Analysis for charged spacers in FED

Charged spacers in the field emission display (FED) are analyzed with the Monte Carlo method. The spacer is made of an insulator, which has generally a high secondary electron emission property. Under electron bombardment, the secondary electron emission induces charge on the spacer. We show that the surface of the spacer is charged positively in FED operation, which would cause an image distortion. We analyze the effect of charging on the spacer in terms of the electron density profile and luminescence profile of a dot near the spacer. Simulation results show that the image of a dot near the spacer is darker and smaller than that of a dot away from the spacer, though electrons are crowded near spacers. The results are confirmed by experiments. Finally, we suggest a way to reduce the effect of spacer charging by introducing a metal strip     

Silicide application on gated single-crystal, polycrystalline andamorphous silicon FEAs. I. Mo silicide

In order to improve both the level and the stability of electron field emission, the tip surface of silicon field emitters have been coated with a molybdenum layer of thickness 25 nm through the gate opening and annealed rapidly at 1000°C in inert gas ambient. The gate voltages of single-crystal silicon (c-Si), polycrystalline silicon (poly-Si) and amorphous silicon (a-Si) field emitter arrays (FEAs) required to obtain anode current of 10 nA per tip are 90 V, 69 V, and 84 V, respectively. In the case of the silicide emitters based on c-Si, poly-Si and a-Si, these gate voltages are 76 V, 63 V, and 69 V, respectively. Compared with c-Si, poly Si and a-Si field emitters, the application of Mo silicide on the same silicon field emitters exhibited 9.6 times, 2.1 times, and 4.2 times higher maximum emission current, and 6.1 times, 3.7 times, and 3.1 times lower current fluctuation, respectively. Moreover, the emission currents of the silicide FEAs depending on vacuum level are almost same in the range of 10^-9~10^-6 torr. This result shows that silicide is robust in terms of anode current degradation due to the absorption of air molecules     

Improvement of electron emission efficiency and stability bysurface application of molybdenum silicide onto gated poly-Si fieldemitters

As an approach to improve electron field emission and its stability, molybdenum (Mo) silicide formation on n⁺ polycrystalline silicon (poly-Si) emitters has been investigated. Mo silicide was produced by direct metallurgical reaction, namely, deposition of Mo and subsequent rapid thermal annealing. The surface morphologies and emission properties of Mo-silicided poly-Si (Mo-polycide) emitters have been examined and compared with those of poly-Si emitters. While anode current of 0.1 μA per tip could be obtained at the gate voltage of 82 V from poly-Si emitters, the same current level was measured at 72 V from Mo-polycide emitters. In addition, the application of Mo silicide onto poly-Si emitters reduced the emission current fluctuation considerably. These results show that the polycide emitters can have potential applications in vacuum microelectronics to obtain superior electron emission efficiency and stability     

Influence of electrical and structural parameters on the performance of the spacers in HOPFED

The HOPping Field Emission Display （HOPFED） is a new architecture for field emission displays. The main difference between a conventional Field Emission Display （FED） device and a ItOPFED lies in the spacer structure. In a HOPFED, two dielectric plates, named hop and flu spacer, are sandwiched between the emitter and the front plate. The objective of this spacer structure is to improve the performance oF a FED substantially with notable contrast, color purity and luminance uniformity. In order to optimize the structure of the device and to make the electron spot on the screen match the requirement of the phosphor dot dimension, the influence of electrical and structural parameters of the device on the electron spot profile was studied by numerical simulation in this paper. Monte Carlo method was employed to calculate the potential distribution inside hop and flu spacers due to secondary electrons mechanism plays an important role in HOPFED. The results indicated that the potential distribution in the spacers and spot profile depended strongly on the hop voltage, anode voltage and spacer＇s layout. This study may provide a useful theoretical support for optimizing the structure in HOPFED.     

Formation of Nanoislands on Conducting Poly(3,4‐ethylenedioxythiophene) Films by High‐Energy‐Ion Irradiation: Applications as Field Emitters and Capacitor Electrodes

Nanoislands have been fabricated on the surface of conducting poly(3,4‐ethylenedioxythiophene) (PEDOT) films doped with poly(4‐styrenesulfonate) (PSS) using high‐energy (≈ 1–3 MeV) Cl²⁺ ion irradiation. Scanning electron microscopy and atomic force microscopy confirm the direct formation of nanoislands with diameters ranging from 50 to 300 nm and heights ranging from 40 to 120 nm. From our analysis, we propose that the formation of nanoislands might be due to micelle formation of the polymeric stabilizer poly(sodium 4‐styrenesulfonate) (PSS‐Na) surrounding the nuclei in the PEDOT/PSS via the high‐energy‐ion irradiation. We observe similar results for high‐energy‐ion irradiated polyaniline doped with PSS‐Na. On using the nanoislands as nanotip emitters of a field‐emission display, an increase in the current density of about five orders of magnitude is observed. Cyclic voltammetry of the PEDOT/PSS electrode with the nanoislands as the electrode shows enhanced capacitance compared with that of the PEDOT/PSS film that contains no nanostructure.     

Improved field emission characteristic of carbon nanotubes by an Ag micro-particle intermediation layer

An efficient way to improve field emission characteristic of carbon nanotubes (CNTs) through an Ag micro-particle intermediation layer is presented. In this way, the intermediation layer is deposited on an indium tin oxide glass substrate by electrochemical method and then the CNTs are covered onto surface of the intermediation layer by electrophoretic method as CNT field emitters. The field emission characteristic of the CNT field emitters with the intermediation layer is significantly improved compared to the one without the intermediation layer, including decreased turn-on electric field from 4.2 to 3.1 V/μm and increased emission current density from 0.224 to 0.912 mA/cm² at an applied electric field of 6 V/μm. The improved field emission characteristic may be attributed to gibbous surface of the CNT field emitters. This efficient way is much simple, low cost, and suitable for production of large scale CNTs–based field emission cold cathode.     

加入支撑墙的FED的电场分布及电子轨迹数值模拟

ＦＥＤ内部真空中的电场和电子运动受到支撑结构的影响,为此采用了有限元法计算带有介质支撑墙的ＦＥＤ电场分布;采用龙格－库塔法计算该空间电子轨迹。并且在考虑了介质支撑墙上的二次电子发射之后。定性的分析了空间电场电子轨迹及墙上的电荷积累情况。得出了支撑墙对ＦＥＡ电子轨迹影响的数值结果,对器件的设计提出了建议。     

场致发射平板显示器的研究进展

利用碳纳米管作为阴极材料的场致发射显示器是一种新型的平板真空器件。介绍了二极管型和三极管型场致发射显示器的各种基本结构,给出了场致发射平板显示器的基本行列矩阵寻址方式原理,重点分析和讨论了在制作大面积平板器件方面所存在的支撑结构问题,这种新颖的平板显示技术将会进一步降低生产成本和提高显示质量。     

Fabrication and some applications of large-area silicon field emission arrays

A method of fabricating large-area arrays of sharply-pointed field emitters at densities up to 1·5 × 10⁵ per cm² from single crystal silicon wafers is described. The point emitters are formed by etch-undercutting a precision oxide pattern which is delineated on the silicon surface by projection photolithography. Observations indicate that emitters with very small tip dimensions in the 200Årange are formed. In the presence of an external electric field, such as produced by a voltage applied to a closely-spaced, planar anode, multiple-emitter arrays are shown to field-emit electrons uniformly over areas up to 3 cm dia. Two important applications currently being explored, are discussed: (1) High resistivity, p-Si has been utilized to develop experimental field emission photocathodes with which field emission imaging has been demonstrated. These photoemitters exhibit very high photo-sensitivities at visible and near i.r. wavelengths. For example, at 0·86 μm, the measured quantum efficiency is 25 per cent which is about five-times higher than the red-sensitive S-20 photocathode and comparable to the highest reported sensitivities of the III–V photosurfaces; (2) N-type emitter arrays show considerable promise as high current, cold cathodes and total emission currents of 1/4 A from 1 cm² areas of 100 Ω-cm n-type emitters have been obtained. Measurements were made under pulse conditions because of anode dissipation considerations.     

Improving single-mode VCSEL performance by introducing a longmonolithic cavity

We report on the improvement of several selectively oxidized vertical-cavity surface emitting laser characteristics by introducing a long monolithic cavity. The samples compared are grown with various cavity lengths using solid-source MBE. The 980 nm-regime is chosen as emission wavelength to facilitate growth by using binary GaAs cavity spacers. A record high single-transverse mode output power of 5 mW at a series resistance of 98 Ω is obtained for a 7-μm aperture device with a 4-μm cavity spacer. Using an 8-μm cavity spacer, devices up to 16-μm aperture diameter emit 1.7 mW of single-mode power with a full-width at half-maximum far-field angle below 3.8°     

Universal Bottom Contact Modification with Diverse 2D Spacers for High-Performance Inverted Perovskite Solar Cells

Although the 2D spacer modification is widely studied in perovskite solar cells (PVSCs), the energy level alignment between the 2D/3D interfaces makes it unfavorable for top surface passivation in the inverted p-i-n device structure. To address this issue, the effect of bottom interface modification is studied with three representative 2D spacers, i.e., the Ruddlesden-Popper 2D spacer, Dion-Jacobson 2D spacer, and strong passivation 2D spacer, in inverted p-i-n PVSCs. After optimization, the PVSCs with these 2D spacer modifications universally exhibit the best efficiencies of ≈21.6%, which constitutes dramatic improvement compared to the control device (20.7%). By lifting off the perovskite layer, the optoelectronic properties of the bottom surface are studied, and the mechanism underlying the improved device performance is unveiled to be uniformly originated from the formation of 2D/3D heterojunction, where the cascade valence band facilitates the hole collection and electron back scattering field suppresses the charge recombination at the anode interface. Besides, the unencapsulated device retains 90% of initial efficiency after 30 days of storage in ambient air with a relative humidity of 30 ± 5%, indicating excellent stability against moisture and oxygen. This study provides insight into the bottom interface modification with diverse 2D spacers for high-performance p-i-n structured PVSC devices.     

真空微电子器件应用研究

本文叙述了场致发射的机理及几种不同类型场致发射阴极的特点,并对场致发射技术在真空微电子器件方面的应用进行了分析.     

碳纳米管蒸发特性及其对场发射性能的影响

为了探究场发射阴极电流的跌落机制,采用四极质谱仪分析的方法研究高温蒸发对阴极场发射性能的影响。实验结果表明：碳纳米管阴极在1173 K以上温度时开始蒸发出碳;在1373 K高温下连续蒸发100小时,碳纳米管阴极的开启场强增加21.7%,阈值场强增加31.7%,增强因子减小16.2%,功函数增加11.9%。扫描电镜（SEM）和能量色散X射线光谱仪（EDX）分析显示：增大的功函数和减小的场增强因子降低了阴极的场发射性能。阴极材料的蒸发是阴极电流跌落的重要原因。     

用场发射显微镜测量单壁碳纳米管的逸出功

该文利用场发射显微镜对单壁碳纳米管的逸出功进行了研究和测量。未进行加热除气的单壁碳纳米管的表面吸附大量气体,此时测量的逸出功不是清洁表面单壁碳纳米管的逸出功。实验首先加热除气得到单壁碳纳米管的场发射清洁像,然后利用场发射显微镜测量I-V曲线,得到Fowler-Nordheim直线斜率;再利用透射电镜观测单壁碳纳米管微束形貌像,测量管束半径,通过三种公式估算比例因子,最后计算得到单壁碳纳米管的逸出功。     

Three-dimensionally confined excitons and biexcitons in submonolayer-CdSe/ZnSe superlattices

We report on structural and optical investigations of submonolayer-CdSe/ZnSe superlattices with varying thicknesses of the ZnSe spacer layers. High-resolution electron microscopy images demonstrate the formation of two-dimensional nanoscale CdSe islands for submonolayer-CdSe depositions. The vertical island arrangement is anti-correlated for spacer layer thicknesses exceeding 30Å, while predominantly vertically correlated growth occurs for thinner spacers. The different vertical ordering of the CdSe islands results in two clearly distinguishable lines in photoluminescence and optical reflectance spectra, which are attributed to excitons localized in quantum dots (QDs) formed by vertically coupled and uncoupled (Cd,Zn)Se islands, respectively. δ-like emission of single QDs is demonstrated and the different carrier localization in uncoupled and coupled QDs is reflected in the polarization of the edge emission. Stimulated emission and resonant waveguiding effects are observed for both states. At the highest excitation densities, we observe saturation of the stimulated emission in edge geometry attributed to saturation of localized states.     

Analysis of Failure in Miniature X‐ray Tubes with Gated Carbon Nanotube Field Emitters

We correlate the failure in miniature X‐ray tubes with the field emission gate leakage current of gated carbon nanotube emitters. The miniature X‐ray tube, even with a small gate leakage current, exhibits an induced voltage on the gate electrode by the anode bias voltage, resulting in a very unstable operation and finally a failure. The induced gate voltage is apparently caused by charging at the insulating spacer of the miniature X‐ray tube through the gate leakage current of the field emission. The gate leakage current could be a criterion for the successful fabrication of miniature X‐ray tubes.     

The Role of Self-Similarity in Fractal Photoconductive THz Emitters

We present the effect of self-similarity in fractal photoconductive THz emitters. The performance of fractal THz PC emitters are compared to those of non-fractal emitters, and their radiation properties are studied. It is demonstrated that the THz radiation emission enhancement results from the inherent fractal self-similarity and not only from the sub-wavelength apertures pattern present on the antenna’s surface. Through the application of this concept, photoconductive THz emitters having higher THz radiation power could be designed and fabricated.     

Electron translocation and field emission in printed CNT film by high-temperature sintering and post-treatment

The main problem of printed carbon nanotube film (CNTF) is that emitters do not have distributed uniformity. CNT was buried in leftover binding materials, which needs to be removed by fitted sintering and post-treatment. A new paste for printed CNTF was developed. Tunneling coefficients of leftover potential barrier were calculated respectively by the numerical method. The electrons translocation results through potential barrier between CNTs in calculated CNTF were tested by an experiment. A novel post-treatment, including high-temperature sintering and mechanical shearing and blowing, was performed to evidently improve the electron translocation and field emission current density of CNTF. Excellent emission prosperities were exhibited: stable current density, distributed uniformity emitters and long lifetime. The treatment of high-temperature sintering and mechanical shearing and blowing, may be an important prerequisite for future field emission display.     

场致电子发射技术分析

本文介绍了发射的机理致发射的几种不同类型的阴极,叙述了类金刚石薄膜作为场致发射阴极的优点,最后对场致发射的应用进行了分析。