Back-scattered electron microscopy

Primmer T. J. and Shaw H. F. (1987) Diagenesis in shales evidence from back-scattered electron microscopy and electron microprobe analyses. Proc. Int. Clay Conf, Denver, CO, vol. 8, pp. 135-143. 

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. 

Figure 8.5 Varnish micromorphology form ranges from botryoidal to lamellate (A and C). Two types of imagery show botryoidal varnishes from Kitt Peak, Arizona (A) the topography by secondary electrons (B) the same structures from the bottom upwards with back-scattered electrons - showing the layering structures inside each nudeation centre. (C and D) Scanning electron microscopy images of lamellate clay minerals accreting on rock varnish in Death Valley, California. (C) Individual clay platelets overlap as they cement onto the surface. (D) The clays impose a lamellate structure in cross-section, as first noticed by Potter and Rossman (1977).

Microscopy, Atomic force (AFM) 191, 193, 316, 429, 572, 1192, 1194, 1373 Microscopy, back-scattered electron image 547, 556 Microscopy, confocal 548... 

After curing, the casting is relatively inert and should be very hard. This can be mounted, cut, ground and polished to give a polished thin section for optical microscopy or SEM work. This polished thin section should be carbon-coated before examination in the SEM using a back-scattered electron detector. 

Use of the microanalysis attachment in conjimc-tion with electron microscopy can provide a visual representation of concentrations. When finked to nondestructive preparation techniques, such as critical point drying, this offers the potential of assessing specific soil processes. Adamo et al. used scanning electron microscopy in back-scattered electron mode to examine the soil-root interface of plants grown at a range of soil pH and soil phosphorus concentrations. Excellent spatial resolution is, however, covm-terbalanced by relatively poor detection limits due to poor spectral resolution resulting in severe peak overlap. 

In scanning electron microscopy, electrons emitted by an electron gun (primary electrons) are focused by means of Wehnelt cylinders and electromagnetic lenses onto the sample surface, which they scan line by line (Fig. 2). The secondary and back-scattered electrons emitted by the sample are captured by detectors and presented in the form of brightness modulation on, eg, a monitor. The secondary electrons come from a surface layer up to 10 nm thick, while the back-scattered electrons usually originate from deeper layers. 

Figure 13. Scanning Electron Microscopy image (Back scattered electrons mode) of a zirconia toughened alumina nano composite, showing the narrow distribution of well dispersed zirconia particles in an alumina matrix [39],...

---