Electron-beam techniques

Modem instmments use all of these signals to extract information about a sample. These include the scanning electron microscope, the transmission electron microscope, the electron microprobe, and the auger nanoprobe. For many of these techniques, a conductive 

Scanning electron microscopes can be equipped with a CL detector. Cathodolumines-cence provides information on the mineralogy of a sample. An electron backscatter 

The has found wide use in studying presolar grains, IDPs, and Stardust samples, and in analyzing the fine-grained alteration minerals in carbonaceous chondrites. 

Electron microprobes can be used in spot mode to measure the chemical compositions of individual minerals. Mineral grains with diameters down to a few microns are routinely measured. The chemical composition of the sample is determined by comparing the measured X-ray intensities with those from standards of known composition. Sample counts must be corrected for matrix effects (absorption and fluorescence). The spatial resolution of the electron microprobe is governed by the interaction volume between the electron beam and the sample (Fig. A.l). An electron probe can also be operated in scanning mode to make X-ray maps of a sample. You will often see false-color images of a sample where three elements are plotted in different colors. Such maps allow rapid identification of specific minerals. EMP analysis has become the standard tool for characterizing the minerals in meteorites and lunar samples. 

As with the electron microprobe, the chemical composition is determined through comparison with standards. Corrections for interactions with different elements are also necessary. However, the standardization and correction procedures for the AES are much less mature than those for the electron probe. In cosmochemistry, the auger nanoprobe is used primarily to determine the chemical compositions of presolar grains. It is ideal for this application because it is a surface technique and has the same spatial resolution as the NanoSIMS (see below), which is used to identify presolar grains in situ in meteorite samples and IDPs. 

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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. 

Overall a customer needs to know under what circumstances it is best to use either the electron-beam techniques of EDS and WDS or the X-ray technique of XRF for an analysis problem. If both are equally available, the choice usually resides in whether high spatial resolution is needed, as would be obtained only with electron-beam techniques. If liquids are to be analyzed, the only viable choice is XRF. If one s choice is to use electron-beam methods, the further decision between EDS and WDS is usually one of operator preference. That is, to commence study on a totally new sample most electron-beam operators will run an EDS spectrum first. If there are no serious peak overlap problems, then EDS may be sufficient. If there is peak overlap or if maximum sensitivity is desired, then WDS is usually preferred. Factored into all of this must be the beam sensitivity of the sample, since for WDS analysis the beam current required is lO-lOOx greater than for EDS. This is of special concern in the analysis of polymer materials. 

The classical approach for determining the structures of crystalline materials is through diflfiaction methods, i.e.. X-ray, neutron-beam, and electron-beam techniques. Difiiaction data can be analyzed to yield the spatial arrangement of all the atoms in the crystal lattice. EXAFS provides a different approach to the analysis of atomic structure, based not on the diffraction of X rays by an array of atoms but rather upon the absorption of X rays by individual atoms in such an array. Herein lie the capabilities and limitations of EXAFS. 

It can be welded by resistance, tungsten-inert gas (TIG), plasma arc and electron beam techniques. To protect the metal from attack by air, resistance welding is carried out under water and the TIG method is best performed in a chamber of argon. The latter three methods produce ductile welds that equal the base metal in most of its characteristics. 

Micro- (and even nano-) electrode arrays are commonly produced with photolithography and electronic beam techniques by insulating of macro-electrode surface with subsequent drilling micro-holes in an insulating layer [136, 137], Physical methods are, however, expensive and, besides that, unsuitable for sensor development in certain cases (for instance, for modification of the lateral surface of needle electrodes). That s why an increasing interest is being applied to chemical approaches of material nanostructuring on solid supports [140, 141],... 

In a study of long range ET between aromatic donor (biphenyl) and acceptor molecules separated by steroid spacers [39], pulse radiolysis and electron beam techniques have been used for the injection of electrons (Closs and Miller, 1988 Closs et al., 1989 Liang et al, 1990). Here, the reaction rates (observed by changes in the absorption spectra) pass through a... 

Equations (8.27) and (8.28) indicate that d>(0) will tend to be more positive for a crystal containing heavier atoms. This is confirmed by experimental measurements of (0) using electron-beam techniques. Measurements by electron holography, for example, give the following values for a number of crystals Si,... 

PIXE is a technique that uses a MeV proton beam to induce inner-shell electrons to be ejected from atoms in the sample. As outer-shell electrons fill the vacancies, characteristic X-rays are emitted and can be used to determine the elemental composition of a sample. Only elements heavier than fluorine can be detected due to absorption of lower-energy X-rays in the window between the sample chamber and the X-ray detector. An advantage of PIXE over electron beam techniques is that there is less charging of the sample from the incoming beam and less emission of secondary and auger electrons from the sample. Another is the speed of analysis and the fact that samples can be analyzed without special preparation. A disadvantage for cosmochemistry is that the technique is not as well quantified as electron beam techniques. PIXE has not been widely used in cosmochemistry. 

Sonic of the supcralloys can lie welded hy arc melting processes, as well as hy resistance and electron-beam techniques. Alloys having low contents are reudily weldable. 

Electron beam techniques have aided electrical measurements greatly, but these methods often lack sensitivity (X-ray and Auger spectroscopy and ESCA [electron spectroscopy for chemical analysis]) and accuracy (SIMS [secondary-ion mass spectrometry], etc.), two attributes that are of prime importance in IC process technology. Fortunately, materials can be analyzed with both accuracy and sensitivity by wet chemical analysis. 

Only by application of the electron beam technique in connection with cationic catalysts like triarylsulfonium or diaryliodonium hexafluoroantimonates, hexa-... 

In the face of this complexity there are few analytical techniques which do not apply1 An advanced iC process will utilize traditional bulk chemical analysis, i.e. chromatography, spectroscopy, titrimetry, etc., as well as the array of ion and electron beam techniques for thin film and small spot analysis. 

We need also to take into account that some materials are incompatible with technological methods used for microelectronic designs (Blinker and Scherer 1989 Randhaw 1991 Hitchman and Jensen 1993 Bunshah 1994 Hecht et al. 1994 Glocker and Shah 1995 Arthur 2002 Choy 2003 Christen and Eres 2008 Jaworek and Sobczyk 2008). For example, during polymer sputtering using electron-beam techniques, chemical decomposition of polymers is possible, which naturally limits the application of such materials. 

Subjecting a metal surface to an intense beam of light, such as that from a laser, can cause electrons to be ejected from the metal. As in the case of the electron beam, a very small current flow can be induced. Again a vacuum is required (so that the ejected electrons can be measured before they collide with air molecules), though the vacuum requirement is less stringent than that for the electron beam technique. The resistance at which continuity measurements can be made is quite limited, as in the case of the electron beam. (See discussion of electron beam method in Sec. 39.9.1.) Again, test speed suffers due to product capacitance. No practical system has resulted from investigative work. 

The electron beam technique has often been utilized for surface modification and properly improvement of polymer materials like fibers, films, plastics, and composites in recent decades [104-107]. It may remove surface impurities and alter surface chemical characteristics at an appropriate irradiation condition. Electron beam processing is a dry, dean, and cold method with advantages such as energysaving, high throughput rate, uniform treatment, and envirorunental safety. 

The thermodynamic properties of UC2 have been studied by several scientists. Coninck et al. (1976) conducted experiments on UC2 and provided correlations for the calculation of the thermal diffusivity, thermal conductivity, and emissivity of UC2 as functions of temperature. Coninck et al. (1976) used the modulated electron beam technique in order to determine the thermal diffusivity of UC2 samples. In this technique, an electron gun is used to bombard a material in the form of a thin solid plate from one face. The electron gun is modulated to vary sinusoidally as a function of time. The phase difference between the temperature fluctuations of the two faces of the plate is measured, which is used to determine the thermal diffusivity of the material (Wheeler, 1965). Then, thermal conductivity is calculated as the multiplication of thermal diffusivity, density, and speciflc heat as shown in Eq. [18.3]. 

Wheeler, M.J., 1965. Thermal diffusivity at incandescent temperatures by a modulated electron beam technique. British Journal of Applied Physics 16, 365—376. 

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