非晶硅碳薄膜发光二极管发光的热致猝灭

本文详细测试了用RF-PECVD法制备的非晶硅碳薄膜发光二极管的光强电流特性和温度对器件发光强度的影响.在直流电流驱动下,器件的发光在注入电流1A/cm2左右趋于饱和,而在低占空比的脉冲电流驱动下器件的发光直至注入电流20A/cm2仍随电流近似线性增长,但提高环境温度发光随之下降.结合对器件受热情况分析表明,热致猝灭而非场致猝灭导致了器件在大电流下的发光饱和,并简要提出了改进器件散热的措施.     

High Performance, Low Energy Ion Source

An ion accelerator system using one or two fine mesh tungsten grids has been used in a magnetic multipole containment ion source to produce a continuous positive ion beam variable over a wide range of beam currents and accelerator voltages. The ion source plasma is low noise and uniform to ± 1% density variation over 9 cm diameter. Beams up to 4 cm × 4 cm have been extracted which have low divergence (±1%), uniform current density (±2%), small ion energy speed, beam ion energy variable from 200V to several thousand volts, and current densities variable from ?A per cm2 to tens of milliamperes per cm2, limited only by acceleration grid power loading or sputtering.     

The Jon Beam Opening Switch

Plasma opening switches (POS's) have shown excellent characteristics in pulsed power applications. Proposed POS scaling predicts that the fastest opening time for a given conducted current should occur using a high-velocity low-density plasma as the switch medium. The ion beam opening switch (IBOS) uses a charge-neutral ion beam of 100-300 kV, ? 120 A/cm2 as the switch "plasma." Its velocity of up to 600 cm/?s and density of ~1012/cm3 make this a very fast low-density plasma compared with typical 10 cm/?s and 1013/cm3 POS plasmas. The IBOS has conducted ? 70 kA flowing in a parallel-plate transmission line driven by a 4-? pulser. IBOS opening time is load dependent, being ? 4 ns into a 15-nH load and about twice as long into a 4-? electron diode load. However, switch impedance is not zero during the entire conduction time, rising to ? 3 ? by the time of peak current. Peak current conducted before opening does not vary linearly with either injected ion current or switch axial length. Instead, the conduction current scales with plasma density in the switch, and is nearly independent of switch area until the area is restricted to a narrow (~1 cm) strip.     

Generation of High-Current Low-Energy Electron Beams in Systems with Plasma Emitters

Generation and transport of high-current electron beams are investigated in gas-filled diodes with plasma emitters based on arc and glow discharges. A space-charge neutralized beam with a current up to 1 kA was produced in a diode with a plasma emitter based on an arc discharge for an accelerating voltage of 15 kV. The beam is constricted from 8 cm down to 1 cm in diameter by a self-magnetic field and is transported through a distance of over 20 cm with an efficiency of 70%. A beam with a current of 80 A and a current density up to 100 A/cm² was produced in a glow-discharge diode. The beam was transported through a distance of 30 cm in a weak axial magnetic field with induction B = 0.015 T.     

Hot electrons in silicon dioxide: Ballistic to steady-state transport

Hot electron transport in silicon dioxide is examined with emphasis on current experimental and theoretical results. For oxide layers thicker than 100 Å, steady-state transport has been shown to control the carrier flow at all fields studied. The transition from a nearly thermal electron distribution at electric fields less than approximately 1.5 MV/cm to significantly hot distributions with average energies between 2 and 6 eV at higher fields of up to 16 MV/cm is discussed. The significance of nonpolar phonon scattering in controlling the dispersive transport at higher electric fields, thereby preventing runaway and avalanche breakdown, is reviewed. The transition from ballistic to steady-state transport on very thin oxides layers of less than 100 Å in thickness and the observation of single phonon scattering events are also discussed.     

Experimental study of a saturated multipactor in crossed fields

We propose an experimental scheme of and develop a method for studying a one-sided multipactor discharge in crossed fields in the saturation regime. Basic parameters of the discharge have been measured. In the experiment performed in a 3-cm wavelength band, the discharge develops in microwave fields with intensities from 8 kV/cm (near the lower threshold) to 20 kV/cm and became stabilized during at least a hundred cycles of multiplication of secondary electrons on the discharge surface. In this case, the maximum power absorbed in the discharge amounts up to 4 kW/cm², and the corresponding density of the saturated-discharge current, up to 10 A/cm². The measured time of discharge development is equal to 15–30 ns. These parameters agree well with estimating calculations based on approximate analytical models.     

Electron beam extraction from a broad-beam vacuum-arc metal plasmasource

We describe experiments demonstrating the formation of a high current electron beam from a vacuum arc plasma. A preexisting vacuum arc ion source was used, with the extraction voltage reversed in polarity so as to form an electron beam rather than an ion beam; no other changes were required. The beam formed was of energy up to 33 keV, beam current up to 70 A, beam diameter about 10 cm, pulse width 500 μs, and energy density up to 25 J/cm². This kind of source can be used for material surface modification     

Dispersion and transport of energetic particles due to the interaction of intense laser pulses with overdense plasmas

We study the angular distribution of relativistic electrons generated through laser-plasma interaction with pulse intensity varying from 10(18) W/cm2 up to 10(21) W/cm2 and plasma density ranging from 10 times up to 160 times critical density with the help of 2D and 3D particle-in-cell simulations. This study gives clear evidence that the divergence of the beam is an intrinsic property of the interaction of a laser pulse with a sharp density gradient. It is entirely due to the excitation of large static magnetic fields in the layer of interaction. The energy deposited in this layer increases drastically the temperature of the plasma independently of the initial temperature. This makes the plasma locally collisionless and the simulation relevant for the current experiments.     

Self-field AC losses of textured Bi2Sr2CaCu2O8+δ thin rods

Self-field AC losses of polycrystalline Bi-2212 thin rods textured by a Laser Floating Zone (LFZ) melting technique have been measured at 77 K. With the optimal processing parameters, these rods, of 1.6–2 mm diameter and 10 cm length, have a transport critical current density of 3 kA/cm² in the self-field which decreases to about 1.5 kA/cm² in fields of 0.02 T applied perpendicular to the rod axis. The self-field AC losses have been measured in DC magnetic fields up to 0.03 T. The measurements in zero field show that for a large current range the losses are dominated by hysteresis losses as described by the Critical State Model for a cylinder. For the measurements in DC fields the losses show an increasingly resistive-like dependence with current, while the hysteretic component expected from the CSM becomes less important. Measurements at different frequencies also indicated that the loss per cycle in fields is strongly frequency dependent.     

SMIS75金属离子的多重电离

A Simple Mirror Ion Source with 75GHz pumping(SMIS 75)has been created.The confinement system is a mirror trap with magnetic field in the plug up to 5T,variable length 15—20cm and mirror ratio 3—5.The plasma of metal ions is injected into the trap by a special vacuum arc minigun.Plasma heating is performed by the microwave radiation of a gyrotron(the frequency of 75GHz,power up to 200kW,pulse duration up to 150μs).The results of the experiment have demonstrated substantial multiple ionization of metal ions.For a metal with high melting temperature(Pt),heating shifts the average ion charge from Pt~(2 ) up to Pt~(7 ).Maximum stripped observed ion is Pt~(10 ).Total current of ion beam is about 300mA.     

MgB2薄膜的制备与特殊性质

本文报道了利用混合物理化学气相沉积方法(HPCVD)在SiC衬底上制备出约150 nm厚,结构均匀的MgB2薄膜.由R~T曲线知道样品TC(0)高达40.1K.由M~T曲线知道其TC=40.4K,且曲线转变十分陡峭.X射线衍射分析表明薄膜具有较好的C轴取向,没有氧污染,却存在Mg的杂峰.由M~H曲线,利用毕恩模型计算得到了5 K零场条件下JC(0T,5K)=2.7×106A/cm2,Hc2=19.5 T.这些结果表明过量的Mg对MgB2薄膜的转变温度以及有些性质有较大的影响.     

Study of current drain during electrochemical etching of polycarbonate detectors

Polycarbonate (PC) detector is one of the common detectors for neutron and radon gas detection. Using this detector it is possible to measure the dose in mSv, by counting tracks/cm² on an etched surface. In this paper, a special procedure has been suggested to determine the dose based on current drain during the etching process. In these experiments the effects of voltage, frequency, effective etched area, PC detector's thickness, etched area (one side or two sides), etching solution temperature and dose absorbed by the PC foil have been studied.The results obtained show the current drain variation for a voltage of 200–1600 V, a frequency of 2–10 kHz, effective area with a diameter of 2–12 cm, PC thickness of 125–250–375– and a temperature of etching solution of 25–.Lexan PC foils were exposed to doses of of neutrons. The unexposed foils were considered as the background (BG) foils. Most of the experiments were performed at a voltage of 800 V, a frequency of 2 and 8 kHz, foil thickness of , diameter of effective etched area of foils of 2, 6 and 12 cm, temperatures of 25 and and the etching process from 0 up to overload stage. Overload stage occurs when the foil becomes so thin due to growth of the tracks that it leads to sparking between phase and null that makes a hole in the foil.Current drain curves versus the function of the etching time are absolutely different for various doses from zero (BG) to 10 rad (BG up to ). This is true especially for the time interval from 3 h of etching up to overload stage. In this way, it is possible to obtain a calibration of PC detector net current drain based on its absorbed dose.In this experiment, the number and diameter of tracks and their relation with drain current and PC foil residual thickness at overload stage have been studied.The same experiment has been performed for various concentrations of radon gas (Bq/m3) as well.     

由窄带隙芴基共聚物制备的有效光伏电池

对基于9, 9-二辛基取代芴与4, 7-二硒吩-2,1,3-苯并噻二唑(SeBT)的共聚物(PFSeBT)的光伏电池，着重研究了阴极与共混比例对器件性能的影响，研究表明，当共混比例为PFSeBT: PCBM=1:2、并且采用LiF/Al做阴极时，器件的性能最优：开路电压1.00 V，为短路电流密度为4.42 mA/cm2，能量转换效率为1.67% (AM1.5，100 mW/cm2)，短路电流密度与入射光强间存在幂指数关系，幂指数为0.887，所有器件的光敏响应延均展至680 nm以上。上述研究结果表明，PFSeBT是一种非常有希望的聚合物光伏电池电子给体相材料。     

Study of Intense Electron Beams Produced by High-Voltage Pulsed Glow Discharges

We report the generation of high-current-density (20 A/cm2) pulsed electron beams from high-voltage (48-100 kV) glow discharges using cathodes 7.5 cm in diameter. The pulse duration was determined by the energy of the pulse generator and varied between 0.2 ?s and several microseconds, depending on the discharge current. The largest electron beam current (900 A) was obtained with an oxidized aluminum cathode in a helium-oxygen atmosphere. An oxidized magnesium cathode produced similar results, and a molybdenum cathode operated at considerably lower currents. A small-diameter (<1 mm) well-collimated beam of energetic electrons of very high current density (>1 kA/cm2) was also observed to develop in the center of the discharge. Electrostatic probe measurements show that the negative glow plasma density and the electron beam current have a similar spatial distribution. Electron temperatures of 1-1.5 eV were measured at 7 cm from the cathode. The plasma density (8.5 · 1011 cm-3 at 450 A) was found to depend linearly on the discharge current. In discharges at high currents a denser and higher temperature plasma region was observed to develop at approximately 20 cm from the cathode. We have modeled the process of electron beam generation and predicted the energy distribution of the electron beam. More than 95 percent of the electron beam energy is calculated to be within 10 percent of that corresponding to the discharge voltage.     

Generation and transport of high-current, low-energy electron beams in a system with a gas-filled diode

Investigations of the generation and transport of a high-current, low-energy electron beam are performed in a system with a gas-filled diode based on a plasma cathode. At accelerating voltages of up to 20 kV and pressures of (1–5)×10⁻¹ Pa, a beam with an emission current of 600 A, emission current density of 12 A/cm² and pulse duration of 30 μs if obtained in a diode with a grid-stabilized emission opening having a diameter equal to 8 cm. The beam is transported in the absence of an external magnetic field over a distance of 20 cm. The beam is compressed by its self-magnetic field, and the current density at the collector reaches 100 A/cm² when the beam diameter is 3 cm. Zh. Tekh. Fiz. 68, 44–48 (January 1998)     

Thermally stimulated current in polypropylene films charged in strong electric fields

We have observed a unique feature of the thermally stimulated depolarization (TSD) current in polypropylene (PP) films polarized in strong electric fields (up to 1–2 MV/cm). The direction of the TSD current is the same as the direction of the charging (polarizing) current, and the shape of the TSD current curve is much different from the standard curve. We show by computer model that these features can be explained by charge carrier injection in the film by charging from both electrodes. Both the charging curve shape and TSD current direction are explained by a model in which injected carriers form charged regions inside the film at a distance from the electrodes of one-fourth the thickness of the dielectric. Saint Petersburg State Technical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 12–20, April, 1997.     

Discharge in the Atmosphere in a Gaussian Beam of Subthreshold Millimeter Waves

The propagation velocities of a subthreshold discharge excited in air at atmospheric pressure by a pulsed microwave beam with a Gaussian field distribution, a wavelength of 4 mm, and an intensity up to 30 kW/cm² have been measured by means of optical and microwave diagnostics. It has been shown that the motion of a discharge front along the path of the beam toward the region of an increasing microwave field is accompanied by an increase in the velocity from subsonic (~10^–4 cm/s) to supersonic (~(6–8) × 10⁴ cm/s). At the same time, motion toward the decreasing field region is accompanied by a decrease in the velocity from supersonic to subsonic. It has been found that the maximum temperature of the gas in the discharge at velocities of ~10⁴ cm/s reaches ~5.3 kK.     

The nu(2), nu(4) + nu(5), nu(6) + nu(9), and nu(8) Band System in 1,1,1-Trifluoroethane

High-resolution FTIR spectra of 1,1,1-trifluoroethane (HFC-143a) have been recorded in the region from 1370 to 1470 cm(-1) with an unapodized resolution of 0.0016 cm(-1) at room temperature and of 0.004 cm(-1) at 183 and 100 K. The two main infrared active bands of A(1) symmetry have been shown to be nu(2) at 1407.5 cm(-1) and nu(4) + nu(5) at 1440.5 cm(-1). With the aid of Raman spectra, the two infrared inactive bands of E symmetry in this spectra region have been shown to be nu(8) at 1457.5 cm(-1) and nu(6) + nu(9) at 1446.2 cm(-1). The nu(2) band was analyzed as an isolated band, whereas the nu(4) + nu(5) band was analyzed as part of the triad nu(4) + nu(5), nu(6) + nu(9), and nu(8). Copyright 2000 Academic Press.     

Electronic excitation of the matrix during drift of excess electrons through solid xenon

It is shown experimentally that the exciton luminescence λ=172 nm) quantum yield excited by excess electrons drifting through solid xenon at 77 K in fields of 10 kV/cm amounts to 20±5 per electron and that luminescence takes place during the entire drift process. A CW bulky discharge through solid xenon (with a current up to 20 A/cm²) is realized, and intense visible luminescence due to excitation of impurities by electron impacts is observed. The prospects for using solid rare gases as matrices for studying processes in low-temperature plasmas and for creating effective electric energy converters in the vacuum ultraviolet range are discussed.     

Inert gas clusters ejected from bursting bubbles during sputtering

Ar(+)(n) cluster ions (n相似文献