Sputtering the surface of a He-Ne laser cathode

The results from analyzing the surface of an aluminum cathode by means of atomic force microscopy (AFM) and Auger electron spectroscopy (AES) are presented. Cathode surface sputtering is simulated via the Monte Carlo method using the SRIM program. Factors affecting the formation of the surface relief of cold cathodes under the action of bombarding ions are discussed along with the main mechanisms of surface modification and ways of enhancing the stability of the material with respect to the action of ions.     

Electron conduction associated with the chemical transport of reducing elements in oxide cathode for CRT's application

In the present work, the formation of compounds associated to the diffusion of reducing elements (Mg, Al and W) to the Ni cap surface of oxide cathode has been studied by a new method. This method used two cathodes, one of them is coated and the other is uncoated, to be in an attach-contact mounted in a dummy tube. Different analytical techniques were used for this study: scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX) and I/V electrical measurements. After oxide cathode plus decomposited and activated, Al and Mg doping elements take place during heating to 810 °C (Ni-Br) under a rich controlled Ba/SrO atmosphere through an acceleration life test.It is shown that the chemical transport occurs mainly by a grain boundary mechanism with significant pile-up of Mg compounds. Al and W show a superficial concentrations and distribution.The dc electrical characteristic shows very strong rectifying behaviour through the M-S junction due to the I/V curves, particularly after 144 h acceleration life time. The characteristics are found to be reversible and reproducible, and viewed a rectification ratio (r) of 100. The calculated ideality factor shows a value of n = 9.6, which is evidenced to the tunnelling conduction.The theoretical calculation shows that the interface thickness grows to (∼6 μm) after accelerated the cathode to 1896 h.     

Changes in surface chemistry of an Ir---W mixed metal coated cathode during activation

A comparative study has been made between a mixed metal (60% Ir-40%W) coated cathode and a “B” cathode during activation and also in their respective steady states. The rate limiting factor in the activation of the coated cathode is the oxidation of the initial Ba type surface to a BaO type surface. Since on the “B” cathode Ba and O emerge together, its activation is faster than the coated cathode. In the steady state of operation, both cathodes exhibit a surface near BaO stoichiometry which is the optimum composition for the minimum work function. This work function is about 0.2 eV lower on the coated cathode than on the “B” cathode. An accelerated life test at 1575 K indicated a gradual decrease of the Ir concentration in the coating.     

Study on electron emission suppression characteristic of molybdenum grid coated with Hf film by ion beam assisted deposition

Hf was deposited onto the surface of molybdenum grids by ion beam assisted deposition (IBAD). The electron emission characteristics from molybdenum grids with and without Hf, which were contaminated by active electron emission substances (Ba, BaO) of the cathode, were measured using an analogous diode method. The results show that electron emission from the grid coated with Hf film was less than that from molybdenum grid without Hf. The mechanism for electron emission suppression of the grids coated with Hf film was discussed.     

Fabrication and analysis of buried iron silicide microstructures using a focused low energy electron beam

We fabricated iron and iron silicide microstructures on an Si(1 0 0) clean surface via electron beam induced process of Fe(CO)₅ multilayer and subsequent annealing. The fabricated microstructures were in situ analyzed by Auger electron spectroscopy (AES) and scanning electron microscopy (SEM). We successfully analyzed the coverage and chemical states of the artificial deposited iron structure area-selectively by AES. The artificial iron structure was fabricated after heating to above 350 K to desorb residual Fe(CO)₅ species. The artificial structure was observed even after 1190 K annealing by SEM, but AES measurements showed it to be covered by Si atoms. We concluded that the buried iron silicide microstructure was formed by the present process.     

表面形貌对热阴极电子发射特性的影响

为了研究热阴极表面形貌对电子发射能力的影响,使用飞秒激光微纳加工技术在光滑的热阴极表面制备不同尺寸和形状的周期性条纹结构,并使用相同的制备工艺对阴极进行除气和激活.测试结果显示:阴极表面周期性条纹结构可有效增强阴极的电子发射能力,正交双向条纹结构表面阴极的发射电流密度高于单向条纹结构表面阴极的发射电流密度,而且随条纹结构尺寸的降低,阴极的电子发射能力逐渐增强.对阴极表面形貌进行仿真,发现微尖顶端位置在强电场的作用下具有较强的电子发射能力.当阴极表面微尖底部直径与高度比值(r/h)较小时,微尖的侧面仍是阴极电子发射的主要区域,但是随着r/h减小,阴极的电子发射区域逐渐由微尖侧面发射向微尖顶端转移,场助电子发射效应成为阴极电子发射的主要组成部分.     

Sc2O3-W matrix impregnated cathode with spherical grains

Sc₂O₃-W matrix cathodes have been prepared by using a liquid-liquid doping method combined with high-temperature sintering. The microstructure and physical behavior of active substances of scandia-doped tungsten matrix and impregnated cathode has been studied by SEM and AES methods. The results show that the matrix has a homogeneous structure composed of W grains with spherical shape and superfine Sc₂O₃ particles dispersed uniformly over and among W grains. After impregnation, this Sc-type impregnated cathode has high emission capability. Space-charge-limited current density could reach 52 A/cm² at 850 °C_b. The high emission results from a Ba-Sc-O active layer with a thickness of about 80 nm, which is formed at the cathode surface during the activation period. Both the decrease of the thickness of active surface layer and the decrease of the content of Sc at the surface could lead to the degradation of current density during operation.     

SURFACE PLASMON OF Ag CLUSTERS ON ALUMINA FILMS

The deposition of silver on an ordered alumina film prepared on Re(0001) surface has been studied by Auger electron spectroscopy (AES), low energy electron diffraction (LEED) and high resolution electron energy loss spectroscopy (HREELS). The results show that Ag grows initially as clusters at 90K and 300K. A red shift of the Ag surface plasmon as a function of decreasing coverage is observed, which is related to the cluster size effect. A surface plasmon characteristic of metallic Ag appears at coverages higher than 2.8 monolayer equivalent.     

Diffusion and desorption of barium and oxygen on tungsten dispenser cathode surfaces

Auger measurements have been made on the concentration of barium and oxygen diffusing out of a pore and slot onto the surface of a simulated tungsten dispenser cathode. Profiles of concentration vs distance from the source were obtained at different temperatures. It is found that at cathode operating temperatures very little gradient of oxygen concentration exists on the surface, and under steady state conditions Ba is the main diffusing species. Ba diffusion distances derived are consistent with previous measurements. However it is found that this distance increases with concentration in spite of the fact that the Ba surface lifetime decreases with concentration. Time dependent measurements made on a clean surface show that the rate of Ba and O build up is limited by the supply rate of oxygen to the surface. This supply rate is not diffusion limited but seems to be limited by the mechanism generating free oxygen. A comparison of emission microscope measurements on a tungsten matrix dispenser cathode with the simulated cathode data indicates that similar oxygen generation processes may be controlling the activation of these cathodes.     

原电池法室温制备Ba_(1-x)Ca_xMoO_4固溶体薄膜

在含Ca_~(2+)和Ba~(2+)的碱性溶液中,通过原电池法在室温条件下制备了Ba_(1-x)Ca_xMoO_4多晶固溶体薄膜。通过X射线衍射(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)和荧光分析(FA)对所制备的薄膜进行了分析表征,研究了Ba摩尔分数对薄膜的晶相结构、表面形貌和发光性能的影响。结果表明,原电池法制备的Ba_(1-x)Ca_xMoO_4薄膜致密、均匀、结晶完好,为四方相结构。随着初始溶液中Ba含量的增加,所得Ba_(1-x)Ca_xMoO_4固溶体薄膜的形貌逐渐从CaMoO_4微晶的球形转变为BaMoO_4微晶的四方锥形。在290nm紫外光的激发下,制备的薄膜均在350nm和495nm附近呈现两个宽的发射带,其中495nm的蓝光发射明显强于350nm的紫光发射。初始溶液中的Ba/Ca的量比对所制备的Ba_(1-x)Ca_xMoO_4固溶体薄膜的发射光谱的形状和发射波长影响甚微,但对其发射强度有明显影响。     

Initial interaction of oxygen with aluminium single crystal faces: A LEED,AES and work function study

Auger electron spectroscopy (AES), low energy electron diffraction (LEED) and work function (Kelvin probe) measurements have been used to study the initial interaction of clean Al(111), (100) and (110) surfaces with oxygen at room temperature. The oxidation process was found to be surface orientation dependent, but a common feature has been always observed on the three low-index surfaces: they show two distinct phases, i.e. a chemisorbed phase followed then by an oxidized phase. From analysis of AES, LEED and Kelvin probe results, an adsorption mechanism of O on Al for each surface orientation is proposed.     

Über die Lebensdauer von elektrischen Gleichstrombögen im Ultrahochvakuum

The life time of de-arcs in vacuum was found to be determined by thin film effects on the cathode surface. By removal of surface contaminations in UHV the average arc duration was greatly enhanced. A further enhancement occurs by deposition of clean metal films. This is demonstrated for Mo on Cu-cathodes, and for Cu on Mo-cathodes. Hence compound materials like MoCu show an extreme high arc duration. The vapour pressure of the cathode material, however, has a minor influence. Therefore an arc between MoCu-electrodes emits more Mo- than Cu-vapour, as it is shown by mass analysis. Measurements of dc-field emission from arc cathodes (after the arc) show that the arc life time is correlated to the stability of field electron emission. The most intense field emitting sites are produced during the ignition of the arcs.     

微波电真空器件用热阴极的温度测量

利用红外测温仪、光学测温仪、热电偶测温仪(铂铑-铂)对微波电真空器件用浸渍阴极表面、覆膜阴极表面、阴极侧面（钼筒）进行了温度对比测试研究。结果表明:采用红外测温仪和光学测温仪测试浸渍阴极表面的温度与采用热电偶测温仪测试的温度相差不大,而覆膜阴极却相差约50 ℃;采用红外测温仪和光学测温仪测试阴极侧面（钼筒）的温度相差不大,都低于热电偶测温仪测试的温度约60 ℃,这说明红外和光学测试温度值低于阴极的实际温度（热电偶测量值）。由于在阴极表面出现了物理、化学变化,红外测温仪和光学测温仪测试的阴极表面温度值在1150 ℃左右加热100 min内增加约30 ℃。分析认为这些差异主要是因为覆膜阴极的表面与浸渍阴极的表面及阴极侧面（钼筒）的发射系数不同造成的,当然测试结果也会随着这些因素的变化而有一定的变化。     

GaAs真空电子源衰减模型研究

利用X射线光电子能谱(XPS)仪对激活后的GaAs真空电子源进行了随时间衰减变化的XPS分析,分析发现了电子源阴极表面各元素百分含量随时间的变化,揭示了杂质气体吸附造成的偶极矩方向的改变是电子源灵敏度显著下降的主要原因.基于上述结论,通过分析真空系统中杂质气体的吸附过程,推导并得到了GaAs电子源衰减模型.该模型从理论上揭示了GaAs电子源的指数衰减规律以及寿命与真空度的反比关系,与实验现象完全一致. 关键词： 电子源 X射线光电子能谱 衰减模型 真空度     

A study of Eu2O3, Sc2O3 co-doped tungsten matrix impregnated cathode

Eu₂O₃ and Sc₂O₃ co-doped W matrix impregnated cathodes have been prepared by the powder metallurgy method. The constitution of active elements on activated cathode surface is analyzed by in-situ Auger electron spectroscopy. It is found that although Eu exists in the matrix, no Eu is found on the cathode surface due to the formation of a stable Eu containing compound. Sc, Ba and O diffuse to the surface of the cathode and form an active surface layer during the activation period whereas the stable Eu-compound cannot liberate free Eu, which can diffuse from the cathode to the surface. The active substance of Sc, Ba and O on the cathode surface contribute to the emission property.     

Auger studies comparing the surface concentration of barium on tungsten impregnated and M-cathodes

A study comparing the surface concentration of barium on both an impregnated tungsten cathode surface and M-type cathode surface was made to determine whether the higher electron emission capability of the latter can be attributed to a higher average surface barium concentration. Relative quantitative data was obtained by the use of a computerized Auger microprobe spectrometer on the surface of the cathode, half of whose area was M-type, the other half being the tungsten impregnated type. The results indicate that both cathode surfaces have equivalent barium concentrations and that they are approximately equal to a barium monolayer after 3000 h of cathode life.     

亚微米电子发射材料的合成及发射性能

介绍一种气-液相合成技术合成多元碳酸盐及其制备阴极的发射性能.实验表明：采用该方法合成碳酸盐结晶小,形貌呈细丝状,丝径小于1μm,这种亚微米丝状碳酸盐能明显提高氧化物阴极的发射性能.通过对阴极激活后阴极表面的SEM分析,初步讨论了亚微米碳酸盐的发射机理. 关键词： 亚微米碳酸盐 气-液相合成技术 氧化物阴极 发射性能     

Experimental study on Ti N coated racetrack-type ceramic pipe

Ti N film was coated on the internal surface of a racetrack-type ceramic pipe by three different methods:radio-frequency sputtering, DC sputtering and DC magnetron sputtering. The deposition rates of Ti N film under different coating methods were compared. The highest deposition rate was 156 nm/h, which was obtained by magnetron sputtering coating. Based on AFM, SEM and XPS test results, the properties of Ti N film, such as film roughness and surface morphology, were analyzed. Furthermore, the deposition rates were studied with two different cathode types, Ti wires and Ti plate. According to the SEM test results, the deposition rate of Ti N/Ti film was about 800 nm/h with Ti plate cathode by DC magnetron sputtering. Using Ti plate cathode rather than Ti wire cathode can greatly improve the film deposition rate.     

脉冲高能量密度等离子体法制备TiN薄膜及其摩擦磨损性能研究

利用脉冲高能量密度等离子体技术在室温条件下在45号钢基材上制备出了超硬耐磨TiN薄膜.利用XRD，XPS，AES，SEM等手段分析了薄膜的成分及显微组织结构，并测试了薄膜的硬度分布及摩擦磨损性能.结果表明：薄膜主要组成相为TiN，薄膜组织致密、均匀，与基材之间存在较宽的混合界面；薄膜硬度高，在干滑动磨损实验条件下具有优异的耐磨性及较低的摩擦系数. 关键词： 脉冲高能量密度等离子体 TiN膜 显微组织 耐磨性     

钡钨阴极优化与热电子发射性能

分别从基体和铝酸盐两方面优化了钡钨阴极.在基体方面,首先采用窄粒度钨粉结合放电等离子体烧结获得了孔径分布窄的基体;再利用射频等离子体球化技术制备了球形钨粉,采用球形钨粉制备了多孔基体,获得了孔通道光滑、内孔连通性好、孔径分布更加窄的基体.与窄粒度钨粉基体相比,球形钨粉制备的阴极,空间电荷限制区的斜率由1.25增加至1.37,发射均匀性得到提高,拐点电流密度由6.6 A·cm^–2增至6.96 A·cm^–2.在此基础上,采用液相法改善了铝酸盐物相组成,发现空间电荷限制区的斜率增加至1.44,拐点电流密度增加至21.2 A·cm^–2.通过理论计算对钡钨阴极发射的物理本质进行了研究,发现钡钨阴极发射规律遵循偶极子理论.