New structure GaP—GaAlP heterojunction cold cathode

A negative electron affinity (NEA) GaP-GaAlP cold cathode with a new junction structure is proposed and demonstrated by improved fabrication techniques. Emission efficiencies as high as 0.7-1.1 percent were obtained from these cathodes. The energy distribution of the emitted electrons from the cold cathode had a full width at half-maximum of about 0.3 eV. A resolution of about 500 TV lines was obtained with a sealed off 1-in vidicon tube having the cold cathode and an Sb2S3target. The electron beam temperature was about 650 K. At present, highly stable and long life NEA cold cathodes can only be obtained by improving the activation method. It is proposed that the NEA p-GaP surface can be stabilized by a Cs, Sb, and O2activation.     

The influence of substrate temperature on the hydrogenated microcrystalline silicon growth through hollow cathode plasma

we exhibited the micro-hollow cathode (MHC) discharge to perform plasma enhanced chemical vapor deposition of hydrogenated microcrystalline silicon (μc-Si:H) in this paper. The role of substrate temperature on the μc-Si:H crystalline was focused. After testifying three substrates, glass, indium tin oxide (ITO) coating glass, and ITO coating polyimide (PI), we obtained over 80% crystalline volume fraction of μc-Si:H formed on the glass substrate. It was found that even the substrate temperature was as low as 120 °C the microcrystal Si can still be grown on ITO coating PI. We believe the high ionization rate in MHC due to hollow cathode effect promotes the microcrystal Si formation.     

Generation of High-Current-Density Sheet Electron Beams

High-current-density sheet beams directly generated from scandia-doped dispenser cathodes have been studied for application to vacuum electron devices like terahertz sources. Rectangular beams with current densities of over 50 $hbox{A/cm}^{2}$ have been developed and demonstrated to maintain for several hundred hours with the cathode operating stably at 950 $^{ circ}hbox{C}_{b}$. Beam forming structures have been investigated and optimized by means of beam profile simulation and confirmed by test results.      

Rb-H_2混合蒸气中5S_(1/2)→5P_(3/2)激光激发的速度选择布居与饱和效应

利用一步激发的饱和吸收光谱技术测量了激发态Rb(5P<,3/2)态的原子密度,室温下的Rb-H<,2混合蒸气被780nm激光激发,在激光线宽远小于Doppler线宽条件下,在激光功率40μW至5mw的范围内,测量了吸收系数,得到了5P<,3/2态的速度选择布居数密度.通过Rb空心阴极灯发出的5D→5P<,3/2窄谱线的吸收测量,也可以测得5P<,3/2态的原子密度,二种测量方法所得结果符合得很好.当氢气压为100Pa时,约8%基态原子被单模半导体激光器激发到5P<,3/2态.     

Electrical breakdown in vacuum

Theories and experimental facts of vacuum breakdown are reviewed. Measurements with gap spacings of 0.015 inch indicate little or no variation of breakdown with tube pressure between approximately 10^-5and 10^-7torr and with frequency of the applied voltage from 0 to 6 Mc/s. Variation of electrode materials, geometry, and surface preparations provide no marked improvements, but high voltage aging or conditioning does improve the breakdown characteristics by a factor of as much as 2 to 1. Enhanced field emission, from whisker-like protrusions on the cathode surface, causes individual beams of field-emission prebreakdown current to flow from cathode to anode. This prebreakdown current can cause resistive heating of the protrusion and localized electron-bombardment anode heating both of which produce vaporization and destructive effects which could lead to breakdown.     

Comparison of Cu-II 781 nm lasers using high-voltage hollow-cathodeand hollow-anode-cathode discharges

Voltage-current characteristics and the Cu-II 780.8 nm laser performances are described for a novel segmented hollow cathode and for three- and four-slot hollow-anode cathode (HAC) tubes. Each of these operate at a higher voltage and with higher slope resistance than a conventional hollow cathode and produce improved laser performance. The best laser performance is obtained with the segmented tube. The application of a longitudinal magnetic field raises the discharge voltage and enhances the laser performance for the segmented tube and raises the voltage for the four-slot HAC tube. The magnetic field lowers the voltage and reduces the laser performance with the three-slot HAC tube. The voltage effects are attributed to the deflection of the fast electrons by the magnetic field and represent experimental evidence for the oscillation of electrons in a hollow-cathode discharge     

Beam perturbations in confined flow electron beams with planar symmetry

An analysis of the perturbations in a confined flow beam from a two-anode gun as a result of lens effects at the gun apertures is presented for the case of parallel flow with planar symmetry. The results are presented in the form of plots of the amplitude of the perturbation as a function of the ratio of the final beam voltage at the second anode to the voltage of the first anode. The parameters are the magnetic field and the ratio of spacings between cathode and the first and second anodes. For magnetic fields greater than about twice the Brillouin field corresponding to the first anode voltage, the result is a very broad minimum of perturbation extending over a voltage ratio of the order of thirty to one up to a maximum voltage determined by the spacing ratio. The conditions for exact cancellation of the perturbation introduced at the first anode by the lens action of the second anode are considered, and a convenient chart for determination of these conditions is presented. The lens effect perturbation amplitude is shown to be much greater than that resulting from space charge in the absence of lens effects, except at or very near the voltage and spacing ratio that is correct for cancellation and at relatively low voltages and magnetic fields. It is also shown how these results can be applied to hollow cylindrical beams with and without center conductors.     

High performance low-temperature poly-Si n-channel TFTs for LCD

High-performance poly-Si TFTs were fabricated by a low-temperature 600°C process utilizing hard glass substrates. To achieve low threshold voltage (V_TH) and high field-effect mobility (μ_FE), the conditions for low-pressure chemical vapor deposition of the active layer poly-Si were optimized. Effective hydrogenation was studied using a multigate (maximum ten divisions) and thin-poly-Si-gate TFTs. The crystallinity of poly-Si after thermal annealing at 600°C depended strongly on the poly-Si deposition temperature and was maximum at 550-560°C. The V_TH and μ_FE showed a minimum and a maximum, respectively, at that poly-Si deposition temperature. The TFTs with poly-Si deposited at 500°C and a 1000-Å gate had a V _TH of 6.2 V and μ_FE of 37 cm²/V-s. The high-speed operation of an enhancement-enhancement type ring oscillator showed its applicability to logic circuits. The TFTs were successfully applied to 3.3-in.-diagonal LCDs with integration of scan and data drive circuits     

激光激发的铀原子荧光光谱

以直流空心阴极灯作蒸气源,以若丹明6G染料激光作激发光源,简单方便地观测到铀原子的753.393、763.175和763.954nm荧光辐射。对消除以灯辐射为主的强背景作了详细讨论。     

The Numerical Simulation Study of Pseudospark Hollow Cathode Discharge

Pseudospark discharges are sources of intense electron beams. Reported in this paper are theoretical studies of the Pseudospark discharges. A theoretical and computational model has been adopted to study the initiation phase of Pseudospark discharges via a two-dimensional electrostatic particle-in-cell plus Monte Carlo (PIC-MCC) collision method. From the numerical results, a sequence of physical events has been identified. It has been found that the ionization processes determined by local electric field and hollow cathode effect. The growth phenomena is dependent of α ionization multiplication due to local space charge from initial ionization growth to onset of the hollow cathode effect, and then hollow cathode effect become leading factor.     

Vacuum arc ion currents and electrode phenomena

Properties of dc vacuum arcs between copper electrodes are studied in both a vacuum interrupter and a metal walled arc chamber. Maximum ion currents of ∼8 to 20 percent of the arc current (100 to 3000 A) are drawn from the diffuse arc plasma when the bounding metal wall or shield is biased negative. This maximum ion current is a fundamental arc property independent of wall diameter, anode diameter, and electrode spacing. The geometric dependence of the wall ion current, together with observations of isotropic vapor and ion emission from the cathode, indicates that the cathode regions adjacent to the cathode spots are the predominant sources of ionization for the plasma. Assuming single ionization, 55 percent of the vapor leaving these regions is ionized. Starvation phenomena in the anode region remote from the cathode spots lead to anode voltage drop and anode spot formation. Post arc currents reveal a mean ion speed during arcing of ≈8×10⁵cm/s. This mean speed may be acquired in the cathode region by acceleration from a potential maximum.     

A new DC plasma display panel using microbridge structure andhollow cathode discharge

A newly designed dc plasma display panel (PDP) using a microbridge structure and hollow cathode has been proposed, and its characteristics have been measured. This new plasma display panel operates in an abnormal glow in the current range from 0-50 μA at 500 torr, with an effective internal resistance of 800 KΩ. This means that the internal resistance is high enough that a resistor-in-cell structure is not necessary any more for the dc PDP. The luminous efficiency of the hollow cathode discharge is at least five times as great as that of subnormal and normal glow discharges. The lifetime of the display panel is shown to be quite insensitive to gas pressure in the range of 400-1100 torr because the sputtered materials are trapped inside the hollow cathode     

Study of electron emitters for use in gas lasers

This paper describes various types of electron emitters that have been tested under conditions of interest in gas laser operations. In general, where "nonreactive" gases are used, some form of the BaSrO cathode will meet many requirements. Several matrix structures containing BaSrO are described that will stand up better under adverse conditions (ion bombardment, envelope poisoning) than the conventional sprayed cathode. Several hot hollow cathodes for use at high (15-100 amperes) currents were studied and are discussed. With reactive gases, such as O2, CO2, H2O, a BaZrO3cathode has been found to be very useful. This cathode is unique in that it emits better in an oxidizing atmosphere than it does in either an inert gas or vacuum.     

The design and performance of a magnetron-injection gun

The space-charge flow solutions described by Kino and others in connection with the crossed-field carcinotron gun can be generalized to form the basis of a magnetron-injection gun design suitable for the production of hollow electron beams. In the first part of the paper this generalization is described. From the resulting flow it is possible to determine by an approximate method the electrodes to produce a gun of desired perveance with nearly uniform current density at the cathode. This technique has been used to design guns having ratios of cathode length to a diameter considerably greater than unity. The close agreement between the results obtained on several experimental guns and the theoretical predictions is described, along with the effect of departures from the prescribed fields given by the design method.     

Proposal of field-emission device surrounded by high-k dielectric and performance prospects

We propose a field-emission device surrounded by high-k dielectric (FESH) that used a Spindt-type emitter; its design guidelines are demonstrated using various device parameters. The most significant aspect of the FESH structure is its use of high-k dielectric material to surround the emitter. The large dielectric constant of the high-k dielectric dramatically reduces the threshold voltage when applying dc voltage. It is shown that the most suitable device parameters can be extracted from the viewpoint of figure-of-merit. When dc voltage is applied to a FESH device, a large transient current flows between the anode and the cathode. The application of an ac voltage eliminates the current leakage that would otherwise hinder the development of practical applications such as displays. It is demonstrated from dynamic simulations that sinusoidal input pulses should be applied to FESH devices rather than rectangular input pulses since the former realizes the benefits of low-power operation and high reliability.     

碳纳米管场发射显示器特性测试方法的研讨

通过低压化学气相沉积法在硅片上制作碳纳米管薄膜阴极,用真空荧光显示器的封装工艺,制备了碳纳米管场发射显示器样管。改变常用的驱动电源电压测试为器件电压测试,得到非常理想的伏安特性曲线和发光特性曲线。从测试结果分析可知,直接测量碳纳米管场发射显示器的器件电压和测试电源驱动电压所得结果是不同的,用后者代替前者不够合理。从电子场发射的角度看,实际的碳纳米管场发射伏安特性曲线应比测试的伏安曲线更陡。     

阴极门控光学条纹相机

为满足惯性约束聚变（ICF）物理实验诊断中对高信噪比低噪声光学条纹相机的需求,基于六电极同轴型扫描变像管发展了一种阴极门控光学条纹相机。该相机通过阴极预置直流高压叠加门控脉冲电压的方法,使相机变像管电压只有在门控脉冲加载时间内处于正常工作状态,才能对阴极发射的电子进行正常聚焦扫描,而在非加载门控脉冲时间内,变像管的第二聚焦电极处电压低于阴极电压,从而使阴极发射的光电子被反向截止,因此相机只对在门控脉冲加载时间内到达的有用信号进行测量,从而有效抑制了光学条纹相机受环境光辐照而引入的背景噪声,提升了相机的信噪比。验证实验表明,通过在阴极上加载幅度?5.5 kV、脉宽203 ns的门控脉冲电压,即可较大程度降低相机噪声,同时可维持相机的空间分辨率。     

Performance, uniformity, and yield of 850-nm VCSELs deposited by MOVPE

Vertical-cavity surface-emitting lasers (VCSELs) emitting near 850 nm and fabricated with the metal-organic vapor phase epitaxy (MOVPE) epitaxial growth technique and a planar proton implant process have been demonstrated with excellent performance, uniformity, and yield across a 3-in wafer. Four thousand lasers were tested on a three-inch-diameter wafer, with a yield of 99.8%. This translates into a yield of 94% for fully functional 34/spl times/1 arrays. The average threshold current, threshold voltage, and dynamic resistance at 10 mA operating current were 3.07 mA, 1.59 V, and 34 ohms, respectively. Uniformity of better than /spl plusmn/9% in threshold current, /spl plusmn/1% in threshold voltage, and /spl plusmn/1.5% in maximum optical output power across a 34-element array was demonstrated.     

Life test studies on tungsten impregnated cathodes

NASA-Lewis Research Center has conducted an ongoing life test program on commercial impregnated tungsten cathodes since 1971. This brief is an update of the information as of December 1979. "B"-type cathodes, operated at 1100°C have been run in simulated microwave tubes at 2 A/cm²for more than four years with about 6- percent degradation in current at a constant reference anode voltage. "M'-type cathodes have been operated for 30 000 h at a cathode temperature of 1010°C and 2 A/cm²with no degradation in current at a constant reference anode voltage.     

AC Microplasma Device With a Cylindrical Hollow Electrode for Improving Luminous Efficacy

In this paper, a device utilizing the hollow cathode discharge is demonstrated to diagnose the possibility of improving luminous efficacy of a microplasma device. A series of experiments is conducted by measuring luminous efficacy, which is an important factor in display devices, in accordance with specifications of the cylindrical hollow and gas pressure. The proposed structure has two electrodes, and one of them contained a cylindrical hole and is called a hollow electrode. The hollow electrode works as either a cathode or an anode alternately due to the ac operating conditions. When the hollow electrode operated as a cathode, the luminous efficacy is higher than that of the anode case, and this tendency is observed consistently throughout all experiments. Moreover, from the measurement results on the tendency of luminous efficacy in terms of hole specifications, different aspects of luminous efficacy are obtained, depending on whether the variation is in the diameter or in the depth. In case of the diameter, the luminous efficacy is improved when $p cdot D$ (i.e., the product of the gas pressure and the diameter of the cylindrical hole) is less than one $hbox{Torr} cdot hbox{cm}$. In the case of the depth, the maximum value of luminous efficacy exists at the certain $p cdot d$ (i.e., the product of the gas pressure and the depth of the cylindrical hole).