Scanning electron microscop sample preparation

Electron Beam Techniques. One of the most powerful tools in VLSI technology is the scanning electron microscope (sem) (see Microscopy). A sem is typically used in three modes secondary electron detection, back-scattered electron detection, and x-ray fluorescence (xrf). AH three techniques can be used for nondestmctive analysis of a VLSI wafer, where the sample does not have to be destroyed for sample preparation or by analysis, if the sem is equipped to accept large wafer-sized samples and the electron beam is used at low (ca 1 keV) energy to preserve the functional integrity of the circuitry. Samples that do not diffuse the charge produced by the electron beam, such as insulators, require special sample preparation. 

Replication avoids the problem of sample deterioration in the instrument, but it is destructive in that reaction of the material cannot be continued after the replica has been prepared. Transitory features cannot be detected unless a series of preparations are examined corresponding to increasing progress of the reaction considered. The textures of replicas have been shown [220] to be in satisfactory agreement with those of the original surface as viewed in the scanning electron microscope. The uses and interpretations of observations made through sample replication procedures are illustrated in the studies of decomposition of metal carboxyl-ates by Brown and co-workers [97,221—223]. 

FIGURE 3.14 Transmission electron microscopic (TEM) pictures of (a) acrylic rubber (ACM)-silica hybrid prepared from 1 1 tetraethoxysilane (TEOS)/water (H2O) and (b) 1 2 TEOS/H2O mole ratios and (c) scanning electron microscopic (SEM) picture of ACM-silica hybrid composite synthesized from 1 6 TEOS/H2O mole ratio. The concentration of TEOS has been kept constant at 45 wt% and the samples have been gelled at room temperature. (From Bandyopadhyay, A., De Sarkar, M., and Bhowmick, A.K., J. Appl. Polym. Sci., 95, 1418, 2005. Courtesy of Wiley InterScience.)... 

First of all, only the samples, prepared according to the procedure (a) were suitable for scanning electron microscope (SEM) measurements. All other samples were very un-... 

Sample Preparation. The basalt was crushed and sieved, and the -120 + 230 mesh fraction was used. The grains were ultrasoni-cally washed in deionized water to remove very fine adhering particles. If these particles are not removed, they will preferentially dissolve under hydrothermal conditions, resulting in abnormally high rates of mineral-fluid reactions (10). Examination of samples of the basalt on a scanning electron microscope assured that all fines had been removed. Nitrogen B.E.T. specific surface area of the washed basalt was 2.7 m2/g. 

The polished samples are sputtered with a thin layer of gold for analysis in a scanning electron microscope (SEM), a Jeol JSM 35c fitted with a link AN 10000 energy-dispersive X-ray spectrometer (EDS). The fractured surfaces and polished sections through fractured specimens can also be prepared and analysed in this manner. SEM analysis may reveal a non-uniform fibre distribution in the composite. In composites sintered at different temperatures, cracking in the matrix phase and residual porosity can be identified and the filler particles are discernible. The EDS indicates the higher particles and the matrix constituents. 

It can be seen that most of the electrons are localized in the 3.5 pm thick layer and only a few of them penetrate to a depth of 3.8 pm. In our experiments a 0.5 mm thick LiNbC>3 crystal was spin-coated with 3.5 pm thick photoresist layer (Shipley 1818). The prepared sandwiched structure was exposed using a commercial eb lithography system (elphy Plus) adapted to a jeol jsm 6400 scanning electron microscope on the C -face of the LiNb03 sample under various accelerating voltages and surface charge densities, as shown in Table 10.1. 

There are also catalyst formulations which have highly dispersed metals which are deliberately heterogeneously distributed on a support. If the microscopist is aware of the situation, he can take precautions in the sample preparation. This type of sample is the worst possible case to analyze because not only does the analyst have a complex mixture of components to sort out, but the analysis statistics are very poor. Consequently, additional time is usually required to survey the catalyst particles in order to establish a consensus of how it was constructed. Specialized specimen preparation such as ultramicrotoming and scraping the exterior of a sphere or extrudate may alleviate some of the interpretation problems. Additional aid may be solicited from a scanning electron microscope wherein an elemental distribution of a polished cross section of the catalyst sphere or extrudate can be made. 

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