氧化钪掺杂钨基扩散阴极的结构、表面与发射特性的研究

以钪盐的水溶液与氧化钨液-固掺杂法制备了氧化钪掺杂钨基扩散阴极，利用扫描电镜、能谱分析仪和原位俄歇电子谱仪等现代分析技术研究了烧结体的形貌、Sc的分布及阴极的表面特性。用自行研制的微机控制全自动电子发射测量装置检测了阴极发射性能。研究表明，与Sc2O3与W机械混合制备的混合基含Sc阴极相比，采用液固掺杂法制备的阴极，Sc2O3分布均匀，阴极耐高温和抗离子轰击能力强，发射性能优异。     

电致伸缩与PLZT电子发射频率特性的关系

研究了PLZT阴极中电致伸缩效应对电子发射频率的影响.采用等静压工艺制备了PLZT阴极样品,并在阴极上施加高达11 kV的激励脉冲,观察到电子发射波形周期性地出现多个峰值.对收集到的电子发射波形进行频谱分析,得到主要频率成分在5.8 MHz左右,与根据压电声表面波理论计算出的表面振动基频为6.2 MHz接近.基于以上实验结果和计算结果,结合目前铁电电子发射的快极化反转和表面等离子体理论,可得出压电表面振动对电子发射波形进行了频率调制,合理解释了电子发射波形周期性出现多个峰值的现象.     

阴极蒸发物电子发射现象的研究

为研究钡钨阴极蒸发物的电子发射现象,采用一种新设计的测试装置,对沉积在多晶钨表面上阴极蒸发物的电子发射曲线进行了采集,利用电子发射显微镜和扫描电镜对蒸发物沉积层的电子发射像、表面形貌和成分进行了分析。结果表明,电子发射曲线分3段,即陡升段、快升段和缓升段。分析认为,发射曲线的3段依次对应着多晶钨表面的晶界及划痕发射、晶面发射和3维岛状发射。实践证明,在覆膜阴极表面构造均匀弥散分布的岛状晶体发射点,可大幅度提高阴极的电子发射性能。     

一种贮存式氧化物阴极

该文论述了一种新的贮存式氧化物阴极。这种阴极的直流发射、脉冲发射和阴极寿命性能都比普通氧化物阴极好。文中对阴极发射材料的形貌、贮存活性物质的结构进行了分析,观察了阴极镍网表面电子发射图像,讨论了阴极发射机理。     

提高PZT阴极电子发射性能的实验研究

实验研究了提高PZT(锆钛酸铅)阴极电子发射性能.在电子发射快极化反转机理的基础上,分析了电流发射密度随激励场强增大的原因.通过电极绝缘保护层改散了阴极的表面击穿特性,通过等静压工艺改善了阴极的体击穿特性和通过Mn2+的添加提高材料本生的耐电压强度,从而提高了施加在阴极上的激励场强值.实验数据显示等静压工艺、高的激励场强、绝缘保护层、Mn2+的添加等均有利于阴极的电流发射,发射电流密度提高到123 A/cm2.     

复铼膜阴极的发射和表面特性

本文报道了复铼膜扩散阴极的发射和表面特性的研究结果,并与S-型阴极进行了比较。实验结果表明:S-型阴极复铼膜后,其热电子发射明显提高,且分布均匀。月极表面上主要元素的俄歇像显示Ba在复铼膜阴极表面上的分布要比在S-型阴极表面上均匀得多,Ba的低能Auger谱和XPS的研究表明:与S-型阴极相比Ba在复铼膜阴极表面上呈现更强的金属特性。这可能是S-型阴极复铼膜后发射增大的主要原因。     

等离子喷涂氧化物阴极的涂层表面分析探讨

本文对等离子喷涂氧化物阴极的涂层表面电子发射均匀性、逸出功、激活前后成分进行了分析,并探讨了阴极表面成分变化的原因。实验结果显示,等离子喷涂氧化物阴极电子发射密度大而且均匀,逸出功分布在1.52~1.58eV之间占到80%,跟激活前的阴极相比,激活后的阴极表面成分除了作为参考的Ca,其他元素都有不同程度的降低,包括表面活性物质Ba。本文最后探讨了阴极表面Ba元素减少的原因。     

有害气体对氧化物阴极发射的影响

介绍了各种气体对氧化物阴极发射的影响。特别是与空气污染有紧密关系的SO_2、NO_2、和Cl_2。为了比较,也试验了Na、CO_2、H_2O、O_2、CO、H_2和Ar等大气的主要成分的毒害效应。详细的研究各种气体对氧化物阴极和氧化物材料发射的影响。沾污了的阴极的中毒状态用二次电子显微镜和俄歇谱仪进行了分析。还研究了阴极激活之前,有害气体对碳酸盐发射的影响。     

表面势垒形状对NEA光阴极电子能量分布的影响

通过计算电子到达阴极面时的能量分布和求解电子隧穿表面势垒的薛定谔方程得到了透射式NEA GaAs光阴极发射电子能量分布的计算公式.利用该公式仿真研究了阴极表面势垒形状对电子能量分布的影响,发现I势垒变化对阴极的量子效率影响显著,其中尤以I势垒宽度影响更大,而Ⅱ势垒则影响阴极的能量展宽,其中真空能级的升高可使阴极电子能量分布更集中,但却牺牲了一定的阴极量子效率.拟合分析了实验测试的透射式阴极电子能量分布曲线,实验与理论曲线吻合得很好,并得到了阴极的表面势垒参数.     

表面势垒形状对NEA光阴极电子能量分布的影响

通过计算电子到达阴极面时的能量分布和求解电子隧穿表面势垒的薛定谔方程得到了透射式NEA GaAs光阴极发射电子能量分布的计算公式.利用该公式仿真研究了阴极表面势垒形状对电子能量分布的影响,发现I势垒变化对阴极的量子效率影响显著,其中尤以I势垒宽度影响更大,而Ⅱ势垒则影响阴极的能量展宽,其中真空能级的升高可使阴极电子能量分布更集中,但却牺牲了一定的阴极量子效率.拟合分析了实验测试的透射式阴极电子能量分布曲线,实验与理论曲线吻合得很好,并得到了阴极的表面势垒参数.     

紫外铜离子激光器的理论研究

系统研究了连续工作的紫外铜离子激光器理论,即空心阴极放电的阴极位降理论,阴极溅射,放电等离子体中粒子的扩散和粒子数密度的速率方程。计算结果由实验得到验证。     

Fiber-compatible K+-Na+ ion-exchanged channelwaveguides: fabrication and characterization

A systematic study of waveguides fabricated by K⁺-Na ⁺ exchange in soda-lime silicate and BK7 glasses is presented. The measured K⁺ concentration profile, the refractive index profile, and the diffusion profile obtained by solving the one-dimensional diffusion equation are correlated to explain the differences in the index profiles in the two glasses. The mobility of the potassium ions was measured by fabricating waveguides using electromigration. Surface waveguides formed by diffusion from a molten KNO₃ salt bath were buried by applying an electric field. Single-mode channel waveguides for operation at a wavelength of 1.3 μm that exhibit excellent mode matching with conventional optical fibers, achieving a fiber-waveguide insertion loss of less than 1 dB for a 20-mm-long waveguide, have been obtained     

Enhanced power performance of enhancement-mode Al0.5Ga0.5As/In0.15Ga0.85As pHEMTs using alow-k BCB passivation

Surface passivation technology plays an important role, especially in E-mode pHEMTs applications, and a new passivation technology has been proposed in this study. This novel benzocyclobutene (BCB) passivation layer takes advantage of the low dielectric permittivity (2.7) and a low loss tangent (0.0008). In this letter, we not only suppress the gate-to-drain leakage current but also improve the device power performance under a high input power swing by using a BCB passivation layer. The passivated 1.0 μm-long gate pHEMTs exhibit a better off-state performance than the unpassivated ones. The maximum output power under a 2.4-GHz operation is 118 mW/mm, with a linear power gain of 11.1 dB and a power-added efficiency is 60%     

Very-shallow low-resistivity p+-n junctions for CMOS technology

Shallow p-n junctions 110 nm deep have been fabricated using rapid thermal diffusion from a spin-on oxide source. Surface concentrations greater than 3 × 10²⁰cm^-3are possible, with sheet resistivities less than 100 Ω/sq and a maximum reverse-bias leakage at 5 V of 3 nA.cm^-2. Results from 150-nm junctions are also given and are compared with BF2ion implantation.     

磁控管用新型直热式稀土铪酸钆陶瓷阴极研究

为了提高大功率磁控管的输出功率,延长其使用寿命,采用难熔稀土氧化钆和过渡金属氧化铪制备大功率磁控管用新型直热式稀土铪酸钆陶瓷阴极,并对该阴极的热发射特性和寿命特性等进行了测试,热发射测试结果显示该阴极在1300℃ br即可提供0.1A/cm²发射电流密度,1600℃ br下可提供超过1.93A/cm²的发射电流密度.寿命实验结果显示,该阴极在1500℃ br,直流负载为0.5A/cm²的条件下,寿命已经超过4000h.最后,利用X射线衍射仪、扫描电镜、能谱分析仪、氩离子深度刻蚀俄歇电镜等设备分别对该阴极活性物质的分子结构,阴极表面微观形貌、元素成分及含量等进行了分析.结果表明,高温烧结合成了单一的铪酸钆物相,烧结过程中当一种Gd³⁺价稀土氧化钆掺入Hf⁴⁺价的过渡金属氧化铪时,会发生离子置换固溶,为了保持铪酸钆晶格的电中性,晶格中就会产生一个氧空位.当阴极在激活、老练、热发射测试时,会加速氧空位的生成,产生的氧空位越多,阴极表面导电性就会越好,这间接降低了逸出功,从而提高了阴极的热发射能力.     

Formation of planar n+pockets in GaAs for mixer diode fabrication

A novel technique has been developed to produce n⁺"pockets" in semi-insulating GaAs bulk material. This technique has produced thick pockets of highly conducting epitaxial material on the substrate surface. The pockets were formed by the growth of a liquid-phase epitaxial (LPE) layer into holes which had been etched into the substrate. Surface uniformity was obtained by chemo-mechanically polishing the substrate surface under tightly controlled conditions. Polishing rates as low as 0.2 µm/min have been obtained. Photographs taken of the pocket cross-sectional area have revealed that growth occurred throughout the entire pocket region. Growth was even found to have occurred along the irregularly shape walls of the pockets. The continuous growth throughout the pockets coupled with the subsequent polishing of the substrate have produced exceptionally smooth and planar surfaces. Thicknesses as great as 10 µm have been obtained for the n⁺pockets using this technique. Mixer diodes have been fabricated onto these layers and tested. Preliminary dc measurements taken on these devices have yielded a zero-biased cutoff frequency (Fco) of 800 GHz with a series resistance (Rs) of 6 Ω and a zero-biased capacitance (C0) of 30 fF.     

Surface properties of AlInGaN/GaN heterostructure

Surface structural, electronic and electrical properties of the quaternary alloy AlInGaN/GaN heterostructures are investigated. Surface termination, atomic arrangement, electronic and electrical properties of the (0001) surface and (10–11) V-defect facets have been experimentally analyzed using various surface sensitive techniques including spectroscopy and microscopy. Moreover, the effect of sub-band gap (of the barrier layer) illumination on contact potential difference (V_CPD) and the role of oxygen chemisorption have been studied.     

Large enhancement of interband tunneling current densities of over105 A/cm2 inIn0.53Ga0.47As-based surface tunnel transistors

In_0.53Ga_0.47As-based Surface Tunnel Transistors (STT's), which control an interband tunneling current between an n-type channel and a p-type drain by an insulated gate, are investigated with the goal of increasing the tunneling current-density for high-speed operation. The fabricated devices enhanced an interband tunneling current density by a factor of 10² compared to the conventional GaAs-STT's due to a smaller bandgap energy and a lighter electron effective mass, and exhibited a clear gate-controlled negative differential resistance (NDR) characteristics with maximum tunneling current densities of over 10⁵ A/cm². The cutoff frequency (F_T) and maximum oscillation frequency (f_max ) of a fabricated device with a 1.0-μm gate length were estimated to be 7.9 GHz and 20 GHz, respectively, in the NDR region     

In0.52Al0.48As/In0.53Ga0.47As/In0.52Al0.48As abrupt double-heterojunction bipolar transistors

In0.52Al0.48As/In0.53Ga0.47As/In0.52Al0.48As n-p-n abrupt double-heterojunction bipolar transistors grown by molecular beam epitaxy (MBE) have been realized for the first time. DC current gains in excess of 300 have been measured on devices operated in the emitter-up configuration. DC current gains around 50 are obtained on device structures with Be+ implanted extrinsic base regions operated in the emitter-down configuration. The carrier injection and collection behavior of the abrupt InGaAs/InAlAs heterojunctions is discussed.     

Effects of surface pretreatment of polysilicon electrode prior toSi3N4 deposition on the electrical characteristicsof Si3N4 dielectric films

Effects of various surface pretreatments of polysilicon electrode prior to Si₃N₄ deposition on leakage current, time-dependent dielectric breakdown (TDDB) and charge trapping characteristics of thin Si₃N₄ films deposited on rugged and smooth poly-Si are investigated. Surface pretreatments consist of different combinations of HF clean, rapid thermal H₂ -Ar clean, and rapid thermal NH₃-nitridation (RTN) and are intended to modify the surface of bottom poly-Si electrode. Results show that RTN treatments lead to lower leakage current, reduced charge trapping, and superior TDDB characteristics as compared to rapid thermal H₂-Ar clean