Improvements to differential voltage contrast and light and electron scanning beam analysis of solar cells

Differential voltage contrast (DVC) in conjunction with light and electron beam scanning (LEBEAMS) technique were used for measuring the electric potential, field, and charge distribution in solar cells. The DVC is based on enhancement or retardation of secondary electron emission, generated by an electron beam, due to local changes in the potential of a semiconductor device. The information provided by this technique is invaluable to the development of any device. Solar cells have been studied by the DVC technique, both under electrical bias (DVC) and under illumination (DVC in conjunction with LEBEAMS); however, the conditions of the previous did not replicate the normal illumination conditions of a solar cell. The goal of this research was to redesign and expand the previous LEBEAMS experiments to produce accurate profiles of quasi Fermi energies on solar cells.     

Experimental analysis and computer simulation of a methodology for laser focusing in the solar cell characterization by laser beam induced current

This paper presents a quick methodology for focusing a laser beam on a photoactive surface based on performing a single line scan while simultaneously modifying the laser's position over the surface and the distance between the focusing lens and the active surface. The methodology was tested using the computer simulation technique. Several configurations were computer simulated by programming different experimental situations to discover the situations in which this focusing methodology would provide optimum results. The conclusions obtained from computer simulation methodology were checked by means of experimental tests using several solar cells, such as a thin-film amorphous silicon solar cell, a monocrystalline silicon solar cell, and a polycrystalline silicon solar cell. From the tests performed, we concluded that optimum focusing is achieved in systems in which the laser beam induced current signal generated by the photoactive surface has no large heterogeneities (e.g., fingers or grain boundaries), artefacts, or defects. Thus, the best results are achieved in systems where the surface of the photovoltaic device has a certain degree of homogeneity.     

X-ray beam induced current method at the laboratory x-ray source

The x-ray beam induced current method (XBIC) is realized on the laboratory x-ray source using the polycapillary x-ray optics. It is shown that rather good images of grain boundaries in Si can be obtained by this method. The parameters of x-ray beam are estimated by the simulation of Schottky diode image. A good correlation between the experimental and calculated grain boundary XBIC contrast is obtained. The possibilities of laboratory source based XBIC method are estimated.     

Recording transmitted beam current for X-ray microanalysis in a scanning transmission electron microscope

A method of measuring transmitted beam current stability during and between X-ray microanalyses in a STEM is described. This facility also allows analytical artefacts due to charging, drift, contamination and mass loss to be detected during an analysis.     

恒光强扫描干涉光刻条纹锁定系统设计

为提高扫描干涉光刻机的加工效率和加工精度、扩大加工范围、降低维护成本,提出了一种可实现干涉条纹周期、方向和相位同步实时调节控制的扫描干涉光刻机系统方案,并着重介绍了最为关键的恒光强干涉条纹相位锁定系统的设计.首先,介绍了扫描干涉光刻中干涉条纹周期、方向和相位同步实时调节控制的扫描干涉光刻机系统原理方案,并设计实现了恒光...     

扫描式氙灯太阳模拟器十维扫描系统

为了模拟卫星在轨全年的太阳辐照情况,检验、优化整星的杂散光抑制能力,分析了光学载荷的在轨成像条件,设计了一种基于7维扫描镜+2维折反镜+1维被测样件共计10维运动机构的扫描式氙灯太阳模拟器,并建立了它们关于照明姿态和位置的控制方程,完成了被测样件的空间环境模拟照明。实验表明,对1 700mm×2 700mm的被测样件可实现方位角为-90°~+90°、俯仰角为-29°~+42.5°的模拟照明,角精度分别可达0.2°和0.1°,位置精度优于10mm。该扫描式太阳模拟器可较精确地为部分卫星提供全年太阳照明空间环境模拟实验。     

Investigation of photoconductivity of silicon solar cells by a near-field scanning microwave microscope

The photovoltaic effect in silicon solar cells were investigated by using a near-field scanning microwave microscope (NSMM) technique by measuring the microwave reflection coefficient at an operating frequency near 4 GHz. As the photoconductivity in the solar cells was varied due to the incident light intensities and the wavelength, we could observe the photoconductivity changes at heterojunction interfaces inside the solar cells by measuring the change of reflection coefficient S₁₁ of the NSMM. By measuring the change of reflection coefficient, we also directly imaged the photoconductivity changes at heterojunction interfaces inside the solar cells.     

In situ electron beam induced current measurements of the local thickness in semiconductor devices

A quantitative electron beam induced current method is shown, applicable in situ for electron beam current measurement on a semiconductor sample without the need for a Faraday cup. As a validation technique, the measurement of top overlayer thickness in the semiconductor structure was chosen for two reasons. First, the measured thickness is easily verified using the same electron microscope in the secondary electron mode by measuring the layer thickness at the layer edges. Second, the measurement of a layer thickness and its local variations constitute an important issue in semiconductor processing and characterization. The proposed method is used in the planar view of the sample, and also for locations far from the layer edges. Quasi‐three‐dimensional maps of the thickness spatial distribution are presented.     

Electron-acoustic and surface electron beam induced voltage signal formation in scanning electron microscopy analysis of semiconducting samples

The conditions for the detection of electron-acoustic (EA) and surface electron beam induced voltage (SEBIV) signals using a common sample mount and bottomside detection scheme are hereby discussed. It is shown that while the intrinsic properties of the sample under electron-beam irradiation would chiefly determine the presence of these contrast mechanisms, the manner in which the sample is mechanically and electrically configured in relation to the signal detection is crucial in determining the actual signal coupling mechanisms at work and hence the assumptions by which a robust and consistent interpretation of experimental results can be made. EA signals are detectable only if electrical coupling between the sample and the detector is defeated, a necessary pre-requisite as the signal magnitude of carrier-generated SEBIV coupling is 2-3 orders larger in most cases. With regards to SEBIV detection, bottomside SEBIV detection may be preferable to topside detection owing to minimization of topographic signal contribution, higher signal coupling efficiency and a less complex sample-detector mounting procedure.     

Autoschizis of human ovarian carcinoma cells: scanning electron and light microscopy of a new cell death induced by sodium ascorbate: menadione treatment

Human ovarian carcinoma (MDAH 2774) cells were treated with sodium ascorbate (VC), menadione (VK3), or a combination of both in a ratio 100:1 for 1h and then examined with scanning electron microscopy (SEM) and light microscopy (LM). Light microscopy data corroborated SEM observations, which demonstrated that death of VC+VK3-treated tumor cells occurred primarily by autoschizis. This type of cell death is characterized by a decrease in cell size, cytoplasmic self-excisions, and nuclear and nucleolar morphologic degradations without the formation of apoptotic bodies. Ultimately, cell death results from karyorrhexis and karyolysis. This study illustrates that plasma membrane damage (branching filopodia, blisters, blebs) results from VC treatment; cytoskeletal damage and self-morsellation are caused by VC, VK3 and VC+VK, treatments. The VC treatment results in a 23% decrease in cell diameter while VK3-treated cells decrease cell diameter by 66%. After 1h of VC+VK3 treatment, a heterogenous cell population is found. This population can be resolved into one population whose diameters are 23% smaller than those of sham-treated cells, and a second population whose diameters are approximately twice those of sham-treated cells. This second population is indicative of doublet formation in which the cells appear to be dividing (an early stage of autoschizic cell death). One half of the doublet contains the cell nucleus while the other half consists of cytoplasm and membrane only. The enucleate portion of this doublet will then be excised. When the types of cell death are enumerated following VC+VK3 treatment, 43% of the cells die by autoschizis, 3% by apoptosis, and 1.9% by oncosis. These results confirm that autoschizis is the principal form of cell death that results from the in vitro treatment of human ovarian carcinoma cells with the vitamin combination.     

Nonlinear saturation controller for vibration supersession of a nonlinear composite beam

In this paper, a study for nonlinear saturation controller (NSC) is presented that used to suppress the vibration amplitude of a structural dynamic model simulating nonlinear composite beam at simultaneous sub-harmonic and internal resonance excitation. The absorber exploits the saturation phenomenon that is known to occur in dynamical systems with quadratic non-linearities of the feedback gain and a two-to-one internal resonance. The analytical solution for the system and the nonlinear saturation controller are obtained using method of multiple time scales perturbation up to the second order approximation. All possible resonance cases were extracted at this approximation order and studied numerically. The stability of the system at the worst resonance case (Ω = 2ω _s and ω _s = 2ω _c ) is investigated using both frequency response equations and phase-plane trajectories. The effects of different parameters on the system and the controller are studied numerically. The effect of some types of controller on the system is investigated numerically. The simulation results are achieved using Matlab and Maple programs.     

高斯光束横向光强分布的检测研究

由于激光技术的广泛应用和不断发展,对高斯光束的研究及测量成为一个重要内容。高斯光束横向光强分布的特性直接关系到激光的应用,因此从高斯光束横向光强分布特性的研究出发,采用小孔扫描法和CCD数据采集法测量高斯光束横向光强分布,然后把实验测量的光强分布数据通过图像处理程序绘制成光强分布曲线并与理论的高斯分布曲线进行拟合对比。结果显示实验测得的高斯光束的横向光强分布与理论高斯分布吻合,证实了高斯光束的横向光强分布遵守高斯函数。     

电流互感器磁饱和裕度间接测量法的研究

在认真分析JJG 1021—2007《电力互感器》检定规程规定的磁饱和裕度测量方法和检定原理的基础上指出了原方法存在的难点,提出了通过间接法测量电流互感器误差和应用传统比较法测量电流互感器误差,结合励磁导纳测试的新方法来测量电流互感器的磁饱和裕度,方法简单,同时保证了测试的准确性。     

Multi-field 3D scanning light microscopy of early embryogenesis

A computer‐controlled microscopy system was devised to allow the observation of avian embryo development over an extended time period. Parallel experiments, as well as extended specimen volumes, can be recorded at cellular resolution using a three‐dimensional scanning procedure. The resulting large set of data is processed automatically into registered, focal‐ and positional‐drift corrected mosaic images, assembled as montages of adjacent microscopic fields. The configuration of the incubator and a sterile embryo chamber prevents condensation of the humidified culturing atmosphere in the optical path and is compatible with both differential interference contrast and epifluorescence optics. As a demonstration, recordings are presented showing the large‐scale remodelling of the embryonic primordial vascular structure.     

光的偏振在电流传感器中的应用

传统电流互感器在大电流测量中存在绝缘和安全等方面的问题,而煤矿井下电磁干扰强,负载情况比较复杂,安全要求更加严格,因此作者利用光的偏振原理,设计了磁光电流传感器系统.该系统具有很强的电气绝缘和抗电磁干扰能力.系统传感器由脉冲光源发出的光经Faraday盒变成调制光,再经光电转换、带通滤波、同步解调、低通滤波电路后由单片机实现对电流信号实时采集,从而实现对井下电流实时准确地测量.     

Automatic measurement of scanning beam diameter using an on-line digital computer

A method for the measurement of electron probe beam diameter by digital image processing has recently been published. The purpose of the present report is to describe the development of an automatic system for beam diameter measurement. To complete this system, a method based on a theory which combines automation and high-resolution conditions is proposed. In practice, the beam diameter is measured from the STEM image of a crystalline hole in a gold thin film, utilizing an on-line computer system equipped with newly developed digital processing programs linked to a SEM in the transmission mode. The functions of the programs include statistical processing, matching, noise removal, interpolation, selection, and rotation. By combining these functions, the scanning beam diameter is accurately measured, in spite of difficulties, under most electron microscope operating conditions. The user simply appoints the edge included in the STEM image.     

基于扫描线数据自由曲面在AutoCAD中的构建

这里提出一种AutoCAD环境下自由曲面的三维重建方法,根据测量得到的三维扫描线数据,通过反算得到控制顶点,用Add3Dmesh方法在AutoCAD中创建双三次B样条曲面实现了自由曲面三维模型的自动重建,提高了自由曲面建模和设计的效率。     

Focused ion beam/scanning electron microscopy studies of Porcellio scaber (Isopoda, Crustacea) digestive gland epithelium cells

The focused ion beam (FIB) was used to prepare cross sections of precisely selected regions of the digestive gland epithelium of a terrestrial isopod P. scaber (Isopoda, Crustacea) for scanning electron microscopy (SEM). The FIB/SEM system allows ad libitum selection of a region for gross morphologic to ultrastructural investigation, as the repetition of FIB/SEM operations is unrestricted. The milling parameters used in our work proved to be satisfactory to produce serial two-dimensional (2-D) cuts and/or three-dimensional (3-D) shapes on a submicrometer scale. A final, cleaning mill at lower ion currents was employed to minimize the milling artifacts. After cleaning, the milled surface was free of filament- and ridge-like milling artifacts. No other effects of the cleaning mill were observed.