共查询到20条相似文献，搜索用时 15 毫秒
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J. CAZAUX 《Journal of microscopy》2005,217(1):16-35
In addition to improvements in lateral resolution in scanning electron microscopy, recent developments of interest here concern extension of the incident beam energy, E0, over two decades, from ≈ 20 keV to ≈ 0.1–0.5 keV and the possibility of changing the take-off emission, α, of detected secondary electrons. These two degrees of freedom for image acquisition permit a series of images of the same field of view of a specimen to be obtained, each image of the series differing from the others in some aspect. The origins of these differences are explored in detail and they are tentatively interpreted in terms of the change in the secondary electron emission yield δ vs. E0, δ = f(E0), and also of the change in δ vs. α, ∂δ/∂α. Various origins for the chemical contrast and topographic contrast have been identified. Illustrated by correlating a secondary electron image and a backscattered electron image, use of the scatter diagram technique facilitates image comparison. The difference between the lateral resolution and the size of the minimum detectable detail is outlined to avoid possible errors in nanometrology. Some aspects related to charging are also considered and possible causes of contrast reversal are suggested. Finally, the suggested strategy consists of the acquisition of various images of a given specimen by changing one parameter: primary beam energy and take-off angle for conductive specimens; working distance or beam intensity for high-resolution experiments; scanning frequency for insulating specimens. 相似文献
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Wei Zhang 《Scanning》2013,35(4):261-264
In an ultra‐high vacuum scanning electron microscope, the edged branches of amorphous carbon film (～10 nm thickness) can be continuously extended with an eye‐identifying speed (on the order of ～1 nm/s) under electron beam. Such unusual mobility of amorphous carbon may be associated with deformation promoted by the electric field, which resulted from an inner secondary electron potential difference from the main trunk of carbon film to the tip end of branches under electron beam. This result demonstrates importance of applying electrical effects to modify properties of carbon materials. It may have positive implications to explore some amorphous carbon as electron field emission device. SCANNING 35: 261‐264, 2013. © 2012 Wiley Periodicals, Inc. 相似文献
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Petr Schauer 《Microscopy research and technique》2022,85(5):1870-1883
The purpose of this paper is to find some general rules for the design of robust scintillation electron detectors for a scanning electron microscope (SEM) that possesses an efficient light-guiding (LG) system. The paper offers some general instructions on how to avoid the improper design of highly inefficient LG configurations of the detectors. Attention was paid to the relevant optical properties of the scintillator, light guide, and other components used in the LG part of the scintillation detector. Utilizing the optical properties of the detector components, 3D Monte Carlo (MC) simulations of photon transport efficiency in the simple scintillation detector configurations were performed using the computer application called SCIUNI to assess shapes and dimensions of the LG part of the detector. The results of the simulation of both base-guided signal (BGS) configurations for SE detection and edge-guided signal (EGS) configurations for BSE detection are presented. It is demonstrated that the BGS configuration with a matted disc scintillator exit side connected to the cylindrical light guide without optical cement is almost always a sufficiently efficient system with a mean LG efficiency of about 20%. It is simulated that poorly designed EGS strip configurations have an extremely low mean LG efficiency of only 0.01%, which can significantly reduce detector performance. On the other hand, no simple nonoptimized EGS configuration with a light guide widening to a circular or square profile, with a polished cemented scintillator and with an indispensable hole in it has a mean LG efficiency lower than 6.5%. 相似文献
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A device has been developed and used successfully on two models of the environmental scanning electron microscope that allows low-magnification imaging of about 30x, significantly better than the original 200x low-magnification imaging limit. This was achieved by using an additional aperture to limit the pressure at a point where it will not block the electron beam, and a larger aperture plate for the combination final aperture/secondary electron signal collection surface that also does not block the electron beam significantly. 相似文献
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Electron yield was measured from patterned carbon nanotube forests for a wide range of primary beam energies (400–20,000 eV). It was observed that secondary and backscattered electron emission behaviors in these forests are quite different than in bulk materials. This seems to be primarily because of the increased range of electrons due to the porous nature of the forests and dependent on their structural parameters, namely nanotube length, diameter and inter‐nanotube spacing. In addition to providing insight into the electron microscopy of nanotubes, these results have interesting implications on designing novel secondary electron emitters based on the structural degrees of freedom of nanomaterials. SCANNING 31: 221–228, 2009. © 2010 Wiley Periodicals, Inc. 相似文献
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For studying the electrical properties (charge trapping, transport and secondary electron emission) of the polypropylene‐based nanocomposites with different contents of natural clay, the specimens were submitted to electron irradiation of a scanning electron microscope. A device, suitably mounted on the sample holder of the scanning electron microscope, was used to measure two currents (i.e. leakage and displacement currents) induced in the polypropylene‐based nanocomposites (polymer nanocomposites) under electron irradiation. The evolution of trapped charge during irradiation for each type of studied polymer nanocomposites is deduced. The amount of trapped charge at the steady state is also determined by measuring the change of secondary electron image size associated to the electron trajectory simulation. It is found, surprisingly, that not only the leakage current increases as a function of clay loading level but also trapped charge. However, this could be related to the increase of conductivity in one hand and to proliferation of interfaces between nanoparticles and neighbouring materials on the other hand. These two processes play crucial role in controlling the carrier transport (through polymer nanocomposites or/and along its surface) closely related to the charge storage and leakage current. Additional experiment using dielectric spectroscopy were performed to show the effect of clay concentration in changing the dielectric relaxation behaviour and to evidence the existence of interfaces between nanoparticles and polymer. The secondary electron emission during electron irradiation is also studied through the total electron yield that is deduced by correlating the measured leakage and displacement currents. 相似文献
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We present results obtained with a new scintillation detector of secondary electrons for the variable pressure scanning electron microscope. A detector design is based on the positioning of a single crystal scintillator within a scintillator chamber separated from the specimen chamber by two apertures. This solution enables us to decrease the pressure to several Pa in the scintillator chamber while the pressure in the specimen chamber reaches values of about 1000 Pa (7.5 Torr). Due to decreased pressure, we can apply a potential of the order of several kV to the scintillator, which is necessary for the detection of secondary electrons. Simultaneously, the two apertures at appropriate potentials of the order of several hundreds of volts create an electrostatic lens that allows electrons to pass from the specimen chamber to the scintillator chamber. Results indicate a promising utilization of this detector for a wide range of specimen observations. 相似文献
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This article presents a pixellated solid‐state photon detector designed specifically to improve certain aspects of the existing Everhart–Thornley detector. The photon detector was constructed and fabricated in an Austriamicrosystems 0.35 µm complementary metal‐oxide‐semiconductor process technology. This integrated circuit consists of an array of high‐responsivity photodiodes coupled to corresponding low‐noise transimpedance amplifiers, a selector‐combiner circuit and a variable‐gain postamplifier. Simulated and experimental results show that the photon detector can achieve a maximum transimpedance gain of 170 dBΩ and minimum bandwidth of 3.6 MHz. It is able to detect signals with optical power as low as 10 nW and produces a minimum signal‐to‐noise ratio (SNR) of 24 dB regardless of gain configuration. The detector has been proven to be able to effectively select and combine signals from different pixels. The key advantages of this detector are smaller dimensions, higher cost effectiveness, lower voltage and power requirements and better integration. The photon detector supports pixel‐selection configurability which may improve overall SNR and also potentially generate images for different analyses. This work has contributed to the future research of system‐level integration of a pixellated solid‐state detector for secondary electron detection in the scanning electron microscope. Microsc. Res. Tech. 76:648–652, 2013. © 2013 Wiley Periodicals, Inc. 相似文献
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Dale E. Newbury 《Scanning》1996,18(7):474-482
The gaseous secondary electron detector (GSED) in the environmental scanning electron microscope (ESEM) permits collection of electron signals from deep inside blind holes in both conducting and insulating materials. The placement of the GSED as the final pressure-limiting aperture of the ESEM creates a situation of apparent illumination along the line of sight of the observer. In principle, any point struck by the primary beam can be imaged. Image quality depends on the depth of the hole. In brass, features at the bottom of a 1.5 mm diameter hole that was 8 mm deep were successfully imaged. 相似文献
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P. ZHANG 《Journal of microscopy》2020,277(1):23-31
Line-scan profile is always broadened due to the probe shape of the primary electron (PE) beam in scanning electron microscopy (SEM), which leads to an inaccurate dimension metrology. Currently, the effective electron beam shape (EEBS) is suggested as the broadening function to overcome this issue for theoretical analysis, rather than the widely used Gaussian profile. However, EEBS is almost impossible to be acquired due to it strongly depends on both the sample topography and the electron beam focusing condition, which makes it is impossible to be applied in practical analysis. Taking the case of gate linewidth measurement, an approach is proposed to find a best-fit traditional Gaussian profile, which can optimally replace the EEBS in the case of the same sample structure and experimental condition for construction of a database of the parameter in traditional Gaussian profile. This approach is based on the use of the ideal and broadened line-scan profiles which are both obtained from Monte Carlo (MC) simulation, but respectively by an ideal and a focusing incident electron beam model. The expected value of parameter can be obtained through deconvoluting (here using a maximum-entropy algorithm) the broadened line-scan profile then fitting it to the ideal profile. Experimenters can benefit from this database to obtain true line-scan profiles for accurate gate linewidth measurement. This work should prove useful for samples of other structures and be an extension of the database in the future. 相似文献
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PETR WANDROL 《Journal of microscopy》2007,227(1):24-29
The new scintillation detector of backscattered electrons that is capable of working at primary beam energy as low as 0.5 keV is introduced. Low energy backscattered electrons are accelerated in order to generate a sufficient number of photons. Secondary electrons are deflected back by the energy filter so that the true compositional contrast of the specimen is obtained. The theoretical models of the detector function are described and first demonstration images are presented. 相似文献
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One of the well-proven and efficient methods of obtaining a very low-energy impact of primary electrons in the scanning electron microscope is to introduce a retarding field element below the pole piece of the objective lens (OL). It is advantageous to use the specimen alone as the negatively biased electrode (i.e., cathode of the cathode lens). The optical power of the cathode lens modifies some of the standard parameters of the image formation such as relation of working distance to OL excitation or magnification to the scanning coils current, the impact angle of primary electrons, and so forth. In computer-controlled electron microscopes these parameters, particularly with regard to focusing and magnification, can be corrected automatically. Derivation of algorithms for such corrections and their experimental verifications are presented in this paper. Furthermore, a more accurate analytical expression for the focal length of an aperture lens is derived. 相似文献
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随着高集成、大功率和大口径雷达的发展,雷达结构精度对雷达低副瓣电平、测角精度等影响日趋明显。为提高结构精度指标分配的科学合理性,需梳理结构精度指标与电讯指标的对应关系,并详细分析各结构精度对应的影响因素,使雷达结构精度既能满足使用要求,又能降低实现成本。文中结合雷达结构中与电讯高度关联的阵面表面精度、天线座轴系精度、阵面位置精度和标校精度,逐个分析了各误差影响因素对结构精度的影响,并结合典型雷达给出具体分配方案,形成天线系统结构影响测角精度的定量计算方法。根据分析结果给出了结构精度测量与标定的技术实例,为类似雷达结构精度设计与测量提供借鉴。 相似文献
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A. T. Marshall 《Microscopy research and technique》1988,9(1):57-64
The analysis of bulk frozen-hydrated biological samples has developed now to a level where practical application of the technique is possible. Provided the sample is carefully coated with a conductive metal, the development of a space charge capable of causing a significant distortion of the electron diffusion volume does not seem to occur, and analytical resolution can be conveniently held to approximately 2 μm (both depth and lateral resolution). Two valid quantitative methods are available, and two methods of determining dry weight fractions are also available. An area where further research could lead to improvement in analysis of frozen-hydrated bulk samples is in the investigation of fracturing methods. If fracture planes that were flat and reproducible could be easily obtained, some of the difficulties of analysing frozen-hydrated bulk samples would be considerably reduced. 相似文献
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An exponential contrast stretching (ECS) technique is developed to reduce the charging effects on scanning electron microscope images. Compared to some of the conventional histogram equalization methods, such as bi‐histogram equalization and recursive mean‐separate histogram equalization, the proposed ECS method yields better image compensation. Diode sample chips with insulating and conductive surfaces are used as test samples to evaluate the efficiency of the developed algorithm. The algorithm is implemented in software with a frame grabber card, forming the front‐end video capture element. 相似文献
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Here we demonstrate the effects of electron–ion recombination on imaging signals utilized in low vacuum scanning electron microscopes (SEMs). The presented results show that, under normal operating conditions, recombination of ionized gas molecules with secondary electrons (SEs) suppresses a significant fraction of emitted electrons. If the ion flux (and hence the spatial dependence of the SE–ion recombination rate) is laterally inhomogeneous across the imaged region of a specimen, contrast in SE images can be influenced and in some cases (under conditions of high detector field strength and long ionic mean free path) dominated by variations in the recombination rate. Consequently, SE images of features such as topographic asperities can exhibit edge‐darkening, leading to inversion of some topographic contrast. Recognition of the extent and nature of electron–ion recombination is required for a correct understanding of processes occurring in variable pressure SEMs and, subsequently, for models of image formation. 相似文献
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Petr Schauer Ond&#x;ej Lalinský Miroslav Ku
era 《Microscopy research and technique》2019,82(3):272-282
The performance of a scintillation electron detector for a scanning electron microscope and/or a scanning transmission electron microscope (S(T)EM) based on new epitaxial garnet film scintillators was explored. The LuGAGG:Ce and LuGAGG:Ce,Mg film scintillators with chemical formula (Ce0.01Lu0.27Gd0.74)3–wMgw(Ga2.48Al2.46)O12 were prepared and their cathodoluminescence (CL) and optical properties were studied and compared with the properties of current standard bulk single crystal YAG:Ce and YAP:Ce scintillators. More specifically, CL decay characteristics, CL emission spectra, CL intensities, optical absorption coefficients, and the refractive indices of the mentioned scintillators were measured. Furthermore, electron interaction volumes with absorbed energy distributions, photomultiplier (PMT) photocathode matchings, modulation transfer functions (MTF), and the photon transport efficiencies of scintillation detectors with the mentioned scintillators were calculated. A CL decay time for the LuGAGG:Ce,Mg film scintillator as low as 28 ns with an afterglow of only 0.02% at 1 μs after the e‐beam excitation was observed. As determined from calculated MTFs, the scintillation detectors with the new film scintillators lose contrast transfer ability above 0.6 lp/pixel, while the currently commonly used YAG:Ce single crystal scintillators already do so above 0.1 lp/pixel. It was also calculated that the new studied film scintillators have an 8% higher photon transfer efficiency, even for a simple disk shape compared with the standard bulk single crystal YAG:Ce scintillator. The studied LuGAGG:Ce,Mg epitaxial garnet film scintillators were evaluated as prospective fast scintillators for electron detectors, not only in S(T)EM but also in other e‐beam devices. 相似文献
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A measurement technique for incident electron current in secondary electron (SE) detectors, especially the Everhart-Thornley (ET) detector, based on signal-to-noise ratio (SNR), which uses the histogram of a digital scanning electron microscope (SEM) image, is described. In this technique, primary electrons are directly incident on the ET detector. This technique for measuring the correlation between incident electron current and SNR is applicable to the other SE detectors. This correlation was applied to estimate the efficiency of the ET detector itself, to evaluate SEM image quality, and to measure the geometric SE collection efficiency and the SE yield. It was found that the geometric SE collection efficiency at each of the upper and lower detectors of a Hitachi S-4500 SEM was greater than 0.78 at all working distances. 相似文献