Investigation of range-energy relationships for low-energy electron beams in silicon and gallium nitride

The electron beam technique of the Scanning Electron Microscopy (SEM) has been widely used for the characterization of bipolar devices and photodiode materials. The resolution of an electron beam technique is affected by the interaction of the beam and the specimen. The size of this interaction volume, commonly termed the generation volume, is usually characterized by what is called the electron penetration range and is measured from the surface. Since there is currently no consensus on the expressions to use in the calculation of the electron range, this paper provides an analysis of the three most commonly used semiempirical expressions. They are the Gruen range, the universal curve of Everhart and Hoff, and the maximum range of Kanaya and Okayama. This analysis is done using data from the statistical method of Monte Carlo simulations. It was found that the Everhart and Hoff universal curve performs better at low beam energies than the equation of Kanaya and Okayama. However, the validity of all the three expressions is questionable below 5 keV. In order to overcome this, fitted expressions based on the extrapolated range are provided for beam energies below 5 keV in the case of Si and GaN materials. The accuracy of these expressions is affected by the physical parameters used in the Monte Carlo simulations.     

Angle-resolving time-of-flight electron spectrometer for near-threshold precision measurements of differential cross sections of electron-impact excitation of atoms and molecules

This article presents a new type of low-energy crossed-beam electron spectrometer for measuring angular differential cross sections of electron-impact excitation of atomic and molecular targets. Designed for investigations at energies close to excitation thresholds, the spectrometer combines a pulsed electron beam with the time-of-flight technique to distinguish between scattering channels. A large-area, position-sensitive detector is used to offset the low average scattering rate resulting from the pulsing duty cycle, without sacrificing angular resolution. A total energy resolution better than 150 meV (full width at half maximum) at scattered energies of 0.5-3 eV is achieved by monochromating the electron beam prior to pulsing it. The results of a precision measurement of the differential cross section for electron-impact excitation of helium, at an energy of 22 eV, are used to assess the sensitivity and resolution of the spectrometer.     

A real-time optical image projection system for electron microscopy

The Hughes liquid crystal light valve has been coupled to a transmission electron microscope using a fibre optics plate and transmission phosphor. This system makes it possible to reconstruct in real time, electron images in coherent or incoherent light of arbitrary intensity outside the vacuum. The experimental results reported are used to estimate the design parameters of an on-line coherent optical diffractometer for high resolution work.     

A method for preparing cross sections of films on wear surfaces for transmission electron microscopy study

A method for preparing cross sections of surface layers which exist on bulk metal substrates for transmission electron microscopy (TEM) study is described. The surface layer or film is protected by a vacuum-deposited or sputtered coating of a suitable metal. A mask is placed over the surface and non-masked areas are subjected to ion beam etching until the substrate is exposed. A thick electroplated layer is then applied to the surface. This layer adheres well to the ion-etched substrate and seals the coated surface film against damage during the usual slicing and grinding steps which are required for the preparation from bulk materials of thin foils for TEM study. The method was developed specifically for the analysis of boundary and extreme pressure lubrication films on wear surfaces together with the near-surface region of the substrate. However, it is also applicable to the investigation of oxide, corrosion and other surface films.     

Suprathermal plasma analyzer for the measurement of low-energy electron distribution in the ionosphere

It is commonly believed that an energy transfer from thermal to suprathermal electrons (相似文献   

Observation of current-density filamentation in multilayer structures by EBIC measurements

The total current-voltage characteristics of the p⁺-n⁺-p-n^? and n⁺-p-n-p^? diodes under investigation show branches of negative differential resistance. Accompanied by the appearance of negative differential resistance is a filamentation of current-density and electric-field distribution. Electron beam-induced current (EBIC) measurements were used to examine the properties of filamentation from the point of view of self-organized pattern formation. Besides the detection of the spatial distribution of the electric field, EBIC measurements give information on current-density filamentation. Furthermore, the perturbation by the electron beam gives information on the dynamic behavior of the filamentary structure.     

Analysis methodology of movable emittance-meter measurements for low energy electron beams

The design of photoinjectors for modern free electron laser linac relies heavily on particular beam behavior in the few meters after the gun. To experimentally characterize it a movable emittance meter was proposed and built [L. Catani et al., Rev. Sci. Instrum. 77, 093301 (2006)] based on the beam slicing technique. This paper addresses all the aspects of analysis of the data acquired with the emittance meter and common to any slit based emittance measurement for low energy beams.     

Preparation of cross sections of thin-coated sheet steel for analytical electron microscopy observation

A method of preparing thinned cross sections of coated sheet steel (Galvalume) for observation in an analytical electron microscope (AEM) was developed. Steel panels dipped for 4 sec in baths of 55% by weight (wt pct) Al-1.7 wt pct Si-balance Zn, and 55 wt pct Al-6.88 wt pct Si-balance Zn at 610°C were examined. The ratio of the intensity of the K and L x-ray lines from the same element was used in determining the foil thickness. The AEM results compared favorably to results obtained using electron microprobe analysis (EMPA).     

电子束焊接温度场实时监测系统设计

焊接温度场是影响焊接质量和生产效率的主要因素,因此对焊接过程中的温度场分布进行监测就显得极为重要。利用普通彩色CCD构成了焊接温度场实时测量系统;基于工件热辐射随温度变化单调上升特性建立了温度场测量模型;采用最小二乘法对实测的温度数据进行分析,得到了温度场测量模型的最佳参数。试验结果表明了该监测系统的可行性。     

基于CDMA的配电变压器实时监控系统

本文提出构建基于CDMA的配电变压器实时监控系统,通过监测终端实时采集配电线路上变压器的运行参数,以CDMA通信方式传送至监控中心,在监控中心对这些信息进行运算处理,对配变进行远程控制,保证配电变压器的安全运行和经济运行.     

A setup for measuring total cross sections of nuclear reactions

An experimental technique and a setup for measuring the energy dependence of the total cross sections of nuclear reactions with stable and radioactive nuclear beams at kinetic energies approaching the Coulomb barriers are described. The modified transmission method, complemented with ??-ray detection in the 4?? geometry and pulse-shape discrimination of particles by a semiconductor detector, is used.     

Application of a low-energy electron beam as a tool of nondestructive diagnostics of intense charged-particle beams

A new diagnostic instrument intended for measuring the parameters of intense bunches, detecting radiation fields, and performing tomography of intense ion beams is described. The operating principle of the device and the basic scheme of arrangement of its elements are described. The results of simulation of a EBP for several problems are presented. To reconstruct the longitudinal charge-distribution function, the effect detection error of the testing beam on the accuracy of the proposed method is considered. Depending on the problem to be solved, several design versions of the instrument are proposed, which are optimized for diagnosing beams of S-range linear accelerators, detecting radiation fields, studying bunches of superhigh intensity, performing tomography of intense proton beams, and operating in cyclic accelerators.     

Acoustic-emission testing of solebars with boxlike cross sections

The changes in the design of the 18–578 solebar with a boxlike cross section required the development of a new scheme of arrangement of acoustic-emission (AE) transducers and improvement of both technique and software. All sources that were detected during AE testing were divided according to their degree of hazard into passive and critically active ones. Location grids that specified the rejection levels were imposed on the tested zones under study. In the refined technique, linear location was used, which made it possible to preserve the reliability of the investigation results and reduce the labor intensiveness of the AE testing.     

Explicit equations for critical depth in open channels with complex compound cross sections. A discussion

In open channel hydraulics, the notion of critical flow conditions and critical depth are not restricted to open channel flows with hydrostatic pressure distributions. This contribution shows an extension of the concept of critical flow conditions linked with the minimum specific energy, as introduced by Bakhmeteff [1] and extended by Liggett [9] and Chanson [5]. It demonstrated that the critical depth may be defined more broadly including when the pressure field is not hydrostatic.     

A study of the spinning force of hollow parts with triangular cross sections

The noncircular spinning is one of the recent breakthroughs of the traditional spinning processes. The spinning force is one of the important parameters for designing the spinning equipment and one of the main factors influencing the forming quality of spun parts. The variation of spinning force during noncircular spinning is considerably different from that of the conventional spinning due to the high-speed reciprocating movement of the roller induced by the variable spun workpiece profile. This paper presents an experimental investigation of spinning force characteristics of a hollow part with triangular cross sections using an octagon ring transducer based on electrical measuring method. A series of experiments using profiling driving spinning method was carried out to study the effects of the main process parameters, such as the roller feed rate, blank thickness–diameter ratio, and mandrel rotational speed, on the spinning force characteristics. The important characteristics of the force components of noncircular spinning were discussed based on the electrical measuring results. Furthermore, the variations of force components were compared with those obtained in the cases of conventional spinning and 3D non-axisymmetrical spinning. The results show that different from the conventional spinning and similar to the 3D non-axisymmetrical spinning, the three components of spinning force along the axial, radial, and tangential direction of roller vary periodically with the mandrel rotational angle. Different from the conventional and the 3D non-axisymmetrical spinning, the maximum spinning force is related to the mandrel rotational speed, even if the feed rate of roller remains constant, and increases with the increase of the mandrel rotational speed.     

A magnetic transport electron spectrometer for in-beam measurements

A compact magnetic transport electron spectrometer has been built having an overall efficiency of 0.92%, a resolution Δp/p of 18% and a maximum transmitted energy of 3 MeV. Limitations to accuracy in intensity measurements due to non-isotropic electron angular distributions have been discussed.     

A facility for measuring the static characteristics of high-intensity electron beams

The operating principle of a versatile facility for measuring the static parameters of high-intensity electron beams is based on detecting transient radiation produced by ribbon-shaped and axially symmetric electron beams incident on a metal target. Schemes for detection of transient radiation are discussed, and features of the measurement procedures suitable for particular beam configurations are described. For the first time, the design of an analyzer of ribbon-shaped electron beams is presented. The usability of the facility is confirmed by experimental results and numerical calculation.     

A forevacuum plasma source of pulsed electron beams

A plasma electron source designed for generation of a pulsed wide-aperture electron beam in the forevacuum pressure range (5–20 Pa) is described. The source is based on the use of a hollow-cathode glow discharge. At an accelerating voltage of 20 kV, a current pulse length of 100 μs, and a pulse repetition rate of 10 Hz, the electron beam current is 100 A, and the maximum density of the beam pulse power is 10 J/cm². The obtained parameters of the electron beam and the features of the source functioning in the forevacuum pressure range show that this source can be used to good effect to modify the surface properties of nonconducting materials.     

A digital modification for beam current measurements in electron microscopy

A digital microammeter with 0.1 μA sensitivity has been employed in the TEM beam current circuit to increase the accuracy to which the electron beam can be recorded and adjusted.