Graphene-based heterostructure is one of the most attractive topics in physics and material sciences due to its intriguing properties and applications. We report the one-step fabrication of a novel graphene/Mo2C heter...Graphene-based heterostructure is one of the most attractive topics in physics and material sciences due to its intriguing properties and applications. We report the one-step fabrication of a novel graphene/Mo2C heterostructure by using chemical vapor deposition（CVD）. The composition and structure of the heterostructure are characterized through energydispersive spectrometer, transmission electron microscope, and Raman spectrum. The growth rule analysis of the results shows the flow rate of methane is a main factor in preparing the graphene/Mo2C heterostructure. A schematic diagram of the growth process is also established. Transport measurements are performed to study the superconductivity of the heterostructure which has potential applications in superconducting devices.展开更多
We investigate undoped GaN and Mg-doped GaN grown by rf plasma-assisted molecular beam epitaxy(MBE)with different Mg concentrations by photoluminescence(PL)at low temperature,Hall-effect and XRD measurements.In the PL...We investigate undoped GaN and Mg-doped GaN grown by rf plasma-assisted molecular beam epitaxy(MBE)with different Mg concentrations by photoluminescence(PL)at low temperature,Hall-effect and XRD measurements.In the PL spectra of lightly Mg-doped GaN films,a low intensity near band edge(NBE)emission and strong donor-acceptor pair(DAP)emission with its phonon replicas are observed.As the Mg concentration is increased,the DAP and NBE bands become weaker and a red shift of these bands is observed in the PL spectra.Yellow luminescence(YL)is observed in heavily Mg-doped GaN.The x-ray diffraction is employed to study the structure of the films.Hall measurement shows that there is a maximum value(3.9×10^(18) cm^(−3))of hole concentration with increasing Mg source temperature for compensation effect.PL spectra of undoped GaN are also studied under N-rich and Ga-rich growth conditions.Yellow luminescences of undoped Ga-rich GaN and heavily Mg-doped GaN are compared,indicating the different origins of the YL bands.展开更多
This study reports the growth of aligned monolayer molybdenum disulfide(MoS2)ribbons on a sapphire substrate via NaOH-assisted chemical vapor deposition.The length of MoS2 ribbon is up to 400μm.The MoS2 ribbon has ex...This study reports the growth of aligned monolayer molybdenum disulfide(MoS2)ribbons on a sapphire substrate via NaOH-assisted chemical vapor deposition.The length of MoS2 ribbon is up to 400μm.The MoS2 ribbon has excellent single crystal properties,a carrier mobility of^150 cm^2V^-1s^-1,and a optical response of 103 mA W^-1 at a wavelength of 550 nm.The growth model of MoS2 ribbons was given.NaOH reacts with MoO3 to form sodium molybdate droplets,which increase the fluidity of the molybdenum source on the substrate,realizing the vapor-liquid-solid growth of MoS2 on sapphire.The monolayer MoS2 ribbons have two kinds of arrangements on the sapphire substrate,one is the oriented growth affected by the interlayer van der Waals force and the lattice,and the other is the aligned growth constrained by the sapphire step.Our results promote the basic research and device applications of MoS2,and introduce a new way of synthesizing other one dimensional(1D)and 2D nanostructures.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.1402342,11574338,and 11274333)the Hundred Talents Program of Chinese Academy of Sciences,the International Collaboration and Innovation Program on High Mobility Materials Engineering,Chinese Academy of Sciences(Grant No.KGZD-EW-303)the“Strategic Priority Research Program(B)”of the Chinese Academy of Sciences(Grant No.XDB04040300)
文摘Graphene-based heterostructure is one of the most attractive topics in physics and material sciences due to its intriguing properties and applications. We report the one-step fabrication of a novel graphene/Mo2C heterostructure by using chemical vapor deposition（CVD）. The composition and structure of the heterostructure are characterized through energydispersive spectrometer, transmission electron microscope, and Raman spectrum. The growth rule analysis of the results shows the flow rate of methane is a main factor in preparing the graphene/Mo2C heterostructure. A schematic diagram of the growth process is also established. Transport measurements are performed to study the superconductivity of the heterostructure which has potential applications in superconducting devices.
基金by the Fundamental Research Funds for the Central Universitiesthe National Natural Science Foundation of China under Grant No 60876011.
文摘We investigate undoped GaN and Mg-doped GaN grown by rf plasma-assisted molecular beam epitaxy(MBE)with different Mg concentrations by photoluminescence(PL)at low temperature,Hall-effect and XRD measurements.In the PL spectra of lightly Mg-doped GaN films,a low intensity near band edge(NBE)emission and strong donor-acceptor pair(DAP)emission with its phonon replicas are observed.As the Mg concentration is increased,the DAP and NBE bands become weaker and a red shift of these bands is observed in the PL spectra.Yellow luminescence(YL)is observed in heavily Mg-doped GaN.The x-ray diffraction is employed to study the structure of the films.Hall measurement shows that there is a maximum value(3.9×10^(18) cm^(−3))of hole concentration with increasing Mg source temperature for compensation effect.PL spectra of undoped GaN are also studied under N-rich and Ga-rich growth conditions.Yellow luminescences of undoped Ga-rich GaN and heavily Mg-doped GaN are compared,indicating the different origins of the YL bands.
基金financially supported by the Science and Technology Commission of Shanghai Municipality(20501130200)the National Natural Science Foundation of China(51402342 and 61775201)the National Defense Technology Innovation Special Zone Project.
基金This work was financially supported by the Science and Technology Commission of Shanghai Municipality(18511110700).
文摘This study reports the growth of aligned monolayer molybdenum disulfide(MoS2)ribbons on a sapphire substrate via NaOH-assisted chemical vapor deposition.The length of MoS2 ribbon is up to 400μm.The MoS2 ribbon has excellent single crystal properties,a carrier mobility of^150 cm^2V^-1s^-1,and a optical response of 103 mA W^-1 at a wavelength of 550 nm.The growth model of MoS2 ribbons was given.NaOH reacts with MoO3 to form sodium molybdate droplets,which increase the fluidity of the molybdenum source on the substrate,realizing the vapor-liquid-solid growth of MoS2 on sapphire.The monolayer MoS2 ribbons have two kinds of arrangements on the sapphire substrate,one is the oriented growth affected by the interlayer van der Waals force and the lattice,and the other is the aligned growth constrained by the sapphire step.Our results promote the basic research and device applications of MoS2,and introduce a new way of synthesizing other one dimensional(1D)and 2D nanostructures.
