model with isosolutal interface assumption,the transition from solutal dendrite to thermal dendrite moves to higher undercoolings,i.e.,the region of undercoolings with solute controlled growth is extended.At high undercoolings,the transition from the mainly thermal-controlled growth to the purely thermal-controlled growth is not sharp as predicted by the isosolute model,but occurs in a range of undercooling,due to both the effects of the interfacial normal velocity dependence of solute segregation and the local nonequilibrium solute diffusion.Model test indicates that the present model can give a satisfactory agreement with the available experimental data for the Ni-0.7% B（mole fraction） alloy.展开更多
The mixed P3HT （poly（3-hexylthiophene）） and [6,6]-PCBM （phenyl C61-butyric acid methyl ester） organic thin films were investigated for electronic structure using UV-Vis spectrophotometer and PESA （photo-electro...The mixed P3HT （poly（3-hexylthiophene）） and [6,6]-PCBM （phenyl C61-butyric acid methyl ester） organic thin films were investigated for electronic structure using UV-Vis spectrophotometer and PESA （photo-electron spectroscopy in air）. Furthermore, ESR （electron spin resonance） and AFM （atomic force microscopy） were used to investigate the surface morphology and molecular orientation, respectively. ESR analysis indicated the molecular orientation of the P3HT crystalline in the blend thin films, which the crystalline oriented normal to the substrate with distribution of 35°. AFM images indicated that the surface morphology of P3HT film was affected by the presence of PCBM nanoparticles. Solution-processed OTFTs （organic thin-film transistors） based on P3HT/PCBM blend thin film in a top source-drain contact structure was fabricated, and the electrical characteristics of the devices were also investigated. A unipolar property with p-channel characteristics were obtained in glove box measurement.展开更多
Metal-semiconductor field effect transistors (MESFETs) were fabricated on H-terminated polycrystalline diamond.The DC characteristics of the p-channel MESFET showed a maximum drain current density of 204 mA/mm at a ga...Metal-semiconductor field effect transistors (MESFETs) were fabricated on H-terminated polycrystalline diamond.The DC characteristics of the p-channel MESFET showed a maximum drain current density of 204 mA/mm at a gate-source voltage of 6 V,and a maximum transconductance of 20 mS/mm at a gate-source voltage of 1.5 V.The small signal S-parameters of MESFET with 2 100 m gate width and 2 m gate length were measured.An extrinsic cut-off frequency (fT) of 1.7 GHz and the maximum oscillation frequency (fmax) of 2.5 GHz were obtained,which was the first report on diamond MESFETs with RF characteristics in China.展开更多
Two-dimensional(2D)superconductors have intriguing physical properties and abundant potential applications.Recently,2D superconductingα-Mo2C and facecentered cubic Mo2C have been controllably prepared and they bring ...Two-dimensional(2D)superconductors have intriguing physical properties and abundant potential applications.Recently,2D superconductingα-Mo2C and facecentered cubic Mo2C have been controllably prepared and they bring new viewpoints to carbon-based superconductivity.Although molybdenum carbides(Mo-Cs)have multiple crystalline stacking orders,there are still few structures reported for the lack of higher energy supply during growth.In this study,we report a two-step vapor deposition method to grow superconducting η-Mo3C2 films with different thicknesses,with the assistance of controllable plasma power.The grownη-Mo3C2 films show polycrystalline characteristics,but they still present superior superconductivity.The 3.0-nm-thick film has the superconducting transition temperature of 5.38 K,and its electrical performances follow truly 2D superconducting transitions.This study will not only exhibit a robust superconductingη-Mo3C2 ultrathin film,but also provides a convenient growth way to realize more carbide-based heterostructures for future device applications.展开更多
The output characteristics of neodymium-doped gadolinium vanadate(Nd:GdVO4) crystals laser with dual c-axis orthogonal gains end-pumped by two fiber-coupled diode lasers are investigated. With two 1 W semiconductor di...The output characteristics of neodymium-doped gadolinium vanadate(Nd:GdVO4) crystals laser with dual c-axis orthogonal gains end-pumped by two fiber-coupled diode lasers are investigated. With two 1 W semiconductor diode lasers pumping, the output power of TEM00 laser is 920 m W, and the optical conversion efficiency is close to 46%. By changing the relative orientations of both Nd:Gd VO4 crystals, the polarization characteristics of laser are varied. In particular, by keeping the c-axes of two Nd:Gd VO4 crystals orthogonal to each other and adjusting two diode pump lasers to operate at the same power level, the completely unpolarized light is obtained.展开更多
基金Project(51101046)supported by the National Natural Science Foundation of ChinaProject(E201446)supported by the Natural Science Foundation of Heilongjiang Province of China+1 种基金Projects(2012M510985,2014T70361)supported by China Postdoctoral Science FoundationProject(LBH-Z12142)supported by the Heilongjiang Postdoctoral Fund,China
文摘Considering both the effects of the interfacial normal velocity dependence of solute segregation and the local nonequilibrium solute diffusion,an extended free dendritic growth model was analyzed.Compared with the predictions from the dendritic model with isosolutal interface assumption,the transition from solutal dendrite to thermal dendrite moves to higher undercoolings,i.e.,the region of undercoolings with solute controlled growth is extended.At high undercoolings,the transition from the mainly thermal-controlled growth to the purely thermal-controlled growth is not sharp as predicted by the isosolute model,but occurs in a range of undercooling,due to both the effects of the interfacial normal velocity dependence of solute segregation and the local nonequilibrium solute diffusion.Model test indicates that the present model can give a satisfactory agreement with the available experimental data for the Ni-0.7% B（mole fraction） alloy.
文摘The mixed P3HT （poly（3-hexylthiophene）） and [6,6]-PCBM （phenyl C61-butyric acid methyl ester） organic thin films were investigated for electronic structure using UV-Vis spectrophotometer and PESA （photo-electron spectroscopy in air）. Furthermore, ESR （electron spin resonance） and AFM （atomic force microscopy） were used to investigate the surface morphology and molecular orientation, respectively. ESR analysis indicated the molecular orientation of the P3HT crystalline in the blend thin films, which the crystalline oriented normal to the substrate with distribution of 35°. AFM images indicated that the surface morphology of P3HT film was affected by the presence of PCBM nanoparticles. Solution-processed OTFTs （organic thin-film transistors） based on P3HT/PCBM blend thin film in a top source-drain contact structure was fabricated, and the electrical characteristics of the devices were also investigated. A unipolar property with p-channel characteristics were obtained in glove box measurement.
文摘Metal-semiconductor field effect transistors (MESFETs) were fabricated on H-terminated polycrystalline diamond.The DC characteristics of the p-channel MESFET showed a maximum drain current density of 204 mA/mm at a gate-source voltage of 6 V,and a maximum transconductance of 20 mS/mm at a gate-source voltage of 1.5 V.The small signal S-parameters of MESFET with 2 100 m gate width and 2 m gate length were measured.An extrinsic cut-off frequency (fT) of 1.7 GHz and the maximum oscillation frequency (fmax) of 2.5 GHz were obtained,which was the first report on diamond MESFETs with RF characteristics in China.
基金the National Key R&D Program of China(2018YFA0305800)the Fundamental Research Funds for the Central Universities(020414380145 and 020414380153)+2 种基金the National Natural Science Foundation of China(11674154,11761131010,51972163,11904163,61974021 and 11525415)the Natural Science Foundation of Jiangsu Province(BK20190010)the Fok Ying-Tong Education Foundation of China(171038)。
文摘Two-dimensional(2D)superconductors have intriguing physical properties and abundant potential applications.Recently,2D superconductingα-Mo2C and facecentered cubic Mo2C have been controllably prepared and they bring new viewpoints to carbon-based superconductivity.Although molybdenum carbides(Mo-Cs)have multiple crystalline stacking orders,there are still few structures reported for the lack of higher energy supply during growth.In this study,we report a two-step vapor deposition method to grow superconducting η-Mo3C2 films with different thicknesses,with the assistance of controllable plasma power.The grownη-Mo3C2 films show polycrystalline characteristics,but they still present superior superconductivity.The 3.0-nm-thick film has the superconducting transition temperature of 5.38 K,and its electrical performances follow truly 2D superconducting transitions.This study will not only exhibit a robust superconductingη-Mo3C2 ultrathin film,but also provides a convenient growth way to realize more carbide-based heterostructures for future device applications.
基金supported by the National Natural Science Foundation of China(No.11104234)
文摘The output characteristics of neodymium-doped gadolinium vanadate(Nd:GdVO4) crystals laser with dual c-axis orthogonal gains end-pumped by two fiber-coupled diode lasers are investigated. With two 1 W semiconductor diode lasers pumping, the output power of TEM00 laser is 920 m W, and the optical conversion efficiency is close to 46%. By changing the relative orientations of both Nd:Gd VO4 crystals, the polarization characteristics of laser are varied. In particular, by keeping the c-axes of two Nd:Gd VO4 crystals orthogonal to each other and adjusting two diode pump lasers to operate at the same power level, the completely unpolarized light is obtained.
