Boundary-value problems in near-field optical microscopy and optical size resonances

We have solved a boundary-value problem for a ball probe interacting with a flat dielectric surface in an external optical radiation field. This interaction gives rise to the optical size resonance at frequencies significantly different from the natural frequencies of two-level atoms both in the medium and in the probe with allowance for the local field corrections. These resonances depend significantly on the distance from the probe center to the surface, on the ball probe size, on the concentration of two-level atoms in the probe and in the medium, on the spectral line width, and on the atomic inversion. The field strengths inside and outside the ball probe and a semiinfinite dielectric medium have been calculated in the near-field and wave zones. It is shown that the proposed electrodynamic theory of optical near-field microscopy agrees with the results of experimental measurements.     

On Auger electron spectroscopic measurements of ZnCl2 —coal interaction

By combining electron stimulated desorption (ESD) with low energy electron diffraction (LEED), Auger electron spectroscopy (AES) and work function change (Δφ) measurements the information content of ESD with regard to surface structure and composition is examined, using the surface systems O/W(100) and O/W(110). Although it is not possible to separate the local interaction from the ion escape phase, the comparison of the ESD results with Information derived from LEED, AES and Δφ and the use of simple models of the local interaction gives a rather detailed picture of the location and environment of adsorbed atoms which provides a reasonably reliable basis for the interpretation of UPS spectra of adsorption layers.ESD is extremely sensitive to adsorbed layers. The fact that the ion signal depends not only on coverage but also on the structure and structure-dependent properties of the adsorbate makes on the one hand coverage determination difficult if not impossible, on the other hand opens the door to structure analysis. The potential for obtaining structure information can be easily assessed by comparison with electron probe results.In comparison with other ion probes such as ion scattering spectroscopy and secondary ion mass spectroscopy, ESD is at present the most promising ion probe method for obtaining information on the location of adsorbed atoms from angular and energy distribution measurement (ESDIAD and ESDIED). This is clearly seen by the comparison with the structural data derived from LEED, AES and Δφ measurements for the complex system O/W(100). The consistency of the data obtained with ESD and electron probe techniques lends strong support to the simple models on which the analysis of the ESD results from chemisorbed layers are based. The comparison of ESD results from the system O/W(100) at high coverage and from O/W(110) with 0⁺ ion emission from oxides shows, however, that caution is in place when assigning ESD features to atoms chemisorbed on the metal surface. Without a careful analysis of the ion energy, threshold and/or cross-section such ions cannot be distinguished from ions produced by dissociation of oxides which may be present on the surface only in small quantity. These ions usually are not related to the chemisorbed species which covers most of the surface and therefore dominates the signals seen with (nearly) all other surface probes.If the consistency of LEED, AES, Δφ and ESD data for O/W(100) is not fortuitous, then ESD has already given some important feed-back to the electron probe techniques: the structural models derived from vibrational ELS spectra have to be revised. Increasing accumulation of experimental data and deepening of the theoretical understanding of the physical processes involved in ion emission will have to show how much further information complementary to that from electron probes can be obtained from ion probes.     

Single-body lensed photonic crystal fibers as side-viewing probes for optical imaging systems

We report the fabrication and performance of a lensed photonic crystal fiber (PCF) designed as a compact but effective side-viewing optical imaging probe. The lensed-PCF probe was implemented in a single body without using any other fibers or additional optics. The beam expansion region and a focusing ball lens, necessary for a focuser, were simultaneously formed along a small piece of PCF by applying arc discharges. The side-viewing ability was provided by polishing the ball lens with a femtosecond laser to form a total internal reflection surface. The working distance and the transverse resolution of the fabricated single-body lensed-PCF were experimentally measured to be 570 and 6.8 microm, respectively. With the proposed lensed-PCF probe, optical coherence tomography images of an in vitro biological sample were successfully obtained.     

飞行器GNSS接收机静电放电干扰效应分析

针对飞行器全球卫星导航系统接收机易受静电放电干扰的问题,研究了机体表面电晕放电与机务维修火花放电对接收机的干扰效应。分析了静电放电的时频域特征,使用针球电极与高压源组成的模拟器开展了电晕放电对接收机的前门耦合实验,证明了电晕脉冲产生的辐射场对接收机无明显干扰效应。基于人体金属ESD模型开展了火花放电对接收机的干扰效应实验,发现浪涌电流易导致接收机串口转换芯片电位波动,读写程序主循环卡死,应针对串口端进行静电阻抗器防护。     

静电放电火花产生的电磁场特征分析

静电放电(ESD)产生的电磁脉冲(EMP)会对电子系统的正常工作造成严重的干扰,甚至造成系统的损伤.故提出了一种修正的ESD火花电偶极子模型,并用此模型定性地分析了ESD火花产生的电磁场的特征,得出的-些结论对进一步研究ESD的电磁防护措施提供了有益指导.     

Comparison of ESD from metal sphere electrodes and tribocharged insulators of both polarities using two ESD probes

Electrostatic discharge (ESD) is an important source of accidental ignitions in process industries and damage to semiconductor electronic devices. There is a need to understand the time-varying ESD event and interaction between ESD probe and source in order to understand the important parameters in ESD measurements for evaluation of these phenomena.This paper compares measured peak current, waveform, risetime and charge transferred in ESD from charged isolated spherical conductors with and without a ground plane (spark), and triboelectrically charged polyethylene and polyamide samples (brush discharge). Measurements made using two recently developed ESD probes are compared.     

On the Boil-Off Time of Probe Surfaces in Plasmas

The time required for the melting of the surface of a glass-insulated probe inserted in a plasma is computed including the influence of plasma mass motion. This effect is relevant for probe measurements in moving current sheaths of electrical gas discharges. For dense plasma focus experiments, it is shown that the time of formation of a transition layer of evaporated material is shorter than the ion relaxation time in the plasma and the transit time of the current sheath by the probe position.     

Induction charging risk assessment: Charged board alike discharges to metal and human body

Charge can easily be induced on electronics or on other conducting parts if they are exposed to external electrical fields. In production facilities where sensitive electronics are handled, strong electrostatic fields should be avoided due to the risk of causing electrostatic discharges (ESDs) that could damage components. In electronics manufacturing this is usually achieved by grounding all conductors and removing all insulators from an ESD Protected Area (EPA) in the facility. However, it is not always possible to remove all insulators from the EPA as they are sometimes an essential part of the production processes. In this case, a method of risk assessment is necessary to evaluate safe operation. We have studied induction charging of a dummy PWB (Printed Wiring Board) through a grounded MOSFET transistor, by grounding it directly to metal or through the human body, when the PWB is exposed to a static electric field. The experimental setup can easily be turned into an induction charging probe by changing the MOSFET transistor to a low leakage current, high voltage capacitor of suitable size and measuring the voltage over this capacitor.     

Assessment of ESD threats to electronic components

Electrostatic discharge (ESD) is a major source of failures in electronic devices and products detected during manufacturing. Reduction of semiconductor element dimensions as well as implementation of new product and production technologies have made many devices extremely vulnerable to disturbances of electrostatic origin. Effective ESD damage prevention requires that ESD threats are carefully assessed and understood. This paper reviews new research results on electrostatic discharges as well as tools for the assessment of ESD threats to electronic components. Influences of the new results on the ESD control are discussed. There is a need to modify existing standards for the ESD control in electronics industry in order to meet challenges related to the manufacturing of future electronic products.     

Characteristics of electrostatic discharges from intermediate bulk container materials

In this work, we have studied experimentally electrostatic discharges from flexible or rigid intermediate bulk container (FIBC or RIBC, respectively) materials charged to both polarities. Four different kinds of materials were investigated, including woven polypropylene (PP) fabric, smooth-surfaced polypropylene sheet, smooth-surfaced polyethylene (PE) sheet and smooth-surfaced nylon sheet for comparison. Discharge peak current, charge transfer and distance from the surface at which a discharge occurred, with no earthed backplane, were measured over a range of surface potential values. According to the results, negative polarity discharges gave higher peak current and charge transferred values than positive polarity discharge of the same surface potential. The distance at which the discharge occurred increased with surface potential as expected. However, peak current and charge values were relatively constant over a range of surface potential.     

Current distribution in ESD diodes; Cross section corrections

The electron current distribution in diodes consisting of a rectangular crystal and an electron emitting filament parallel to and in front of it, used in several electron stimulated desorption (ESD) experiments has been determined by means of a dummy crystal constructed from uniformly transparent Lektromesh and a moveable, suitably constructed fine probe. It was found that for straight filaments the distribution was uniform along the narrow, but nearly triangular along the long dimension of the crystal. Calculated log signal versus time curves in ESD show considerable curvature, as often observed experimentally with such geometries. Filaments with a straight center, but coiled and shielded end sections provide uniform current distributions. When such filaments are used the curvature of the log signal versus time curves disappears for Kr desorption from W(110) but is still seen for oxygen desorption. The absolute fraction of filament current hitting the front surface of a crystal was also determined for various geometries by using a thin suppressor mesh in front of the dummy crystal. Cross sections for CO, O, and Kr ESD from W(110) were redetermined with a coiled end section filament. After correction for the fractions of current to the crystal and current non-uniformities previous results are in fairly reasonable agreement with the new values, except for the CO measurements of Leung, Vass, and Gomer, which are still high by a factor of 5. The new measurements permit a recalculation of excitation cross sections for neutral desorption. It is found that the latter are substantially smaller than corresponding gas phase values.     

Electron stimulated desorption: Principles and recent developments

A survey is given of the basic experimental findings in electron stimulated desorption and of the accepted theoretical model for their explanation. As an example for the test of the theory, the isotope effect in ESD of hydrogen on tungsten surfaces is described, which shows excellent agreement with the predictions of the model. The use of ESD as a surface probe is exemplified with recent work on hydrogen adsorption states on tungsten; the need for generalization of the one-dimensional model to three dimensions becomes clear in this case. Recent developments in theory (a quantum-mechanical treatment of the process) and experiment (promising measurements of the angular distribution of ionic ESD) are shortly discussed.     

气压对微束射频容性放电模式调制的研究

微束射频容性放电在纳米晶体颗粒等离子体增强气相合成有着潜在的应用前景.本论文利用ICCD、单反相机、高压探头和电流探头等对微束射频容性放电特性进行了实验诊断研究.结果发现:在纯氩气微束射频放电中,随着气压的增加,放电从辉光放电模式向多通道丝状放电模式转换;在99%氩/1%氢混合气体微束射频放电中,丝状放电模式消失,而是从低气压全空间分布的辉光放电模式,到中等气压向轴心收缩的辉光放电模式,最后到高气压的“环状”辉光放电模式;而在纯氢气微束射频放电中,随着气压的增加,放电模式直接从全空间分布的辉光放电模式向“环状”辉光放电模式转换.最后通过射频电场中电子加热、趋肤效应和气体热传导的共同作用解释了产生不同放电模式的物理机制.     

半椭球形和子弹头形光纤传感探头的耦合特性

 利用光路追踪程序，对于不同光纤参数条件下半椭球形和子弹头形光纤传感探头的耦合特性进行了研究。研究结果表明：对于半椭球形探头，当长短轴之比在1.15和1.3附近时存在一个耦合最佳结构；而对于子弹头形探头，仅变成圆形时为最佳。这两种探头容易制作，半椭球形探头的耦合效率高于子弹头形。     

一种静电放电模拟装置的设计

近年来,与静电放电(ESD)领域相关联的气体放电理论、材料科学和电测技术等新兴学科的不断研究和发展,已逐渐由实验科学阶段走向实际应用阶段。同时,人们也逐渐发现静电放电给人类造成的危害是十分惊人的,它不仅能够影响人类的正常生活,更是限制了自动化生产水平的提高。基于传统静电放电的模拟装置设备单一、功能局限,无法满足静电放电全方位、多用途的实验要求,为解决这一问题,设计和实现了包含电极模拟、方位变换、电路传输的完整的实验模拟装置。该装置主要由底座、支撑架、金属球、放电针、绝缘环、方位表盘等6部分组成,能够满足不同极化方向电磁场条件下的实验要求,同时还能够实现对不同高度、不同位置条件下的电磁场的基本极化方向进行判断识别。该系统具有一定的实验创新性和先进性,能够有效地满足各类电磁实验的需要,为研究电磁诱发静电放电实验提供了有力的硬件支持。     

Capacitance and surface charge distribution computations for a satellite modeled as a rectangular cuboid and two plates

This paper presents a method to evaluate the capacitance and the surface charge distributions of a satellite modeled as a structure consisting of a rectangular cuboid with two coplanar rectangular plates. The Charges accumulate on the satellite surfaces result destructive electrostatic discharges (ESD). Integral equations are formed by relating the unknown charge density on the metallic cuboid and the two rectangular plates to the potential on the surface of these bodies. The integral equations are solved using the Method of Moments (MoM) based on pulse function as basis functions and delta functions as testing functions. In order to apply MoM, the surfaces of the metallic bodies are discretized by using non-uniform rectangular subsections. The numerical data on capacitance of this structure have been presented. The key results are that the computational method is validated by computing the capacitance of a cuboid to be 73.46 pF/m, which is consistent with previous works. Faster convergence and shorter computational time are achieved using non-uniform subsections. And, as expected, the surface charge density diminishes at joints where the plates connect to the cuboid.     

Experimental investigation of large-volume PIA plasmas atatmospheric pressure

Large-volume atmospheric-pressure plasmas have been the subject of previous research as a laboratory simulation of ball lightning, but measurements of the plasma properties have been unavailable. The present investigation employed a non-resonant microwave chamber with a 1000-W microwave-source operating at 2.45-GHz frequency to produce large volume (up to 0.8 L) plasmas that persisted after microwave shutoff. A Langmuir probe was used to measure electron density and temperature, and the highest values measured were 10¹⁰ cm^-3 at 0.67 eV, respectively. Plasma lifetimes after microwave shutoff were also measured, using both a photocell and a video camera, and were found to average 200 ms. A working hypothesis of the formation of shared electron orbitals in dense gas discharges is put forth to explain this phenomenon     

Investigation on different ESD protection strategies devoted to 3.3 V RF applications (2 GHz) in a 0.18 μm CMOS process

ESD protection for radio frequency (RF) applications must deal with good ESD performance, minimum capacitance, zero series resistance and good capacitance linearity. In order to fulfill these requirements, different ESD protection strategies for RF applications have been investigated in a 0.18 μm CMOS process. This paper compares different ESD protection devices and shows that a suitable ESD performance target for RF applications (200 fF max, 2 kV HBM) can be reached with a diode network scheme. The optimization of the diodes is then a key point which is detailed. A trade-off has to be found between the ESD performance, the voltage drop during ESD and the parasitic capacitance. Poly as well as shallow trench isolation (STI) bounded diodes have been studied and it appears clearly that a solution based on poly bounded diodes is the best choice.     

Triboelectrification of materials used in tape heads

Triboelectrification of tapes by read/write heads can result in either increased error rates or permanent damage to the heads through electrostatic discharge (ESD) or electrochemical processes. In order to understand these phenomena, we have studied triboelectrification between tapes and different tape head materials used in magnetic tape storage drives. The triboelectrification phenomenon can be modeled as a Thevenin equivalent battery or current source whose magnitude is highly dependent not only on materials, but also on physical parameters such as tape speed, wrap angle, the direction of tape over asymmetric multi-material substrates, and the complete electrical circuit. In this report, we will discuss the different physical parameters that affect the tribocharging of tape by different tape and head materials. We also show that tribocharging can cause ESD damage.     

Influence of Surface Contaminations on Cathode Processes of Vacuum Discharges

The influence of surface contaminations on the ignition and maintenance of vacuum discharges is discussed qualitatively. Surface analysis of the electrodes and gas analysis during the discharges demonstrate that fresh electrodes contain always impurities within the upper surface layers, which affect the behaviour of vacuum arcs and vacuum breakdowns. The most effective way for cleaning the surfaces are the discharges themselves, if they burn in UHV. During that cleaning the following variations have been found: Are cathodes spots change from rapid moving ones with small erosion (type 1) to slow ones with strong erosion (type 2). The ignition of nanosecond discharges needs higher field strength and field emission current density. Polishing effects by short discharges (< 5 ns) become more pronounced. Erosion craters in nanosecond discharges increase.