Articoli di riviste: "Field emission gun (FEG)"

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Joy, David C. "Microanalysis with a 200keV FEG TEM". Proceedings, annual meeting, Electron Microscopy Society of America 49 (agosto 1991): 700–701. http://dx.doi.org/10.1017/s0424820100087811.

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Introduction The Hitachi HF-2000 is a 200keV cold field emitter TEM, designed to offer both high resolution imaging performance and a nanometer probe-forming mode for microanalytical operation. The purpose of this paper is to report some initial microanalytical results obtained from the HF-2000 installed at the University of Tennessee.General Electron-Optical Parameters The cold field emission gun, which runs at about 5x10-9pA pressure, uses an electrostatic lens configuration and a six stage accelerator. The entire electron gun system is under the control of a dedicated microprocessor which permits all of the operational parameters of the gun to be set, monitored, and adjusted through a keyboard and display. The tip emission current can be adjusted up to 40μA, and the gun voltage ratio (that is the ratio between the voltage on the second anode and the tip extraction voltage) can be varied from 4.5 to 7.5, permitting a significant degree of flexibility in optimizing the optics of the emitter.

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Brock, Judith M., Max T. Otten e Marc J. C. de Jong. "Performance and applications of a field-emission gun TEM/STEM". Proceedings, annual meeting, Electron Microscopy Society of America 50, n. 2 (agosto 1992): 942–43. http://dx.doi.org/10.1017/s0424820100129346.

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A Field Emission Gun (FEG) on a TEM/STEM instrument provides a major improvement in performance relative to one equipped with a LaB6 emitter. The improvement is particularly notable for small-probe techniques: EDX and EELS microanalysis, convergent beam diffraction and scanning. The high brightness of the FEG (108 to 109 A/cm2srad), compared with that of LaB6 (∼106), makes it possible to achieve high probe currents (∼1 nA) in probes of about 1 nm, whilst the currents for similar probes with LaB6 are about 100 to 500x lower. Accordingly the small, high-intensity FEG probes make it possible, e.g., to analyse precipitates and monolayer amounts of segregation on grain boundaries in metals or ceramics (Fig. 1); obtain high-quality convergent beam patterns from heavily dislocated materials; reliably detect 1 nm immuno-gold labels in biological specimens; and perform EDX mapping at nm-scale resolution even in difficult specimens like biological tissue.The high brightness and small energy spread of the FEG also bring an advantage in high-resolution imaging by significantly improving both spatial and temporal coherence.

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Tomita, T., S. Katoh, H. Kitajima, Y. Kokubo e Y. Ishida. "Development of Field-Emission Gun for High-Voltage Electron Microscope". Proceedings, annual meeting, Electron Microscopy Society of America 48, n. 2 (12 agosto 1990): 94–95. http://dx.doi.org/10.1017/s0424820100134065.

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It is well known that the combination of a field emission gun (FEG) and a conventional transmission electron microscope (CTEM) is extremely important for nanometer area analysis in analytical electron microscopy. However, the smaller illumination angle and reduced energy spread of FEG than those of a conventional electron gun (W hair pin filament or LaB6) give a slowly damping envelop function in phase contrast transfer function (PCTF). Thus the FEG ensures application not only to analytical microscopy but also to high resolution electron microscopy to improve the information limit.In a high voltage electron microscope (above 200 kV), high-speed vacuum pumps have to be provided below the acceleration tube to get an ultra high vacuum (UHV) around the field emission tip located at the top of the acceleration tube. However, this method is not always the best way to provide UHV because of the poor vacuum conductance caused by the electrodes inside the acceleration tube.

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Mul, P. M., B. J. M. Bormans e L. Schaap. "Design of a Field-Emission Gun for the Phillips CM20/STEM microscope". Proceedings, annual meeting, Electron Microscopy Society of America 48, n. 2 (12 agosto 1990): 100–101. http://dx.doi.org/10.1017/s0424820100134090.

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The first Field Emission Guns (FEG) on TEM/STEM instruments were introduced by Philips in 1977. In the past decade these EM400-series microscopes have been very successful, especially in analytical electron microscopy, where the high currents in small probes are particularly suitable. In High Resolution Electron Holography, the high coherence of the FEG has made it possible to approach atomic resolution.Most of these TEM/STEM systems are based on a cold field emitter (CFE). There are, however, a number of disadvantages to CFE’s, because of their very small emission region: the maximum current is limited (a strong disadvantage for high-resolution TEM imaging) and the emission is unstable, requiring special measures to reduce the strong FEG-induced noise. Thermal field emitters (TFE), i.e. a zirconiated field emitter source operating in the thermal or Schottky mode, have been shown to be a viable and attractive alternative to CFE’s. TFE’s have larger emission regions, providing much higher maximum currents, better stability, and reduced sensitivity to vacuum conditions as well as mechanical and electrical interferences.

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Murakoshi, H., M. Ichihashi, T. Komoda, S. Isakozawa e T. Kubo. "Field-emission gun and illuminating lens system for 200kV FE-TEM". Proceedings, annual meeting, Electron Microscopy Society of America 47 (6 agosto 1989): 110–11. http://dx.doi.org/10.1017/s0424820100152525.

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Good resolution is obtained with a conventional transmission electron microscope (TEM). Nevertheles, an atomic scale analysis is difficult because of insufficient probe current. A field emission gun (FEG) provides a higher brightness and more monochromatic beam than a thermionic one. Thus, an FEG can be expected to improve the abilities of a TEM. The low energy spread(∼0.5 eV) attainable with the FEG reduces chromatic aberrations and a brighter image can be expected, making more discernible details. In addition, a high beam current is formed in a small spot, enabling precise element analysis at the nanometer level. Moreover, the illuminating angle obtained on a specimen is so small that electron diffraction can be clearly obtained for structure analysis of crystals. Experimental FE-TEMs with lower accelerating voltage than 100kV have already been developed. Using an electron holography technique, micro magnetic flux was observed with a high coherency beam. FE-TEMs with a higher accelerating voltage are required in various fields of material science.

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Olson, N. H., U. Lücken, S. B. Walker, M. T. Otten e T. S. Baker. "Cryoelectron microscopy and image reconstruction of spherical viruses with spot scan and FEG technologies". Proceedings, annual meeting, Electron Microscopy Society of America 53 (13 agosto 1995): 1086–87. http://dx.doi.org/10.1017/s0424820100141809.

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The field emission gun electron microscope (FEG) is a tool that has the potential to achieve near atomic resolution information of biological macromolecules. The FEG provides a beam with higher spatial and temporal coherence and a better phase contrast transfer function than do microscopes with either tungsten or LaB6 filaments. The FEG is also ideal for spot scan imaging applications because it can produce a small, coherent and very bright spot. In spot scan mode the specimen is exposed to an array of nonoverlapping spots rather man a flood beam. This significantly reduces beam-induced specimen drift.Frozen-hydrated samples of cowpea chlorotic mottle (CCMV, Fig. 1A) and cowpea severe mosaic virus (CPSMV, Fig. IB) were examined on a Philips CM12 transmission electron microscope equipped with a standard LaB6 gun and on a Philips CM200 equipped with a field emission gun, respectively. The CM12 was operated at 120kV and was externally controlled by means of a spot scan imaging program which produced a series of 250 nm diameter spots on Kodak SO-163 sheet film.

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Ohi, M., K. Harasawa, T. Niikura, H. Okazaki, Y. Ishimori, T. Miyokawa e S. Nakagawa. "Development of a New Digital Fe SEM". Proceedings, annual meeting, Electron Microscopy Society of America 48, n. 1 (12 agosto 1990): 432–33. http://dx.doi.org/10.1017/s0424820100180914.

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By combining a conical type field emission gun and an auto gain controlled noise cancelling system, we have developed three types of digital FESEMs equipped with a digital imaging processor and three different sized specimen chambers each with a stage.It is known that when a cold field emission gun (C-FEG) with a W (310) single crystal tip is used at a vacuum pressure of 10-10 torr, the emission current constantly fluctuates by 5 to 10% due to the adsorbed gas, etc. on the tip surface.Since the probe current in an FESEM equipped with this C-FEG fluctuates to the same extent, the noise caused by emission current fluctuation (emission noise) appears on secondary electron images (SEI) and backscattered electron images (BEI).In order to eliminate emission noise, an aperture (noise cancelling aperture or N/C aperture) installed under the C-FEG detects emission current fluctuation and inputs it to the differential amplifier of the video amplifier system for SEI or BEI on conventional FESEMs.With FESEMs, however, when the accelerating voltage is change in the range from 0.5 to 30 kV, the virtual source of an FEG using Butler type electrodes moves several tens of centimeters on the optical axis. Moreover, the probe current is changed from 10-13 to 10-10 A by changing the excitation current of the condenser lens. For these two reasons, there have been adopted such methods as installing an N/C aperture in two positions (under the C-FEG and at the objective lens aperture position) and controlling the amplifier value of the noise cancelling system and condenser lens excitation by ROM data.

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Troyon, Michel, e He Ning Lei. "Electron Trajectories Calculations of an Energy - Filtering Field-Emission Gun". Proceedings, annual meeting, Electron Microscopy Society of America 48, n. 1 (12 agosto 1990): 192–93. http://dx.doi.org/10.1017/s0424820100179713.

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In many cases, the contribution of beam energy spread to the limitation of the performances of an electron microscope is strong. In the case of the field emission gun (FEG) , Troyon has experimentally shown it is possible to reduce considerably the energy spread by energy filtering at the gun level. The system developed consists basically of a magnetic FEG with a retarding electrode working as the retarding electrode of an energy filter. The principle is recalled in Fig. 1 and the cross section of the accelerator is given in Fig. 2. In this paper, the results of electron trajectories calculations inside the energy filtering field emission gun (EFFEG) are given.Fig. 3 shows that electrons of same energy, but entering the retarding field with different angles, can have exit angles very different. Due to the work function of approximately 4.5 eV the electrons, for an extracting potential Vo = 2 kV, enter in the field of the retarding electrode with an energy smaller than 2 keV. In Fig. 3 trajectories are computed for an electron of 1996 eV. Electrons passing by the nodal points have the same entering and exit angles. Trajectory 1 in Fig. 3 corresponds to an entering radius re = 17.5 μm and an entering semi angle αe = 1.2 mrad. For these re and αe values, at Vr =6 V, the exit semi angle αs = αe . Fig. 3 shows that an electron entering parallely to the axis, even very close to the axis (re = 10 μm) has a larger exit angle than electrons passing by the nodal points.

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Kaneyama, T., M. Kawasaki, T. Tomita, T. Honda e M. Kersker. "The information limit of a 200kv field emission TEM". Proceedings, annual meeting, Electron Microscopy Society of America 53 (13 agosto 1995): 586–87. http://dx.doi.org/10.1017/s0424820100139305.

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The Point resolution of a transmission electron microscope is normally defined by the reciprocal of the spatial frequency of the first zero in the phase contrast transfer function at the Scherzer defocus condition. When a field emission gun (FEG) is used as the electron source, the information limit, that point at which the contrast beyond the first zero goes to zero contrast, becomes equally important. We have investigated the primary microscope parameters that affect the information limit.A 200kV FE-TEM (JEM-2010F) equipped with a ZrO/W shottkey emitter and Gatan Parallel EELS (PEELS) was used for the experiments. The aberration coefficients of the objective lens are Cs = 1mm and Cc = 1.4mm. The specimen used is an evaporated amorphous Ge thin film with small gold islands.The resolution performance of the microscope depends not only on the performance of the objective lens, the high voltage stability, stability of the lens and deflector power supplies, operating parameters of the FEG, and the overall mechanical stability of the microscopes.

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Coened, W. M. J., A. J. E. M. Janssend, M. Op de Beeck, D. Van Dyck, E. J. Van Zwet e H. W. Zandbergen. "Focus-variation image reconstruction in field-emission TEM". Proceedings, annual meeting, Electron Microscopy Society of America 51 (1 agosto 1993): 1070–71. http://dx.doi.org/10.1017/s0424820100151180.

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The use of a field emission gun (FEG) in high resolution TEM (HRTEM) improves the information limit much below the point resolution. This is due to the FEG’s high brightness and low energy spread which yield a very good coherence. In the area between point and information resolution of the FEG-TEM, image interpretation is complicated by the lens aberrations and focus effects, which cause scrambling of the information from the specimen. This problem is solved by ‘holographic’ techniques, which retrieve aberration-corrected amplitude and phase information of the electron wave ϕ at the exit plane of the specimen. We follow the route of ‘in-column’ or ‘nonlinear’ holography by digital processing of a focal series of HRTEM images. Different reconstruction algorithms can be used for that purpose depending on the assumptions that are made in the HRTEM imaging model. We have devised two workable algorithms. A first method, called the “paraboloid method” (PAM), aims at filtering out recursively the nonlinear contributions in the images, so that high-speed linear reconstruction can be applied.

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Neves, F., A. Cunha, I. Martins, J. B. Correia, M. Oliveira e E. Gaffet. "Ni4Ti3 Precipitation during Ageing of MARES NiTi Shape Memory Alloys Studied by FEG-SEM". Microscopy and Microanalysis 14, S3 (settembre 2008): 13–16. http://dx.doi.org/10.1017/s1431927608089241.

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The use of a high-brightness field-emission gun (FEG) in scanning electron microscopy (SEM) is a powerful technique to examine microstructures at very high spatial resolution down to nanometer level and has significantly enhanced our ability to solve challenging materials problems, allowing studies of nanoprecipitates.

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Hombourger, C., e M. Outrequin. "Quantitative Analysis and High-Resolution X-ray Mapping with a Field Emission Electron Microprobe". Microscopy Today 21, n. 3 (maggio 2013): 10–15. http://dx.doi.org/10.1017/s1551929513000515.

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The electron probe microanalyzer (EPMA) provides quantitative analysis for nearly all chemical elements with a spatial resolution of analysis about ~1 μm, which is relevant to microstructures in a wide variety of materials and mineral specimens. Recent implementation of the Schottky emitter field-emission gun (FEG) electron source in the EPMA has significantly improved the spatial resolution and detectability of the EPMA technique.

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Otten, Max T., e Wim M. J. Coene. "Principle and practice of high-resolution imaging with a field-emission TEM". Proceedings, annual meeting, Electron Microscopy Society of America 50, n. 1 (agosto 1992): 138–39. http://dx.doi.org/10.1017/s0424820100121090.

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High-resolution imaging with a LaB6 instrument is limited by the spatial and temporal coherence, with little contrast remaining beyond the point resolution. A Field Emission Gun (FEG) reduces the incidence angle by a factor 5 to 10 and the energy spread by 2 to 3. Since the incidence angle is the dominant limitation for LaB6 the FEG provides a major improvement in contrast transfer, reducing the information limit to roughly one half of the point resolution. The strong improvement, predicted from high-resolution theory, can be seen readily in diffractograms (Fig. 1) and high-resolution images (Fig. 2). Even if the information in the image is limited deliberately to the point resolution by using an objective aperture, the improved contrast transfer close to the point resolution (Fig. 1) is already worthwhile.

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Garratt-Reed, Anthony J., e Sebastian von Harrach. "Early experience with a 300kV FEG STEM". Proceedings, annual meeting, Electron Microscopy Society of America 49 (agosto 1991): 348–49. http://dx.doi.org/10.1017/s0424820100086040.

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At the time of writing, a model VG HB603 300kV analytical scanning transmission electron microscope with a field-emission gun (FEG-STEM) is undergoing its final evaluation for acceptance at MIT. The instrument as supplied has an electrostatic gun lens, two magnetic condenser lenses, a symmetric objective lens with a spherical aberration coefficient of 4.5mm., and three post-specimen lenses intended for minimizing distortion of the diffraction patterns while changing camera length. The specimen holder is of the side-entry type, with “z-adjustment” (i.e. control of the specimen position along the microscope axis). For single-tilt applications a holder accepting three specimens simultaneously is provided, which, together with the double-tilt holder, has all parts near the sample made of beryllium. The point-to-point resolution in the image is computed to be 0.28nm. X-axis tilt is +/-600, and, in the double-tilt holder, Y-axis tilt is +/-45°.

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Cui, Wen, e Shao Jun Qi. "The Effect of Surface Finish on Zinc Whisker Growth". Advanced Materials Research 472-475 (febbraio 2012): 2756–59. http://dx.doi.org/10.4028/www.scientific.net/amr.472-475.2756.

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To understand the relationship between surface finish and zinc whisker growth, this study investigated the growth of whiskers on two mild steel substrates of different surface finish by Field Emission Gun Scanning Electron Microscope (FEG SEM). Results show that, under the same experimental conditions, deposits on substrates with a mirror finish grew less whiskers and nodules than substrates with a rough surface finish.

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Krivanek, Ondrej L., James H. Paterson e Helmut R. Poppa. "Performance of the Gatan PEELS™ on the VG HB501 STEM". Proceedings, annual meeting, Electron Microscopy Society of America 47 (6 agosto 1989): 410–11. http://dx.doi.org/10.1017/s0424820100154020.

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Parallel-detection electron energy-loss spectrometers offer several hundred times the detection efficiency of serial-detection spectrometers, as well as improved energy resolution. These advantages should be especially important when using a scanning transmission electron microscope (STEM) with a cold field emission gun (FEG), in which the available beam current is typically 10 to 100 times less than in a conventional TEM, while the beam energy spread is typically only 0.3 eV. We have therefore investigated the performance of the Gatan parallel-detection spectrometer (Gatan model 666 PEELS™) when mounted on the VG HB501 FEG STEM.

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Veiss, J. K., e R. W. Carpenter. "A study of small probe formation in a field emission gun TEM/STEM". Proceedings, annual meeting, Electron Microscopy Society of America 46 (1988): 510–11. http://dx.doi.org/10.1017/s0424820100104613.

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A Philips EM 400T equipped with a field emission gun (FEG) has been studied to determine the spatial and angular current distribution in the electron microprobe at the specimen level. The field emission gun provides a high brightness source capable of producing electron probes with diameters of several nanometers and total currents of 0.05 - 50 nA. The advantage of the TEM/STEM over the dedicated STEM in this study is its ability to produce real-space images of the probe at the specimen plane. Detailed information about the probe current distribution can be experimentally obtained and applied to various small-probe techniques (i.e. HRAEM, STEM, microdiffraction) in order to determine their spatial resolution.The probe diameters listed in Table 1 were measured from high magnification images of the focussed probes which showed sharply defined outlines of the aberration figures. Additional measurements were obtained by scanning the probe across a small fixed entrance aperture to an EELS spectrometer, and also by an edge resolution method similar to that used by Venables and Janssen.

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Coene, W., A. F. de Jong, H. Lichte, M. Op de Beeck, H. Tietz e D. Van Dyck. "FEG - TEM: The route to HREM". Proceedings, annual meeting, Electron Microscopy Society of America 50, n. 1 (agosto 1992): 100–101. http://dx.doi.org/10.1017/s0424820100120904.

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Several technological improvements in TEM have nowadays been realized which offer possibilities for ultra-high resolution electron microscopy at intermediate voltages. These improvements include new objective lens polepieces, field emission gun (FEG) TEMs and slow-scan CCD camera's. A project has been initiated for the period 1990-1994, for the development of ultra-HREM, which combines know-how both from industry (Philips, Tietz) and university (Antwerp, Tübingen, Delft, Arizona). The project is partly sponsored by the European Community (Brite-Euram program nr. 3322). The goal of the project is to achieve 0.1 nm structural resolution by using the information limit rather than the point resolution of the instrument. The information limit is extended towards the 0.1 nm range (at 300 kV) by the much better spatial and temporal coherence of the FEG as compared with LaB6 sources.

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Ishikawa, I., K. Kaneyama, T. Tomita, T. Honda e M. Kersker. "Information limit of a 300kV field emission TEM". Proceedings, annual meeting, Electron Microscopy Society of America 53 (13 agosto 1995): 588–89. http://dx.doi.org/10.1017/s0424820100139317.

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The use of an FEG on a high resolution microscope will increases the spacial and temporal coherence of the microscope due to the improvement in coherence of the electron source. Additionally, the improved energy spread will extend the envelope of the phase contrast transfer well beyond the first zero point at Sherzer focus. Between the Sherzer point and the ultimate point of zero contrast (the information limit) there is useful information for the analysis of high-resolution images. We have already obtained a resolution of 0.194nm and an information limit of 0.14nm by using the 200kV FETEM (JEM-2010F). In the present experiment, we attempted to obtain a higher resolution and information limit by using the 300kV FE TEM (JEM-3000F).The electron gun is configured with a ZrO/W Shottky emitter which has a small energy spread with a stable emission. The objective lens has a spherical and chromatic aberration of 0.6mm and 1.3mm respectively. The specimen used was gold islands on an amorphous Ge thin film.

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Harada, Ken, Haruto Nagata, Ryuichi Shimizu, Takayoshi Tanji e Keiji Yada. "<310> Single-Crystal LaB6 as Thermal Field Emitter for Electron Microscope". Proceedings, annual meeting, Electron Microscopy Society of America 48, n. 1 (12 agosto 1990): 196–97. http://dx.doi.org/10.1017/s0424820100179737.

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Thermal field emission (T.F.E.) properties of single crystal LaB6 -tips has been investigated by observing emission patterns. Applying field evaporation technique we succeeded to get the clean pattern consisting of <310> spots with very good reproducibility. This investigation has led to conclusion;, the <310> spot is promising electron source of high brightness provided that the tip is operated at tip temperature∽ 1000-1050°C in vacuum of 10−9 Torr region.As a preliminary experiment of brightness-measurement, we mounted the <310> LaB6-tip in a commercial type TEM, JEM-100CX-FEG, attached with an electron gun system for T.F.E. of <100> W-tip, being operated at 10−9 Torr region without Schottky shield electrode. The LaB6-tip, however, can not be operated without the Schottky shield because thermionic emission (T.E.) from the LaB6-tip is considerably high even though the tip is operated at lower than ∽1000 °C. In the present experiment, therefore, we manufactured a Schottky shield electrode as shown in Fig.l and performed the measurement of brightness by setting the Schottky shield electrode, applied the same voltage as the tip since the electron gun system has no extra feed-throughs for bias-voltage.

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Xavier, Camila Soares, Ana Paula de Moura, Elson Longo, José Arana Varela e Maria Aparecida Zaghete. "Synthesis and Optical Property of MgMoO₄ Crystals". Advanced Materials Research 975 (luglio 2014): 243–47. http://dx.doi.org/10.4028/www.scientific.net/amr.975.243.

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In this work, we report on the synthesis of MgMoO4 crystals by oxide mixed method. The powder was calcined at 1100 °C for 4h and analyzed by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Field emission gun scanning electron microscopy (FEG-SEM), Ultraviolet-visible (UV-vis) absorption spectroscopy and Photoluminescence (PL) measurement. XRD analyses revealed that the MgMoO4 powders crystallize in a monoclinic structure and are free secondary phases. UVvis technique was employed to determine the optical band gap of this material. MgMoO4 crystals exhibit an intense PL emission at room temperature with maximum peak at 579 nm (yellow region) when excited by 350 nm wavelength at room temperature.

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Howe, J. M., S. P. Ringer, B. C. Muddle e I. J. Polmear. "Analytical Electron Microscopy of nanometer-size precipitates in al alloys with a 200-kV field-emission TEM". Proceedings, annual meeting, Electron Microscopy Society of America 54 (11 agosto 1996): 574–75. http://dx.doi.org/10.1017/s0424820100165331.

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Certain trace elements are known to have a pronounced effect on the nucleation kinetics of metastable phases in Al alloys. This provides many opportunities for alloy design. Understanding the role of trace elements in the precipitation process is difficult because they are typically present at levels of less than 0.1 at.% and involve early stages of clustering or segregation to precipitates. This paper presents recent results from the application of a 200 kV thermal field-emission gun (FEG) transmission electron microscope (TEM) to study trace element additions and the early stages of precipitation in Al alloys, using the case of an experimental alloy designated ALMAGEM as an example.An Al-2.41Cu-0.34Mg-0.lSi-0.04Ge alloy was cast into a book mold, homogenized, solution treated at 525°C, water quenched and aged for 12.5 h at 170°C to peak hardness. Disks 3 mm in diameter were electropolished in a HNOs/methanol solution and examined at 200 kV in a JEOL 2010F FEG TEM with a high-tilt (±30°) pole piece.

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Sun, H. P., H. Li, H. D. Li, G. T. Zou, Z. Zhang e X. Q. Pan. "Electron Beam Irradiation Induced Structural Modulation and Damage in GaN Nano Crystals". Microscopy and Microanalysis 7, S2 (agosto 2001): 492–93. http://dx.doi.org/10.1017/s1431927600028531.

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GaN is a semiconductor material with promising applications in display and laser devices. GaNbased thin films have been grown by various methods and intensively investigated. Additionally, GaN nano particles have been prepared by various different methods. in this paper, we report our new finding of the structural modulation of GaN nano crystals induced by electron beam irradiation within a transmission electron microscope (TEM). The origin of the modulation structure is due to the ordering of N vacancies in the GaN nano crystals.The GaN nano crystals were prepared by d.c arc plasma method. A Philips CM200 TEM with a field emission gun (FEG) operating at 200KV was used in this study. The GaN nano crystals normally show hexagonal shape (see Fig.la). Corresponding electron diffraction pattern along [0001] axis indicates the Wurtzite structure (see Fig. lb). It was unexpected that satellite reflections gradually appeared in the diffraction pattern after the GaN nano crystal had been exposed to the electron beam (see Fig.lc-d).

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Stark, H., E. Beckmann, R. Henderson e F. Zemlin. "SOPHIE, a helium cooled superconducting Electron Microscope with a Schottky field emitter". Proceedings, annual meeting, Electron Microscopy Society of America 53 (13 agosto 1995): 72–73. http://dx.doi.org/10.1017/s0424820100136738.

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High-resolution cryo-electron microscopy yielded remarkable results in biological molecular structure research. These successes encouraged to proceed in developing even better instruments and procedures. In our laboratory we built the cryo-electron microscope "SOPHIE", a modified Philips CM 20 FEG. SOPHIE stands as an acronym for Superconducting Objective in a PHIlips Electronmicroscope. The main features of this microscope are the following: 1.200kV acceleration voltage2.Schottky field emitter3.Helium cooled superconducting objective The Helium-cooled cryo-objective from the former microscope SULEIKA was adapted into the column of the original Philips CM20 FEG [Fig. 1], This new SOPHIE microscope, thus, combines two important features: a modern computer controlled electron microscope with a high coherent beam source and the proven advantages of the superconducting cryo-objective. The advantage of the field emission gun at 200 kV over a thermionic cathode at 100 kV can be best visualized while comparing the respective phase-contrast-transfer functions at Scherzer focus [Fig.2]. Moreover, SOPHIE is equipped with the small spot scanning procedure.

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Navarro da Rocha, Daniel, Leila Rosa de Oliveira Cruz, João Luiz do Prado Neto, Nadia Mohammed Elmassalami Ayad, Luciano de Andrade Gobbo e Marcelo Henrique Prado da Silva. "Production and Characterization of Hydroxyapatite/Niobo Phosphate Glass Scaffold". Key Engineering Materials 587 (novembre 2013): 128–31. http://dx.doi.org/10.4028/www.scientific.net/kem.587.128.

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The present study concerns the production and characterization of porous hydroxyapatite/niobo-phosphate glass ceramics to be used for bone repair. The scaffolds were produced by hydrothermal deposition of monetite on polyurethane sponge substrates, further converted to hydroxyapatite in an alkali solution. After heat treatment, elimination of the organic sponge provides a three-dimensional (3D) structure. Niobo-phosphate glasses were added to the heat treated struts and the scaffolds were sintered. The porous bodies were characterized by field-emission gun scanning electron microscope (FEG-SEM) with energy-dispersive X-ray spectroscopy (EDS).

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26

Watanabe, M., D. W. Ackland, A. Burrows, C. J. Kiely, D. B. Williams, O. L. Krivanek, N. Dellby, M. F. Murfitt e Z. Szilagyi. "Improvements in the X-Ray Analytical Capabilities of a Scanning Transmission Electron Microscope by Spherical-Aberration Correction". Microscopy and Microanalysis 12, n. 6 (11 ottobre 2006): 515–26. http://dx.doi.org/10.1017/s1431927606060703.

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A Nion spherical-aberration (Cs) corrector was recently installed on Lehigh University's 300-keV cold field-emission gun (FEG) Vacuum Generators HB 603 dedicated scanning transmission electron microscope (STEM), optimized for X-ray analysis of thin specimens. In this article, the impact of the Cs-corrector on X-ray analysis is theoretically evaluated, in terms of expected improvements in spatial resolution and analytical sensitivity, and the calculations are compared with initial experimental results. Finally, the possibilities of atomic-column X-ray analysis in a Cs-corrected STEM are discussed.

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27

Ohye, Toshimi, Yoshiki Uchikawa, Chiaki Morita e Hiroshi Shimoyama. "Aberrations of Accelerating Tube for High-Voltage Electron Microscope". Proceedings, annual meeting, Electron Microscopy Society of America 48, n. 1 (12 agosto 1990): 194–95. http://dx.doi.org/10.1017/s0424820100179725.

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The accelerating tube (AT) which accelerates electrons up to a desired energy also functions as an electrostatic lens, In the present paper, numerical calculations were conducted on the electron optical characteristics including the spherical aberration of the AT for the high voltage electron microscope. Several electron optical problems arising from a combination of the AT with a thermionic electron gun (TEG) or a field emission gun (FEG) were studied.<Estimation of aberration for AT lens> The AT consists of 34 electrodes with the inner diameter of 3.3 cm and has the overall length of 142.3 cm (Fig.l). The voltage Va is applied between the cathode and the final electrode of the AT. The initial energy of the electron incident to the AT is eVo, where Vo is the anode voltage of the electron gun mounted on the AT. The electric field inside the AT was calculated using the surface charge method. The ray tracing was carried out on the basis of the relativistic paraxial ray equation, and the cardinal elements of the AT lens were obtained.

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Oikawa, T., M. Kawasaki, T. Kaneyama, Y. Ohkura e M. Naruse. "The New EF-TEM with OMEGA and FEG". Microscopy and Microanalysis 7, S2 (agosto 2001): 1128–29. http://dx.doi.org/10.1017/s1431927600031718.

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Recently, energy filtering technique in the transmission electron microscopy (EF-TEM) is becoming widely used in both materials and biological science.In this paper, newly developed EF-TEMs for both 200 kV (JEM-2010FEF) and 300 kV (JEM- 3100FEF) are introduced. Figure 1 shows appearances of the instruments. Those instruments have a field emission gun and an OMEGA type spectrometer.The features of JEM-2010FEF and JEM-3100FEF EF-TEMs are as follows [1,2]:1. 3 pre-filter lenses and 3 post-filter lenses are used.Additional intermediate lens is employed for covering filtered images in low magnification range from x200 - x 1,500,000 magnification for JEM-2010FEF, x200 - x2,000,000 for JEM- 3100FEF. in diffraction mode, from 200 mm - 2,000 mm in camera length for JEM- 2010F, 200 mm- 1,500 mm are covered for JEM-3100FEF.2. Large energy dispersion.The energy dispersion is 1.2 μm/eV at 200 kV and 0.85 μm/eV at 300 kV.

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29

Navarro da Rocha, Daniel, Leila Rosa de Oliveira Cruz, Luciano de Andrade Gobbo e Marcelo Henrique Prado da Silva. "Bioactivity Assessment of Niobate Apatite". Key Engineering Materials 614 (giugno 2014): 3–6. http://dx.doi.org/10.4028/www.scientific.net/kem.614.3.

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Hydroxyapatite is a bioceramic material of great interest for use as bone substitute because of its similarity with the composition of biological apatite. Cationic and anionic substitutions in the apatite structure have been made in order to optimize the synthesis and accelerate the process of bone repair. In the present study, niobate apatite was synthesized by a patented aqueous precipitation method. The bioactivity of the samples was assessed by X-ray diffraction analyses (XRD), energy dispersive X-ray spectroscopy (EDS) and scanning electron microscopy with field emission gun (FEG-SEM; FEI Quanta FEG 250) in the samples before and after an incubation period in simulated body fluid. The results showed that after 3 days a bone-like apatite coating was formed onto the niobate apatite surface. A peculiar morphology comprised by nanosized wires was also observed on the niobate apatite surface.

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30

Sandim, Hugo Ricardo Zschommler, e Dierk Raabe. "An EBSD Study on Orientation Effects during Recrystallization of Coarse-Grained Niobium". Materials Science Forum 467-470 (ottobre 2004): 519–24. http://dx.doi.org/10.4028/www.scientific.net/msf.467-470.519.

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The recrystallization behavior of coarse-grained niobium depends on the nature of its deformation microstructure. In this regard, a longitudinal section of a high-purity coarse-grained niobium ingot was cold rolled to a thickness reduction of 96% followed by annealing in vacuum at 800°C for 1 h. Metallographic inspection in cold-rolled and annealed specimens was carried out in a field emission gun scanning electron microscope (FEG-SEM). Microtexture was determined by electron-backscattered diffraction (EBSD) coupled to the FEG-SEM. The use this technique has evidenced details of the boundary character and subgrain structure found in partially recrystallized regions. The early stages of primary recrystallization are associated to the presence of high-angle lamellar boundaries found in the cold-worked state. Abnormal subgrain growth has been evidenced as a viable mechanism for nucleation of recrystallization.

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31

Vronka, Marek, e Miroslav Karlík. "Microstructure and Mechanical Properties of Al-Mn Sheets with Zr Addition". Key Engineering Materials 606 (marzo 2014): 19–22. http://dx.doi.org/10.4028/www.scientific.net/kem.606.19.

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Abstract (sommario):

The aim of the experiments was to study the influence of the rolling reduction in thickness on the size and distribution of secondary particles and recrystallization behaviour of Al-Mn sheets with Zr addition prepared by twin-roll casting (TRC) in the industrial conditions. Samples, cold rolled on a laboratory mill, were subjected to a one and two-step precipitation annealing. Their microstructure (grain structure, phase composition, particle analysis) and mechanical and physical properties (microhardness, electrical conductivity) were then characterized. Quantitative particle analysis was carried out on field-emission gun scanning electron microscope (FEG-SEM) micrographs.

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32

Toptan, F., Ayfer Kilicarslan e Isil Kerti. "The Effect of Ti Addition on the Properties of Al-B₄C Interface: A Microstructural Study". Materials Science Forum 636-637 (gennaio 2010): 192–97. http://dx.doi.org/10.4028/www.scientific.net/msf.636-637.192.

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In the present work, Al-B4C composites were produced by casting route at 850°C and titanium-containing flux was used to overcome the wetting problem between B4C and liquid aluminium metal. The microstructure of matrix/reinforcement interface was investigated using SEM studies with or without Ti added composites. The reaction layer was also characterized with EDS analysis and X-ray mapping. It was found from the microstructural observations by high resolution field emission gun SEM (FEG-SEM) that the wetting issue was effectively solved by the formation of very thin (80-180 nm in thickness) Ti-C and Ti-B reaction layers.

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33

Pezzotti, Giuseppe. "Interfacial Residual Stresses in Semiconductor Devices Measured on the Nano-Scale by Cathodoluminescence Piezospectroscopy". Solid State Phenomena 127 (settembre 2007): 123–28. http://dx.doi.org/10.4028/www.scientific.net/ssp.127.123.

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Abstract (sommario):

Electron-stimulated (cathodo)luminescence spectroscopy is quantitatively used for obtaining information about the residual stress fields piled up in semiconductor materials and devices during manufacturing. This additional micromechanical output can be added to the microscopic structural/chemical information available in the scanning electron microscope (SEM) by other conventional techniques. Independent of the physical mechanisms behind the luminescence emission, the spectral position of selected cathodoluminescence (CL) bands, observed in both crystalline and glassy materials, is shown to possess high stress sensitivity and thus suitability as a sensor for residual stress assessments. In this paper, we first quantitatively characterize the stress dependence of typical CL bands observed in ceramic and glassy semiconductor materials. Then, based on this knowledge, applications are shown of two-dimensional residual stress mapping on the nano-meter scale in electronic devices involving atomically sharp interfaces, according to an optimized automatic procedure performed into a field-emission gun (FEG-)SEM.

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34

Navarro da Rocha, Daniel, Leila Rosa de Oliveira Cruz, Dindo Q. Mijares, Rubens Lincoln Santana Blazutti Marçal, José Brant de Campos, Paulo G. Coelho e Marcelo Henrique Prado da Silva. "Bioactivity Assessment of Calcium Phosphate Coatings". Key Engineering Materials 720 (novembre 2016): 193–96. http://dx.doi.org/10.4028/www.scientific.net/kem.720.193.

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Abstract (sommario):

Nowadays, bioactive coatings or modifications on titanium surface have been tested in vitro and in vivo. In this study, two types of calcium phosphate coatings were produced by a chemical deposition method and their bioactivity assay in cell culture medium were investigated. The calcium phosphate coatings were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy with field emission gun (FEG-SEM) analyses. Titanium substrate was successfully coated with brushite using chemical deposition method and, after a second step of conversion, the hydroxyapatite coating was obtained. The hydroxyapatite coating showed a bioactivity property after 14 days’ incubation in McCoy medium culture.

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35

Nenadovic, Milos, Danilo Kisic, Miljana Mirkovic, Snezana Nenadovic e Ljiljana Kljajevic. "Structural and optical properties of HDPE implanted with medium fluences silver ions". Science of Sintering 53, n. 2 (2021): 187–98. http://dx.doi.org/10.2298/sos2102187n.

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The implantation of high-density polyethylene (HDPE) has been conducted using Ag+ ions with energy of 60 keV, achieved fluences 1.5 and 10?1015 ions/cm2. Transmission electron microscopy (STEM) and field emission gun - scanning electron microscopy (FEG-SEM) showed the existence of nanoparticle clusters. X ray photoelectron spectroscopy (XPS) revealed the presence of silver in the sample surface region. The surface topography was studied by atomic force microscopy (AFM), while the surface composition uniformity was analyzed using phase imaging AFM. Optical characterization obtained by spectroscopic ellipsometry (SE) showed changes in refractive index, extinction coefficient and the optical band gap with the fluence of implanted ions.

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36

Takeguchi, M., T. Honda, Y. Ishida, M. Kersker, M. Tanaka e K. Furuya. "Ultrahigh-Vacuum Field-Emission Electron Microscope as Applied to Observation and Analysis of Crystal Surface". Microscopy and Microanalysis 3, S2 (agosto 1997): 597–98. http://dx.doi.org/10.1017/s1431927600009879.

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UHV(ultrahigh-vacuum) TEM has long been used as a powerful tool for studying crystal surfaces, particularly for both the direct imaging of the surface structure and for in-situ observation of surface reaction processes with atomic resolution.This paper reports a newly developed 200kV UHV TEM equipped with a field emission gun(FEG). The instrument is designed to obtain information about elemental or bonding states of surfaces in addition to observation of surface atomic structure with high contrast. Basic performances of the UHV FE-TEM includes a specimen vacuum of 2.0X10-8Pa, probe size less than 1.0nm Ø with 0.5nA probe current, point-to-point resolution of 0.21 nm, and a lattice resolution of 0.10nm.A UHV Energy Dispersive X-ray Spectrometer (EDS) originally developed by JEOL Ltd. and a Parallel Electron Energy Loss Spectrometer (PEELS) are attached to the UHV FE-TEM, which combined with a fine focused probe of 1.Onm Ø allows atomic scale spectroscopy of surfaces.

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37

Krause, S. J., W. W. Adams, S. Kumar, T. Reilly e T. Suziki. "Low-voltage, high-resolution scanning electron microscopy of polymers". Proceedings, annual meeting, Electron Microscopy Society of America 45 (agosto 1987): 466–67. http://dx.doi.org/10.1017/s0424820100127037.

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Abstract (sommario):

Scanning electron microscopy (SEM) of polymers at routine operating voltages of 15 to 25 keV can lead to beam damage and sample image distortion due to charging. Imaging polymer samples with low accelerating voltages (0.1 to 2.0 keV), at or near the “crossover point”, can reduce beam damage, eliminate charging, and improve contrast of surface detail. However, at low voltage, beam brightness is reduced and image resolution is degraded due to chromatic aberration. A new generation of instruments has improved brightness at low voltages, but a typical SEM with a tungsten hairpin filament will have a resolution limit of about 100nm at 1keV. Recently, a new field emission gun (FEG) SEM, the Hitachi S900, was introduced with a reported resolution of 0.8nm at 30keV and 5nm at 1keV. In this research we are reporting the results of imaging coated and uncoated polymer samples at accelerating voltages between 1keV and 30keV in a tungsten hairpin SEM and in the Hitachi S900 FEG SEM.

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38

Bentley, J. "Interfacial Segregation Studied With Modern AEM Techniques". Microscopy and Microanalysis 3, S2 (agosto 1997): 533–34. http://dx.doi.org/10.1017/s1431927600009557.

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Abstract (sommario):

For more than 20 years interfacial segregation has been studied by analytical electron microscopy (AEM). Two recent commercial developments should allow more widespread application of 1 nm resolution AEM studies of interfacial segregation. The first is a system for integrated acquisition that in its most sophisticated form allows spectrum imaging [a full spectrum recorded at every pixel of an image (e.g. STEM)] for simultaneous multiple spectroscopies (e.g., EDS and PEELS). A field emission gun (FEG) is necessary for sufficient sensitivity at high spatial resolution. The second commercial development has been imaging energy filters that allow the production of elemental maps from a series of energy-filtered TEM (EFTEM) images at inner shell ionization edges. Resolutions of ∼1 nm can be achieved without an FEG, but analysis is limited to the electron energy-loss signal. Although complex microstructures may require full two-dimensional mapping, for many planar interfaces a one-dimensional profile of composition or chemistry normal to the interface plane is sufficient.

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39

Lanteri, S., D. Gendt, P. Barges e G. Petitgand. "Comparison of Particle Size Analyses from FEG-SEM and TEM Images". Microscopy and Microanalysis 6, S2 (agosto 2000): 380–81. http://dx.doi.org/10.1017/s1431927600034395.

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Abstract (sommario):

Much effort has recently been employed in modeling steel behavior as a function of chemical composition and thermo-mechanical processing. In order for the models to be predictive, experimental data are needed to first calibrate and then validate the calculated results. Since many steel properties are conditioned in part by the state of precipitation, this study was undertaken to provide experimental measurements of precipitates in terms of their size distributions. Due to the size range (2-100 nm) of particles which exert the greatest influence on the mechanical properties, electron microscopy is practically the only technique available for obtaining images of the precipitates.Two types of micrographs were used for image analysis in order to determine the size distribution of NbC particles present in a ternary alloy (Fe-Nb-C) heat treated at 800°C for 1000 mn. Polished surfaces lightly etched with a solution of 2% HNO3 and 98% ethanol were prepared for observations in a LEO 1550 scanning electron microscope equipped with a field emission gun.

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40

Pezzotti, Giuseppe. "Nano-Scale Stress Microscopy of Ceramic Materials Using Their Cathodoluminescence Emission". Materials Science Forum 502 (dicembre 2005): 263–68. http://dx.doi.org/10.4028/www.scientific.net/msf.502.263.

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Abstract (sommario):

An overview is given of our recent research achievements in nano-scale stress microscopy based on cathodoluminescence (CL) piezo-spectroscopy (PS) studies of ceramics. The main underlying concepts of CL nano-scale microscopy are presented, with emphasis placed on the spatial resolution of the electron probe operating at low voltages in a field-emission gun scanning electron microscope (FEG-SEM). The stress assessment technique shown here proves its general validity independent of the physical mechanisms behind the CL emission. A table, including CL spectra from impurities, defects and electron-hole recombination, is given of the stress dependence of the wavelength of selected CL bands from various ceramics of industrial use, including a reliability assessment of these dependences. Finally, some applications of nano-scale stress microscopy are shown and brief comments are offered regarding possible future evolutions and impacts on the development of new materials and devices.

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41

Navarro da Rocha, Daniel, Leila Rosa de Oliveira Cruz, Dindo Q. Mijares, Rubens Lincoln Santana Blazutti Marçal, José Brant de Campos, Paulo G. Coelho e Marcelo Henrique Prado da Silva. "Temperature Influence on the Calcium Phosphate Coatings by Chemical Method". Key Engineering Materials 720 (novembre 2016): 197–200. http://dx.doi.org/10.4028/www.scientific.net/kem.720.197.

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Abstract (sommario):

The increasing interest in the use of brushite and monetite as resorbable calcium phosphate cements or graft materials is related to the fact of these phases being metastable under physiological environment, with higher solubility than hydroxyapatite phase. In this study, X-ray diffraction (XRD) and scanning electron microscopy with field emission gun (FEG-SEM) analyses were performed in order to assess the temperature influence on the production of calcium phosphate coatings by a chemical deposition method. Titanium substrates were successfully coated with brushite and monetite by a chemical deposition method and a brushite-monetite transformation was assessed with the increasing temperature. Brushite deposition was kinetically favored at low temperatures, whereas monetite was the major phase at higher temperatures.

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42

Pezzotti, Giuseppe, Andrea Leto, Kiyotaka Yamada e Alessandro Alan Porporati. "Electro-Stimulated Piezo-Spectroscopy for Measuring Nano-Scale Residual Stress Fields in Ceramics". Advances in Science and Technology 45 (ottobre 2006): 1658–63. http://dx.doi.org/10.4028/www.scientific.net/ast.45.1658.

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Abstract (sommario):

Electro-stimulated piezo-spectroscopy (PS) can be quantitatively used for obtaining information about applied and residual stress fields piled up in ceramic materials and devices. PS experiments can be conducted in a field-emission-gun scanning electron microscope (FEG-SEM) equipped with a high spectral resolution cathodoluminescence (CL) spectrometer. Micromechanical information can be thus added to the microscopic crystallographic and chemical information already available in conventional SEM devices. Independent of the physical mechanisms behind CL emission, the spectral position of selected bands in ceramics is shown to possess high stress sensitivity. In addition, given the high scanning flexibility and spatial resolution of the electron beam, residual stress assessments can be performed on relatively large areas with significantly improved spatial resolution as compared with the more popular photo-stimulated PS approach (i.e., using a laser beam as the excitation source). In this paper, we first quantitatively characterize the stress dependence of the spectroscopic bands observed in ruby. Then, based on this knowledge, an application is shown of bi-dimensional residual stress mapping around an indentation print.

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43

Wang, Z. L., e J. Bentley. "In situ REM imaging of surface processes on ceramic bulk crystals from 300 to 1670 K in a conventional TEM". Proceedings, annual meeting, Electron Microscopy Society of America 49 (agosto 1991): 660–61. http://dx.doi.org/10.1017/s0424820100087616.

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Abstract (sommario):

Studying the behavior of surfaces at high temperatures is of great importance for understanding the properties of ceramics and associated surface-gas reactions. Atomic processes occurring on bulk crystal surfaces at high temperatures can be recorded by reflection electron microscopy (REM) in a conventional transmission electron microscope (TEM) with relatively high resolution, because REM is especially sensitive to atomic-height steps.Improved REM image resolution with a FEG: Cleaved surfaces of a-alumina (012) exhibit atomic flatness with steps of height about 5 Å, determined by reference to a screw (or near screw) dislocation with a presumed Burgers vector of b = (1/3)<012> (see Fig. 1). Steps of heights less than about 0.8 Å can be clearly resolved only with a field emission gun (FEG) (Fig. 2). The small steps are formed by the surface oscillating between the closely packed O and Al stacking layers. The bands of dark contrast (Fig. 2b) are the result of beam radiation damage to surface areas initially terminated with O ions.

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44

Cliff, G., e P. B. Kenway. "The future of AEM: Toward atom analysis". Proceedings, annual meeting, Electron Microscopy Society of America 47 (6 agosto 1989): 200–201. http://dx.doi.org/10.1017/s0424820100152975.

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Abstract (sommario):

The ultimate goal of analytical electron microscopy (AEM) is a minimum detection limit, MDL, of one atom! Utilising the small probes and the high current densities attainable using a field emission gun, FEG, in a scanning transmission electron microscope, STEM, the MDL is at present 100 atoms. This discussion will show that an MDL of 1 atom could be achieved with existing engineering technology available on the current generation of AEM instrumentation.Indeed if AEM was like hi-fi an AEM analyst could today combine features of different microscopes to build an AEM capable of atom detection!The parameters affecting the MDL include a) the electron source brightness, b) the detector solid angle, c) the operating voltage and, less frequently discussed, d) the Cs of the probe-forming lens.a) Electron source brightness. The highest brightness electron source is the FEG as used in the dedicated STEM which achieved the MDL quoted above. This is the only source capable of producing the high current density in a small probe required to reduce the MDL to atomic proportions.

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45

Czernuszka, J. T., N. J. Long e P. B. Hirsch. "Electron channelling contrast imaging of dislocations". Proceedings, annual meeting, Electron Microscopy Society of America 48, n. 4 (agosto 1990): 410–11. http://dx.doi.org/10.1017/s0424820100175181.

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In the 1970s there was considerable interest in the development of the electron channelling contrast imaging (ECCI) technique for imaging near surface defects in bulk (electron opaque) specimens. The predictions of the theories were realised experimentally by Morin et al., who used a field emission gun (FEG) operating at 40-50kV and an energy filter such that only electrons which had lost no more than a few 100V were detected. This paper presents the results of a set of preliminary experiments which show that an energy filter system is unneccessary to image and characterise the Burgers vectors of dislocations in bulk specimens. The examples in the paper indicate the general versatility of the technique.A VG HB501 STEM with a FEG was operated at l00kV. A single tilt cartridge was used in the reflection position of the microscope. A retractable back-scattered electron detector was fitted into the secondary electron port and positioned to within a few millimetres of the specimen. The image was acquired using a Synoptics Synergy framestore and digital scan generator and subsequently processed using Semper 6.

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46

Goldstein, J. I., C. E. Lyman e J. Zhang. "Spatial Resolution and Detectability Limits in Thin-Film X-ay Microanalysis". Proceedings, annual meeting, Electron Microscopy Society of America 48, n. 2 (12 agosto 1990): 450–51. http://dx.doi.org/10.1017/s042482010013585x.

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Abstract (sommario):

The major advantage of performing x-ray microanalysis in the analytical electron microscope (AEM) is the high compositional spatial resolution and the chemical analysis sensitivity. The spatial resolution (R) is dependent on the size of the focused electron probe (d) and the amount of electron beam broadening (b). The spatial resolution across a discrete interface is:The amount of beam broadening is directly proportional to the thickness (t) to the 3/2 power and inversely proportional to the beam voltage (E). Optimizing d and b involve a consideration of the minimum x-ray intensity necessary for analysis since the x-ray intensity is decreased by minimizing d and t. To obtain the optimum spatial resolution one should use the thinnest possible specimen, a high kV AEM and a high brightness field emission gun (FEG). Figure 1 shows a Ni composition profile across a planar lOnm precipitate in the plessite region of the Grant iron meteorite. A spatial resolution of 2.5nm was obtained from a 20nm thick sample analyzed in a VG Microscopes, Ltd. HB 501 FEG AEM (probe diameter 1.8nm (FWTM)).

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47

Wang, Z. L., A. Goyal e D. M. Kroeger. "Interface microstructures in melt-textured YBa2Cu3O7-δ on Ag-Pd and flux pinning centers introduced by Y2BaCuO5 particles". Proceedings, annual meeting, Electron Microscopy Society of America 50, n. 1 (agosto 1992): 72–73. http://dx.doi.org/10.1017/s042482010012076x.

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Transmission electron microscopy (TEM) and energy dispersion X-ray spectroscopy (EDS) were used to study the microstructure of the melt-textured YBa2Cu3O7-δ (123) thick films on Ag-Pd substrate. The samples used for this study were melt-textured thick films of 123 on a Ag10%Pd alloy substrate. The film was prepared using a paint-on technique and was processed according to a schedule described elsewhere, Domains of 123, as large as 5-6 mm, are formed in the film. Analytical electron microscopy (AEM) studies of this material were made using a Philips EM400 TEM/STEM (100 kV) with a field emission gun (FEG). A small electron probe of diameter approximately 2 nm was generated, and used in determining the compositional change across grain boundaries.

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48

Watanabe, M., D. W. Ackland e D. B. Williams. "Practical Estimation of Analytical Sensitivity for EDS in an Intermediate Voltage FEG-STEM". Microscopy and Microanalysis 3, S2 (agosto 1997): 965–66. http://dx.doi.org/10.1017/s1431927600011715.

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Abstract (sommario):

One of the ultimate objectives for energy-dispersive X-ray spectrometry (EDS) in the analytical electron microscope (AEM) is single-atom detection in thin specimens, as well as quantitative microanalysis with high accuracy approaching ±1% relative. In order to realize the single-atom analysis, the design of the AEM has to be optimized with respect to improvements in spatial resolution and detectability limits. The detectability limit, as defined by the minimum mass fraction (MMF), is given by:where P is the peak intensity of interest, (P/B) is the peak-to-background ratio for that peak, and r is the acquisition time. To improve the sensitivity for analysis, any or all of the variables P, (P/B), and τ should be increased. Intermediate-voltage analytical electron microscopes combined with high brightness field-emission gun (FEG) are expected to improve the MMF, while maintaining high spatial resolution. Additionally, the MMF should also be improved by maximizing the solid angle of X-ray collection.

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49

Pezzotti, Giuseppe, Atsuo Matsutani, Maria Chiara Munisso e Wen Liang Zhu. "Advanced Nano-Scale Metrology for the Characterization of Ceramic Materials in the Scanning Electron Microscope". Materials Science Forum 606 (ottobre 2008): 93–101. http://dx.doi.org/10.4028/www.scientific.net/msf.606.93.

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Abstract (sommario):

With the proliferation of several types and classes of high performance ceramic materials, the screening, evaluation and integration of new materials into structures and devices require a new and more effective approach. Evaluation on the nano-scale of the mechanical characteristics of new ceramic materials requires multiple complementary metrology tools. We report here about an advanced metrology tool, cathodoluminescence (CL) spectroscopy, which has a potential to rapidly screen and evaluate residual stress characteristics in advanced ceramic materials and structures. Nano-scale stress measurements are made in situ into an integrated metrology vacuum chamber in a field-emission gun scanning electron microscope (FEG-SEM). Complementing this tool, we also describe a new image analysis based on CL emission for fast screening and ranking of domain structures in ferroelastic ceramics. The end result of this paper is to show how crystallographic and mechanical characteristics of ceramics can be quantitatively characterized in a hybrid device combining electro-stimulated imaging and spectroscopic outputs.

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50

Yang, J. C., A. Singhal, S. Bradley e J. M. Gibson. "Nano-Sized Catalytic Materials Investigated by a STEM-Based Mass Spectroscopic Technique". Microscopy and Microanalysis 3, S2 (agosto 1997): 443–44. http://dx.doi.org/10.1017/s1431927600009107.

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Abstract (sommario):

Knowledge of catalysts' sizes and shapes on their support material is crucial in understanding catalytic properties. With increasing interest in nanosized catalytic materials, it is vital to obtain structural information at the nanometer level in order to understand their catalytic behavior. We have recently demonstrated that very high angle (˜100mrad) annular dark-field (HAADF) images in a dedicated scanning transmission electron microscope (STEM) can be used to quantitatively measure the number of atoms of individual nano-sized clusters on a support material We are presently applying this technique to a bimetallic catalyst, PtRu5, where our data suggest that the shape of the PtRu5 particle is, surprisingly, oblate on the carbon substrate.PtRu5 is of interest for methanol oxidation for applications in batteries. PtRu5 compounds were produced by a molecular precursor method. Imaging was performed on a Field Emission Gun (FEG) Vacuum Generators HB501 STEM operated at 100kV.

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