Field emission gun scanning transmission

Results are often converted to an equivalent monolayer coverage for direct comparison with field emission gun scanning transmission electron microscopy (FEGSTEM) EDX measurements of grain boundary segregation. The calculation is straightforward for binary systems, but the complexity rapidly increases as the number of elements increases. The equivalent monolayer coverages (O) for P and C in Fe are summarised in Table 92 ... 

FEG-STEM ( field emission gun - scanning transmission electron microscopy ) 147... 

Transmission electron microscopy (TEM) has traditionally been the mainstay of morphological investigations of polyolefins [8], but recent developments in low voltage high-resolution field emission gun scanning electron microscopy (FEG-SEM) [9] and the advent of atomic force microscopy (AFM) and related near-field techniques [10] have challenged its dominance at the length scales of the order of 10 nm, characteristic of both microdeformation (cavitation, fibrils) and structural components of semicrystalline... 

The degree of clay dispersion in a PS matrix was characterized by x-ray diffraction analysis (XRD), and electron microscopy that is, scanning [with field emission gun scanning electron microscopy (FEGSEM)] and transmission (TEM) the results are listed in Table 14.1. The XRD scans were obtained at a scan rate 0.3°/min. The specimens were prepared by compression molding at T= 200°C and a compressive... 

Besides the conditions of acid hydrolysis, the morphology and dimensions of the NCC also depend on the source from which they were extracted. Some of the main techniques used in the investigation of size and/or morphology of these nanofibers are dynamic light scattering (DLS), scanning electron microscopy with a field emission gun (FESEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM) [22,25,67,68,69]. 

Resolution in the STEM is limited by the probe diameter, which is about 1 nm in equipment dedicated to this operating mode, at the cost of using a cold field emission gun requiring an ultravacuum. Because of the high-precision optics and the point-by-point image formation principle, the STEM combines the advantages of scanning electron microscope analysis with resolution performance levels similar to the transmission electron microscope. 

With modern scanning electron microscopes many of the restrictions of the transmission electron microscope have been alleviated. Firstly, thin samples are no longer required. With instruments equipped with a field-emission gun, magnifications as low as 50X and as high as lOOOOOX can be achieved routinely. Imaging the back-scattered electrons gives the distribution of the heavy elements at a high resolution, whereas the secondary electrons are indicative of the shape and the size of the solid particles present in the specimen. Analysis of the emitted X-rays can indicate the elemental composition. 

The electron microscopes can be divided into two types (166) scanning electron microscopes (SEM), which use a 10-nm electron beam at the specimen surface, and transmission electron microscopes (TEM). With current TEMs, resolution of about 0.2 nm can be achieved, provided very thin (<20 nm) samples are available. With conventional inorganic oxide-supported metal catalysts, particles of approximately 1 nm can be detected. Scanning transmission electron microscopes (STEM) use a high brightness dark-field emission gun to produce a probe about 0.3 nm in diameter and combine the techniques of SEM and TEM. Further experimental and theoretical aspects of electron microscopy applied to catalysis have been reviewed recently (113, 167-169). 

The technique involves a scanning transmission electron microscope (STEM) and a high brightness electron source, a field emission gun (FEG to ensure sufficient current in a l-2nm diameter probe to excite a useful X-ray intensity. 

If the TEM is being used in scanning transmission electron microscopy (STEM) mode or for analysis using a small probe (and the souree is not a field emission gun [FEG]), then the first part of the objective lens is used as a strong condenser lens to demagnify the source a lot and focus the illumination onto the specimen. The second condenser is turned off in this mode. Parallel illumination in this type of instrument is obtained by using C2 to focus the source on... 

The cross-section and surface morphology of the prepared films were examined using scanning electron microscopy (SEM) (Hitachi S-3000N) and transmission electron microscope (TEM) (FEI E.O Tecnai F20 G2 MAT S-TWIN Field Emission Gun) The phase identification of the prepared films was characterized by X-ray diffracotnneter (XRD). The patterns were recorded on a Rigaku MultiHex diffractometer with Cu Ko radiation. 

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