Grain boundary effect on the electrical properties of boron-doped polysilicon films

The effect of grain boundary width has been accounted for and a modified simple model of average carrier concentration is presented considering the transport mechanism of charge carriers by thermionic emission only. It is found that the electrical properties of polysilicon are very sensitive to doping concentration when the grain size is small and the effect of grain boundary width on electrical properties increases as the grain size decreases. The inclusion of grain boundary width in resistivity and mobility formulae also gives better results near the critical doping concentration. The proposed model gives better agreement between experimental data and theoretical results.     

Temperature dependence of current—voltage characteristics of Au/n-GaAs epitaxial Schottky diode

The influence of temperature on current-voltage (I-V) characteristics of Au/n-GaAs Schottky diode formed on n-GaAs epitaxial layer grown by metal organic chemical vapour deposition technique has been investigated. The dopant concentration in the epitaxial layer is 1 X 10¹⁶ cm^-3. The change in various parameters of the diode like Schottky barrier height (SBH), ideality factor and reverse breakdown voltage as a function of temperature in the range 80–300 K is presented. The variation of apparent Schottky barrier height and ideality factor with temperature has been explained considering lateral inhomogeneities in the Schottky barrier height in nanometer scale lengths at the metal-semiconductor interface     

Function of Oxygen in Mo-La2O3 Cathode

Different atomic ratio La/O film cathodes were prepared by pulsed laser deposition under various vacuum conditions. The emission properties were measured and their surface composition was investigated with in situ AES analyses. The function of oxygen in thermoionic emission of Mo-La2O3 cathode was investigated. Excess oxygen is negative to electron emission because lanthanum is easy to become stable La2O3, but proper proportion oxygen can weaken the evaporation of lanthanum and conduce to cathodes＇ stable work. The formation of oxygen vacancies enhances semiconductor property of La-O compound and improves greatly the performance of cathodes.     

Mass-Spectrometric Study of the Kinetics of Ionic and Molecular Sublimation of Sodium Chloride Single Crystals

A mass-spectrometric method is used to study the kinetics of ionic and molecular sublimation of sodium chloride single crystals. The positive ions Na⁺, Na₂ ⁺, and Na₂Cl⁺ were identified in the mass spectrum in the temperature range 820–970 K. Up to 970 K no emission of negative ions was observed. The temperature dependence of thermal ion currents, lnI _i – (1/T), exhibits a maximum and a minimum successively with increasing temperature. These features are identified with a change in the electrical properties of the surface. It is inferred that in the intrinsic temperature range the sign of the surface charge in NaCl is negative and thus the Gibbs free energy of formation of cation vacancies is greater than that of anion vacancies. In the electron impact ionization mass spectrum of molecular fluxes vaporized from an open crystal surface, Na⁺, NaCl⁺, and Na₂Cl⁺ ions originating from NaCl and Na₂Cl₂ precursors are detected in the temperature range 779–982 K. The dimer-to-monomer ratio is found to be of the same order of magnitude in the cases of equilibrium and free-surface vaporization. However, the dependence on temperature of this ratio is different in these two cases. Mechanisms which account for this observation are discussed in light of the terrace–ledge–kink and surface charge models.     

一种微波栅控直流电子枪初步物理设计

红外波段自由电子激光的小信号增益大小以及饱和功率对束流的能散非常敏感。为满足远红外自由电子激光对能散的要求,在合肥光源栅控直流高压电子枪的基础上,模拟了一种热阴极微波栅控直流高压电子枪。微波栅控直流高压电子枪采用微波栅控的方法,控制和压缩阴极引出电子束团的长度。再通过直流高压对电子加速后,在电子枪的出口可以得到量级为几十皮秒的束团。本文使用SUPERFISH、POISSON分别进行栅控微波场与高压电场优化计算,PARMELA(Phase And Radial Motion in Electron Linear Accelerators)进行束流跟踪与分析,得到一组能满足红外自由电子激光需求的电子枪参数。     

含稀土氧化物难熔盐浸渍W基直热式阴极研究

为了提高磁控管阴极的工作性能, 采用新型La₂O₃/Y₂O₃-Gd₂O₃-ZrO₂难熔盐浸渍W基制备直热式阴极, 并对该阴极的热发射特性和寿命特性等进行了测试。热发射测试结果表明, La₂O₃-Gd₂O₃-ZrO₂浸渍阴极在1600℃可提供超过0.18 A/cm²的空间电荷限制区电流密度。在同等发射电流下, 该浸渍阴极的工作温度比纯W阴极降低至少300℃, 该阴极在1750℃, 0.5 A/cm²直流负载下, 可以连续工作2100 h。当以Y₂O₃代替La₂O₃, 采用相同的配比制备阴极时, 1400℃、1700℃下即可分别提供超过0.6、3.4 A/cm²的空间电荷限制区电流密度。Y₂O₃-Gd₂O₃-ZrO₂浸渍阴极的工作温度比La₂O₃-Gd₂O₃-ZrO₂浸渍阴极降低至少400℃, 该阴极在1600℃, 1.5 A/cm²直流负载下, 可以连续工作2600 h。最后, 对这两种新型含稀土氧化物难熔盐浸渍阴极的热发射机理进行了探讨。     

La2O3-Mo热发射材料的研究

采用溶胶凝胶(Sol-Gel)和两步氢还原及烧结法成功制备了(2%～5%),质量分数,下同)La2O3-Mo阴极粉末和烧结体,借助于XRD,SEM等手段对材料成分及微观结构进行分析.结果显示在粉末和烧结体中稀土元素La以氧化物形式存在,La2O3粒子大小为100nm,弥散分布在烧结体基体中.热发射测试结果表明1400℃时,零场发射电流达到J0=6A/cm^2.暴露大气48h后,再经过1350℃激活,发射性能得到全面恢复.     

Heating graphene to incandescence and the measurement of its work function by the thermionic emission method

The work function （WF） of graphene is an essential parameter in graphene electronics. We have derived the WF of graphene by the thermionic emission method. Chemical vapor deposition （CVD）-grown single-layered polycrystalline graphene on copper foil is transferred to a cross-stacked carbon nanotube （CNT） film drawn from a super-aligned multiwalled CNT array. By decreasing the pore size of the CNT film, the as-prepared CNT-graphene film （CGF） can be Joule heated to a temperature as high as 1,800 K in vacuum without obvious destruction in the graphene structure. By studying the thermionic emission, we derive the WF of graphene, ranging from 4.7 to 4.8 eV with the average value being 4.74 eV. Because the substrate influence can be minimized by virtue of the porous nature of the CNT film and the influence of adsorbents can be excluded due to the high temperature during the thermionic emission, the measured WF of graphene can be regarded as intrinsic.     

FCS在热媒炉控制中的应用

简单阐明热媒炉系统工艺情况，介绍现场总线控制系统软、硬件配置，着重分析现场总线控制系统控制策略组态。     

Thermionic properties of Mo-La_2O_3 cathode wires

The recent advances in Mo-La2O3 thermionic cathode materials were presented. It is shown that Mo-La2O3 cathode has better ductility, radioactive pollution-free, excellent thermionic electron-emission properties and lower operating temperature compared with W-ThO2 cathode. At operating temperature 1350～1400℃, the average saturation current of the Mo-La2O3 cathode is 118mA, the corresponding average current density is 367mA/cm2, and the average emission efficiency is 11.8mA/W. The lifetime of diode is more than 2000h when the stable emission current is 80mA. Moreover, the lifetime of practical 6T51-type triode is more than 1000h. These advances show that the Mo-La2O3 cathode electron tube is closer to industry application.