A first principles study of the electronic properties and bulk modulus （B0） of the fcc and bcc transition metals, transition metal carbides and nitrides is presented. The calculations were performed by plane-wave ps...A first principles study of the electronic properties and bulk modulus （B0） of the fcc and bcc transition metals, transition metal carbides and nitrides is presented. The calculations were performed by plane-wave pseudopotential method in the framework of the density functional theory with local density approximation. The density of states and the valence charge densities of these solids are plotted. The results show that B0 does not vary monotonically when the number of the valence d electrons increases. B0 reaches a maximum and then decreases for each of the four sorts of solids. It is related to the occupation of the bonding and anti-bonding states in the solid. The value of the valence charge density at the midpoint between the two nearest metal atoms tends to be proportional to B0.展开更多
InFeP layers are prepared by ion implantation of InP with 100-keV Fe＋ ions to a dose of 5 ×10^16 cm-2 and investigated by optical, magnetic, and ion beam analysis measurements. Photoluminescence measurements sho...InFeP layers are prepared by ion implantation of InP with 100-keV Fe＋ ions to a dose of 5 ×10^16 cm-2 and investigated by optical, magnetic, and ion beam analysis measurements. Photoluminescence measurements show a deep-level peak at 1.035 eV due to Fe in InP and two exciton-related luminescences at 1.426 eV and 1.376 eV in the implanted samples annealed at 400℃. Conversion electron Mossbauer spectroscopy reveals a doublet corresponding to Fe3＋ ions in the indium sites. Atomic force microscopy and magnetic force microscopy show that magnetic clusters are formed in the annealing process. The magnetization-field hysteresis loops show ferromagnetic properties persisting up to room temperature with a coercive field of 100 0e （10e = 79.5775 A-m-1）, saturation magnetization of 4.35 × 10-5 emu, and remnant magnetization of 4.4× 10 6 emu.展开更多
ZnO：Cr layer was prepared by Cr ion implantation into ZnO bulk crystals. The structural, optical, and magnetic properties of the ZnO：Cr layer were studied with X-ray diffraction, photoluminescence, and superconducto...ZnO：Cr layer was prepared by Cr ion implantation into ZnO bulk crystals. The structural, optical, and magnetic properties of the ZnO：Cr layer were studied with X-ray diffraction, photoluminescence, and superconductor quantum interferometer, respectively. The ZnO：Cr layer implanted Cr with a dose of 5 10 16 cm 2 remained wurtzite structure and exhibited near-band-edge photoluminescence at 3.365 eV with full-width at half-maximum of 8.4 meV at 10 K. The magnetic measurement showed that the ferromagnetism changed at room temperature by different Cr concentration. For samples implanted to high doses, remanent magnetization reached 1.805 10 -4 emu/g and coercive field was 244.5 Oe. Hall effect measurement showed a decrease of the resistivity from 251.7 cmto 28.6 cmafter annealing at 800 ℃. The magnetism is interpreted by bound magnetic polarons, which were taken into account of the process that electrons were locally trapped by oxygen vacancies and occupied the orbitals that overlapped with d shell of neighboring Cr ions.展开更多
A computer-automated Rutherford backscattering/channeling （RBS/C） system is developed to provide in situ ion beam analysis of the accelerator-TEM system in Wuhan University. The basic system components are a PC equi...A computer-automated Rutherford backscattering/channeling （RBS/C） system is developed to provide in situ ion beam analysis of the accelerator-TEM system in Wuhan University. The basic system components are a PC equipped with a multichannel analyzer data acquisition board, motion control hardware including the Panmure stepping motor controller and integrated circuit modules, and a Labview programmed operating system with associated electronics. Single crystalline Si（001） and ZnO（001） implanted with Mn ions were characterized with this computerized setup. The crystalline quality Xmin and channeling half angle of Si（O01） were measured to be 4.65% and 0.52%, respectively, which are comparable to theoretical values 4.2% and 0.32%. The ion implantation induced damage depth profile derived from channeling and random spectrum is in reasonable agreement with the result calculated by the SRIM Monte-Carlo simulation code.展开更多
Memristive heterostructures,composed of reduced graphene oxide with different degree of reduction,were demonstrated through a simple method of‘direct electron-beam writing’on graphene oxide.Irradiation with an elect...Memristive heterostructures,composed of reduced graphene oxide with different degree of reduction,were demonstrated through a simple method of‘direct electron-beam writing’on graphene oxide.Irradiation with an electron beam at various doses and accelerating voltages made it possible to define highand low-conductivity graphene-oxide areas.The electron beam-reduced graphene oxide/graphene oxide heterostructure clearly exhibited a nonlinear behavior and a well-controlled resistive switching characteristic at a low operating-voltage range(<1 V).The proposed memristive heterostructures are promising for highly-efficient digital storage and information process as well as for analogous neuromorphic computations.展开更多
We have developed a computerized system for measuring field electron emission （FE） and field ionization （FI）, which has a three-electrode configuration with emitters biased up to 25 kV, and is programmed by the La...We have developed a computerized system for measuring field electron emission （FE） and field ionization （FI）, which has a three-electrode configuration with emitters biased up to 25 kV, and is programmed by the Labview software. The current-voltage curves of nano-tip tungsten and carbon nanotube （CNT） arrays were measured. The electron emission of CNTs proceeded with a turn-on field of 1.24 V/μm and a threshold field of 1.85 V/μm. Compared to the field emission, field ionization turned on at 3.5 V/μm. Raman spectroscopy and scanning electron microscopy （SEM） measurements showed degradation of the CNTs after FE/FI testing. The measurement of a W-tip revealed strong electron emission and instability behavior at a field strength higher than 7.0 V/μm.展开更多
The M-V wide band gap semiconductors show the potential in applications for dilute magnetic semiconductors.AIN films are implanted with 20-keV Mn^(+)ions with a dose of 5 x 10^(6)cm^(-2).The cross section of as-implan...The M-V wide band gap semiconductors show the potential in applications for dilute magnetic semiconductors.AIN films are implanted with 20-keV Mn^(+)ions with a dose of 5 x 10^(6)cm^(-2).The cross section of as-implanted AIN are investigated by field-emission scanning electron microscopy and the energy dispersive spectra.The result confirms that the implantation depth is about 100nm.Cathodoluminescence measurements show the main peak at 2.6eV attributed to a donor-to-Mn²+transition.It is argued that the Mn element in AIN can act as a p-type dopant peak at 2.07eV.The magnetic measurement shows a transition temperature of 100K in the implanted AIN annealed at 500℃for 30 min.Clear ferromagnetic hysteresis was observed at 77K,with a coercive field of 212.7Oe.展开更多
Polycrystalline CdMnS and CdMnS：Au films with hexagonal structure on Si（111） substrates are prepared by co-evaporation, and exhibit ferroelectric and ferromagnetic properties, respectively. Under optimized growth c...Polycrystalline CdMnS and CdMnS：Au films with hexagonal structure on Si（111） substrates are prepared by co-evaporation, and exhibit ferroelectric and ferromagnetic properties, respectively. Under optimized growth conditions, CdMnS：Au samples with an average crystallite size of 90nm and Mn concentration of 5.0at.% are obtained, and an all-semiconductor spin valve device of Co/Au/CdMnS：Au/CdMnS/Pt is fabricated. Electrical measurement of the device reveals the clear dependence of resistance on applied magnetic field, with a relative magnetoresistance of 0.06% and a switching field of 100 Oe at 77K.展开更多
基金Project supported by the National Natural Science Foundation of China （Grant Nos 50175082 and 10275049）, and the Fund for the Doctoral Program of Higher Education （Grant No 2002486016）.
文摘A first principles study of the electronic properties and bulk modulus （B0） of the fcc and bcc transition metals, transition metal carbides and nitrides is presented. The calculations were performed by plane-wave pseudopotential method in the framework of the density functional theory with local density approximation. The density of states and the valence charge densities of these solids are plotted. The results show that B0 does not vary monotonically when the number of the valence d electrons increases. B0 reaches a maximum and then decreases for each of the four sorts of solids. It is related to the occupation of the bonding and anti-bonding states in the solid. The value of the valence charge density at the midpoint between the two nearest metal atoms tends to be proportional to B0.
基金Project supported by the International Cooperation Program of the Ministry of Science and Technology,China(Grant No.2011DFR50580)the Fundamental Research Funds for the Central Universities,China(Grant No.20102020101000022)
文摘InFeP layers are prepared by ion implantation of InP with 100-keV Fe＋ ions to a dose of 5 ×10^16 cm-2 and investigated by optical, magnetic, and ion beam analysis measurements. Photoluminescence measurements show a deep-level peak at 1.035 eV due to Fe in InP and two exciton-related luminescences at 1.426 eV and 1.376 eV in the implanted samples annealed at 400℃. Conversion electron Mossbauer spectroscopy reveals a doublet corresponding to Fe3＋ ions in the indium sites. Atomic force microscopy and magnetic force microscopy show that magnetic clusters are formed in the annealing process. The magnetization-field hysteresis loops show ferromagnetic properties persisting up to room temperature with a coercive field of 100 0e （10e = 79.5775 A-m-1）, saturation magnetization of 4.35 × 10-5 emu, and remnant magnetization of 4.4× 10 6 emu.
基金Supported by the National Natural Science Foundation of China(11075121)the International Cooperation Program of Ministry of Science and Technology of China(2010DFA02010)
文摘ZnO：Cr layer was prepared by Cr ion implantation into ZnO bulk crystals. The structural, optical, and magnetic properties of the ZnO：Cr layer were studied with X-ray diffraction, photoluminescence, and superconductor quantum interferometer, respectively. The ZnO：Cr layer implanted Cr with a dose of 5 10 16 cm 2 remained wurtzite structure and exhibited near-band-edge photoluminescence at 3.365 eV with full-width at half-maximum of 8.4 meV at 10 K. The magnetic measurement showed that the ferromagnetism changed at room temperature by different Cr concentration. For samples implanted to high doses, remanent magnetization reached 1.805 10 -4 emu/g and coercive field was 244.5 Oe. Hall effect measurement showed a decrease of the resistivity from 251.7 cmto 28.6 cmafter annealing at 800 ℃. The magnetism is interpreted by bound magnetic polarons, which were taken into account of the process that electrons were locally trapped by oxygen vacancies and occupied the orbitals that overlapped with d shell of neighboring Cr ions.
基金Supported by the National Natural Science Foundation of China under Grant No 10875091.
文摘A computer-automated Rutherford backscattering/channeling （RBS/C） system is developed to provide in situ ion beam analysis of the accelerator-TEM system in Wuhan University. The basic system components are a PC equipped with a multichannel analyzer data acquisition board, motion control hardware including the Panmure stepping motor controller and integrated circuit modules, and a Labview programmed operating system with associated electronics. Single crystalline Si（001） and ZnO（001） implanted with Mn ions were characterized with this computerized setup. The crystalline quality Xmin and channeling half angle of Si（O01） were measured to be 4.65% and 0.52%, respectively, which are comparable to theoretical values 4.2% and 0.32%. The ion implantation induced damage depth profile derived from channeling and random spectrum is in reasonable agreement with the result calculated by the SRIM Monte-Carlo simulation code.
基金supported financially by the Russian Foundation of Basic Research(Nos.19-29-03050 and 18-29-19120)the National Research Foundation of Korea(Nos.2016R1A6A1A03012877,2017R1D1A1B03035102 and 2017R1A2B4004281).
文摘Memristive heterostructures,composed of reduced graphene oxide with different degree of reduction,were demonstrated through a simple method of‘direct electron-beam writing’on graphene oxide.Irradiation with an electron beam at various doses and accelerating voltages made it possible to define highand low-conductivity graphene-oxide areas.The electron beam-reduced graphene oxide/graphene oxide heterostructure clearly exhibited a nonlinear behavior and a well-controlled resistive switching characteristic at a low operating-voltage range(<1 V).The proposed memristive heterostructures are promising for highly-efficient digital storage and information process as well as for analogous neuromorphic computations.
基金supported by National Natural Science Foundation(No.11075121)the International Science and Technology Cooperation Program(No.2010DFA02010)Three Gorges University of China(KJ2009B011)
文摘We have developed a computerized system for measuring field electron emission （FE） and field ionization （FI）, which has a three-electrode configuration with emitters biased up to 25 kV, and is programmed by the Labview software. The current-voltage curves of nano-tip tungsten and carbon nanotube （CNT） arrays were measured. The electron emission of CNTs proceeded with a turn-on field of 1.24 V/μm and a threshold field of 1.85 V/μm. Compared to the field emission, field ionization turned on at 3.5 V/μm. Raman spectroscopy and scanning electron microscopy （SEM） measurements showed degradation of the CNTs after FE/FI testing. The measurement of a W-tip revealed strong electron emission and instability behavior at a field strength higher than 7.0 V/μm.
基金Supported by the National Natural Science Foundation of China under Grant Nos 50175082 and 10275049the Fund for Doctoral Programme of Higher Education of China under Grant No 2002486016partially the Korea Science and Engineering Foundation from the Quantum Functional Research Center at Dongguk University.
文摘The M-V wide band gap semiconductors show the potential in applications for dilute magnetic semiconductors.AIN films are implanted with 20-keV Mn^(+)ions with a dose of 5 x 10^(6)cm^(-2).The cross section of as-implanted AIN are investigated by field-emission scanning electron microscopy and the energy dispersive spectra.The result confirms that the implantation depth is about 100nm.Cathodoluminescence measurements show the main peak at 2.6eV attributed to a donor-to-Mn²+transition.It is argued that the Mn element in AIN can act as a p-type dopant peak at 2.07eV.The magnetic measurement shows a transition temperature of 100K in the implanted AIN annealed at 500℃for 30 min.Clear ferromagnetic hysteresis was observed at 77K,with a coercive field of 212.7Oe.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10875090 and 10875091, and by the Korean Science and Engineering Foundation through QSRC at Dongguk University.
文摘Polycrystalline CdMnS and CdMnS：Au films with hexagonal structure on Si（111） substrates are prepared by co-evaporation, and exhibit ferroelectric and ferromagnetic properties, respectively. Under optimized growth conditions, CdMnS：Au samples with an average crystallite size of 90nm and Mn concentration of 5.0at.% are obtained, and an all-semiconductor spin valve device of Co/Au/CdMnS：Au/CdMnS/Pt is fabricated. Electrical measurement of the device reveals the clear dependence of resistance on applied magnetic field, with a relative magnetoresistance of 0.06% and a switching field of 100 Oe at 77K.
