A two-dimensional solution of space-charge-limiting current for a high current vacuum diode with a spherical cathode is presented. The relation between space-charge-limiting current and electric field enhancement fact...A two-dimensional solution of space-charge-limiting current for a high current vacuum diode with a spherical cathode is presented. The relation between space-charge-limiting current and electric field enhancement factor at the cathode surface for the diode with a curved surface cathode is also discussed. It is shown that compared with the current given by the conventional Child-Langmuir law, which describes the one-dimensional space-charege-limiting current, the two-dimensional space-charge-limiting current in such a diode is enhanced due to the electric-field enhancement along the cathode surface. Among practical parameter ranges, enhancement factor ηb approximately satisfies ηb Aβn, where β is the electric field enhancement factor at the cathode surface, and n is a constant between 1 and 2, which is confirmed to be universal for the diodes with curved surface cathodes.展开更多
Numerical solutions to floating plasma potentials for walls emitting secondary elec- trons are obtained for various surface materials. The calculations are made with plasma moment equations and the secondary electron ...Numerical solutions to floating plasma potentials for walls emitting secondary elec- trons are obtained for various surface materials. The calculations are made with plasma moment equations and the secondary electron emission coefficients, which were determined from recent laboratory experiments. The results estimate the wall potentials up to the physical conditions that allow stable plasma sheaths under the space-charge-limited condition. The materials often used in the laboratory, such as aluminum, silicon, boron, molybdenum, silicon dioxide, and alumina, are considered. The minimum wall potential before the onset of space-charge-limited emission is determined by the electron temperatures at which the effective secondary electron emission coefficient integrated over the velocity distributions is about 0.62. The corresponding potential is given by -eφ0 ,- 1.87kBT. The condition for space-charge-limited emission is newly found by numerically searching for all the stable sheaths. The new condition is -eφ0 - 0.95kBT, and this predicts a wall potential that is less negative than the previously found one. Calculation of the power dissipated to the wall for hydrogen plasmas shows that there is a large difference in terms of power dissipation among the considered materials in the temperature range 20-50 eV.展开更多
The article theoretically studied the charge-exchange effects on space charge limitedelectron and ion current densities of non-relativistic one-dimensional slab ion diode, and comparedwith those of without charge exch...The article theoretically studied the charge-exchange effects on space charge limitedelectron and ion current densities of non-relativistic one-dimensional slab ion diode, and comparedwith those of without charge exchange.展开更多
The(001)oriented BiFeO_(3)thin film was deposited on the Nb:SrTiO_(3)substrate by radio frequency magnetron sputtering technology,and the bipolar resistive switching effect was observed in the BiFeO_(3)/Nb:SrTiO_(3)he...The(001)oriented BiFeO_(3)thin film was deposited on the Nb:SrTiO_(3)substrate by radio frequency magnetron sputtering technology,and the bipolar resistive switching effect was observed in the BiFeO_(3)/Nb:SrTiO_(3)heterostructure.The results showed that the ratio between the high resistance and low resistance was more than two orders at a reading pulse of-0.5 V and it exhibited excellent retention over 3600 s.The current density-voltage characteristic was dominated by the space-charge-limited conduction.The resistive switching effect of the structure was attributed to the trapping/detrapping of the charge carriers.展开更多
A Bi2Sr2Co2Oy/Si heterojunction is obtained by growing a layer of p-type oxygen-deficient Bi2Sr2Co2Oy film on a commercial n-type silicon wafer by pulsed laser deposition. Its rectifying and photovoltaic properties ar...A Bi2Sr2Co2Oy/Si heterojunction is obtained by growing a layer of p-type oxygen-deficient Bi2Sr2Co2Oy film on a commercial n-type silicon wafer by pulsed laser deposition. Its rectifying and photovoltaic properties are studied in a wide temperature range from 20 K to 300 K. The transport mechanism under the forward bias can be attributed to a trap- filled space-charge-limited current conduction mechanism. Under the irradiation of a 532-nm continuous wave laser, a clear photovoltaic effect is observed and the magnitude ofphotovoltage increases as the temperature decreases, The results demonstrate the potential application of a Bi2SrzCo2Oy-based heterojunction in the photoelectronic devices.展开更多
The transmission-line-circuit model of the Z accelerator, developed originally by W. A. STYGAR, P. A. CORCORAN, et al., is revised. The revised model uses different calculations for the electron loss and flow impedanc...The transmission-line-circuit model of the Z accelerator, developed originally by W. A. STYGAR, P. A. CORCORAN, et al., is revised. The revised model uses different calculations for the electron loss and flow impedance in the magnetically insulated transmission line system of the Z accelerator before and after magnetic insulation is established. By including electron pressure and zero electric field at the cathode, a closed set of equations is obtained at each time step, and dynamic shunt resistance （used to represent any electron loss to the anode） and flow impedance are solved, which have been incorporated into the transmission line code for simulations of the vacuum section in the Z accelerator. Finally, the results are discussed in comparison with earlier findings to show the effectiveness and limitations of the model.展开更多
By considering the interaction between Fowler-Nordheim tunneling injection theory and charge carriers transporting through the bulk, an electroluminescence model for organic single-layer diodes is presented. The expre...By considering the interaction between Fowler-Nordheim tunneling injection theory and charge carriers transporting through the bulk, an electroluminescence model for organic single-layer diodes is presented. The expressions of the recombination current density, recombination efficiency and conductivity of the diodes are provided, which elucidate the controlling role of the electric field on mobility and recombination zone. The equilibrium of two opposite charge carriers injection and the cen-tral position of recombination zone are two important preconditions for reducing the leakage current. Space-charge-limited current occurs only over a certain high bias, meanwhile, the quantity of injection carriers increases over the transport capacity of the bulk.展开更多
文摘A two-dimensional solution of space-charge-limiting current for a high current vacuum diode with a spherical cathode is presented. The relation between space-charge-limiting current and electric field enhancement factor at the cathode surface for the diode with a curved surface cathode is also discussed. It is shown that compared with the current given by the conventional Child-Langmuir law, which describes the one-dimensional space-charege-limiting current, the two-dimensional space-charge-limiting current in such a diode is enhanced due to the electric-field enhancement along the cathode surface. Among practical parameter ranges, enhancement factor ηb approximately satisfies ηb Aβn, where β is the electric field enhancement factor at the cathode surface, and n is a constant between 1 and 2, which is confirmed to be universal for the diodes with curved surface cathodes.
基金supported partially by the National Space Lab(No.2009-0091569)BK21+ program through the National Research Foundation(NRF)funded by the Ministry of Education of Korea
文摘Numerical solutions to floating plasma potentials for walls emitting secondary elec- trons are obtained for various surface materials. The calculations are made with plasma moment equations and the secondary electron emission coefficients, which were determined from recent laboratory experiments. The results estimate the wall potentials up to the physical conditions that allow stable plasma sheaths under the space-charge-limited condition. The materials often used in the laboratory, such as aluminum, silicon, boron, molybdenum, silicon dioxide, and alumina, are considered. The minimum wall potential before the onset of space-charge-limited emission is determined by the electron temperatures at which the effective secondary electron emission coefficient integrated over the velocity distributions is about 0.62. The corresponding potential is given by -eφ0 ,- 1.87kBT. The condition for space-charge-limited emission is newly found by numerically searching for all the stable sheaths. The new condition is -eφ0 - 0.95kBT, and this predicts a wall potential that is less negative than the previously found one. Calculation of the power dissipated to the wall for hydrogen plasmas shows that there is a large difference in terms of power dissipation among the considered materials in the temperature range 20-50 eV.
文摘The article theoretically studied the charge-exchange effects on space charge limitedelectron and ion current densities of non-relativistic one-dimensional slab ion diode, and comparedwith those of without charge exchange.
基金Funded by the National Natural Science Foundation of China(Nos.61201046 and 61306057)the Beijing Natural Science Foundation of China(Nos.4162013,2132023 and 4164082)+2 种基金the Beijing Postdoctoral Research Foundation(No.2015ZZ-33)the Scientific Research Project of Beijing Educational Committee(No.KM201610005005)the Scientific Research Foundation for Returned Overseas Chinese Scholars,State Education Ministry
文摘The(001)oriented BiFeO_(3)thin film was deposited on the Nb:SrTiO_(3)substrate by radio frequency magnetron sputtering technology,and the bipolar resistive switching effect was observed in the BiFeO_(3)/Nb:SrTiO_(3)heterostructure.The results showed that the ratio between the high resistance and low resistance was more than two orders at a reading pulse of-0.5 V and it exhibited excellent retention over 3600 s.The current density-voltage characteristic was dominated by the space-charge-limited conduction.The resistive switching effect of the structure was attributed to the trapping/detrapping of the charge carriers.
基金Project supported by the National Basic Research Program of China (Grant No.2011CB612305)the National Natural Science Foundation of China (Grant No.51372064)+1 种基金the One Hundred Persons Project of Hebei Province of China (Grant No.CPRC001)the Science and Technology Research Project of Colleges and Universities in Hebei Province,China (Grant No.QN20131040)
文摘A Bi2Sr2Co2Oy/Si heterojunction is obtained by growing a layer of p-type oxygen-deficient Bi2Sr2Co2Oy film on a commercial n-type silicon wafer by pulsed laser deposition. Its rectifying and photovoltaic properties are studied in a wide temperature range from 20 K to 300 K. The transport mechanism under the forward bias can be attributed to a trap- filled space-charge-limited current conduction mechanism. Under the irradiation of a 532-nm continuous wave laser, a clear photovoltaic effect is observed and the magnitude ofphotovoltage increases as the temperature decreases, The results demonstrate the potential application of a Bi2SrzCo2Oy-based heterojunction in the photoelectronic devices.
基金supported by National Natural Science Foundation of China (No. 50637010)
文摘The transmission-line-circuit model of the Z accelerator, developed originally by W. A. STYGAR, P. A. CORCORAN, et al., is revised. The revised model uses different calculations for the electron loss and flow impedance in the magnetically insulated transmission line system of the Z accelerator before and after magnetic insulation is established. By including electron pressure and zero electric field at the cathode, a closed set of equations is obtained at each time step, and dynamic shunt resistance （used to represent any electron loss to the anode） and flow impedance are solved, which have been incorporated into the transmission line code for simulations of the vacuum section in the Z accelerator. Finally, the results are discussed in comparison with earlier findings to show the effectiveness and limitations of the model.
基金This work was financed by the National Natural Science Foundation of China (Grant Nos. 29992530 and 19974002) the Paper Foundation of Northern Jiaotong University.
文摘By considering the interaction between Fowler-Nordheim tunneling injection theory and charge carriers transporting through the bulk, an electroluminescence model for organic single-layer diodes is presented. The expressions of the recombination current density, recombination efficiency and conductivity of the diodes are provided, which elucidate the controlling role of the electric field on mobility and recombination zone. The equilibrium of two opposite charge carriers injection and the cen-tral position of recombination zone are two important preconditions for reducing the leakage current. Space-charge-limited current occurs only over a certain high bias, meanwhile, the quantity of injection carriers increases over the transport capacity of the bulk.
