Probe sizes

Classifier structures resulting from the training were verified in a blind test. To evaluate the reliability and performance of the NSC it was subjected to a blind test using unknown data containing spectra measured for various sizes and locations of the disbonds (from 50% to over 100% of the probe size). 

Liquid or solid having optical transitions probe size 2 pm to a few cm... 

The spatial resolution of the CI SEM mode depends mainly on the electron-probe size, the size of the excitation volume, which is related to the electron-beam penetration range in the material (see the articles on SEM and EPMA), and the minority carrier diffusion. The spatial resolution also may be afiFected by the signal-to-noise ratio, mechanical vibrations, and electromagnetic interference. In practice, the spatial resolution is determined basically by the size of the excitation volume, and will be between about 0.1 and 1 pm ... 

For a fractal surface D > 2, and usually D < 3. In simple terms the larger D, the rougher the surface. The intuitive concept of surface area has no meaning when applied to a fractal surface. An area can be computed, but its value depends on both the fractal dimension and the size of the probe used to measure it. The area of such a surface tends to infinity, as the probe size tends to zero. 

The estimation of the working surface area of solid electrodes is a difficult matter owing to irregularities at a submicroscopic level.10 15 20 24 32 63 64 67 68 73 74 218-224 Depending on the irregularity-to-probe size ratio, either the entire surface or only a fraction of it is accessible to a particular measurement. Only when the size of the molecule or ion used as a probe particle is smaller than the smallest surface irregularity... 

To be more confident on alloy formation, we performed EDS compositional analysis with an electron probe size of 1 nm FWHM focused on isolated clusters as expected for bimetallic clusters, Au and Fe signals are together present in the spectrum. The measured Au/Fe atomic ratio on the largest clusters is about 1.6 0.2, indicating an Au-enriched alloy. Moreover also preliminary EXAFS spectroscopy on the sample evidenced a clear Au-Fe correlation, unambiguously confirming alloy... 

The cellular reaction product consisted of alternating plates of C03W lamellae in a solute-depleted Co matrix (eCo). Ffomogenized ingots were cut into slices 1 mm thick and then heat-treated. Spark erosion was used to trepan 3 mm diameter discs which were then jet electropolished to form thin foils for TEM examination in a Philips EM 430 STEM instrument operating at 300 kV in the nanoprobe mode with a probe size of 5 to 10 nm. 

This kind of analysis is most effectively conducted in a dedicated FEGSTEM instrument, which has an increased beam current while maintaining a small probe size. Such instruments also permit the detection of light elements such as B at boundaries. It has become possible to map the distribution of grain-boundary... 

Highest sensitivity to local concentration variations is achieved when the probe size is matched to the pixel size of the map. Figure 5.24(A) is a high magnification map of an edge-on grain boundary with 64 x 64 pixels, acquired at 2 MX with a probe size of 1 nm FWTM and a probe current of 0.5 nA. With a dwell time of 200 ms per pixel, the total frame time for this map was 0.5h. 

The mapping conditions were chosen by the authors to minimize the frame time and to maximize the counting statistics by increasing the probe size and probe current, while reducing the number of pixels in the map. These authors summarized the effect of the low-magnification mapping parameters on the measured analytical resolution for their specimen/microscope combination in Table 5.1. 

Magnification (kX) Probe size (FWTM, nm) Probe current (nA) Frame time (hr) Analytical resolution (FWTM, nm)... 

Figure 5.25. (A) Quantitative Cu map of an Al-4wt% Cu film at 230 kX, 128 x 128 pixels, probe size 2.7nm, probe current 1.9 nA, dwell time 120 msec per pixel, frame time 0.75 hr. Composition range is shown on the intensity scale (Reproduced with permission by Carpenter et al. 1999). (B) Line profile extracted from the edge-on boundary marked in Figure 5.25a, averaged over 20 pixels ( 55 nm) parallel to the boundary, showing an analytical resolution of 8nm FWTM. Error bars represent 95% confidence, and solid curve is a Gaussian distribution fitted to the data (Reproduced with permission by Carpenter...

Modern spectrometers only require electron beam currents in the range 0.1 lOnA and hence probe sizes of 20-200 nm may be readily achieved with thermionic sources and 5-15 nm with a FEG. Spatially resolved compositional information on heterogeneous samples may be obtained by means of the Scanning Auger Microprobe (SAM), which provides compositional maps of a surface by forming an image from the Auger electrons emitted by a particular element. 

These authors produced TEM samples of Bi-doped, Sb-doped and Ag-doped copper foils, thinned to electron transparency using conventional preparation procedures. In all cases the presence of impurity segregation was confirmed using conventional X-ray energy-dispersive spectrometry. The EELS measurements were carried out with a STEM operating at 100 keV, with a nominal probe size of 1 nm (full width at half maximum) with a current of about 0.5 nA. The conditions required to optimize detection sensitivity for interface analysis require the highest current density and are not consistent with achieving the smallest probes. 

Figure 1. Energy filtered experimental Si[ 110] zone axis CBED pattern. The pattern was obtained for a primary beam energy of 195.35 keV, an energy window of lOeV and an electron probe size of 1.4nm, using a Philips CM200/FEG electron microscope.

The sensitivity of Z contrast for the detection of small clusters depends not only on the signal Z dependence, but also depends on the microscope resolution, which is governed by the probe size 6. A small cluster containing N atoms of atomic number Zi, supported on a film of effective atomic number Z2 of thickness t, will have a contrast in the annular detector signal given by... 

Hummel, M.A., Tracy, T.S., Hutzler, J. M., Wahlstrom, J.L., Zhou, Y. and Rock, D.A. (2006) Influence of fluorescent probe size and cytochrome b5 on drug-drug interactions in CYP2 C9. Journal of Biomolecular Screening, 11 (3), 303-309. 

The work has shown the diversity of fluorescence-based thermometry schemes, materials, signal processing arrangements, and applications. In addition, a close agreement with theoretical predictions on material performance gives confidence to the assessment of new materials for such uses. Probe sizes are potentially smaller and more convenient due to optical source and detector developments. Thus the future for fluorescence thermometry is bright, with the expectation of a range of new ideas in the field in the future. 

The above experimental results largely relate to spectroscopic techniques, which do not give direct information about the spatial scale of the molecular motions. The size of the spatial heterogeneities is estimated by indirect methods such as sensitivity of the dynamics to the probe size or from the differences between translational and rotational diffusion coefficients (rotation-translation paradox). It might be expected that the additional spatial information provided by neutron scattering could help to discriminate between the two scenarios proposed. 

Dynamic probe methods Another indirect strategy for emalysis of gel structure is the measurement of the mobility of dynsumic probes whose sizes are well characterized. For example, dynsumic light scattering or any other method for diffusivity determination (for examples, see 37) can be used to measure the motions, through a gel matrix, of a series of spherically shaped particles with varying sizes. To oversimplify greatly, if, as probe size is raised, a dramatic decrease in diffusivity is found, then the "mesh" size of the polymer gel may be estimated. 

The absence of a plateau of constant heat in the differential heat curve can be the result of molecular interactions between molecules adsorbed at neighboring sites rather than a true indication of differences between sites [165]. This matter can be checked by varying the probe size or the site density. 

Our conclusions based on the above argument is that the appearance of new facets does not occur simultaneously with the sharp increase in surface solute concentration, but rather a few degrees below the transition. At the transition temperature, the composition of the "geometric points" which represent the orientations at which the compositional change has occurred on the rounded parts of the equilibrium form are indeed enriched in solute. However, the areas associated with the compositional change are too small to be detected by means of the 100 nm analytic probe of the SAM used in this study. The compositional changes can only be detected once the new facet has appeared, and has reached dimensions ofthe order ofthe probe size, or larger. 

Figure 10. Dependence of fractal dimension, D, on probe radii for the 12 isomers of dendrimer 6 (C = 1). The curves were obtained from the corresponding computed molecular surface areas, not depicted. The insert shows an enlargement of this dependence for a probe size range corresponding to the approximate sizes of organic molecules.

---