Spectroscopic Techniques for Solids

Bulk spectroscopic techniques such as x-ray fluorescence and optical and infrared spectroscopies involve minimal sample preparation beyond cutting and mounting the sample. These are discussed in Section 9.2.1. Spectroscopic techniques such as wavelength dispersive spectroscopy (WDS) and energy dispersive spectroscopy (EDS) are performed inside the SEM and TEM during microscopic analysis. Therefore, the sample preparation concerns there are identical to those for SEM and TEM sample preparation as covered in Section 9.3. Some special requirements are to be met for surface spectroscopic techniques because of the vulnerability of this region. These are outlined in Section 9.5. 

In recent decades we have seen an explosion of various spectroscopic techniques for analyzing the elemental composition and chemical states of solid surfaces and films. This explosion has stemmed in part from the large number of surface- or interface-related problems seen in integrated-circuit performance, composite reliability, corrosion, nanostructured components, and so on. Instruments themselves can range from stand-alone units to attachments in national synchrotron facilities or multitechnique systems built around special fabrication sites. However, the basic principle of the technique, and therefore the basic concerns with sample preparation, stay the same. 

The most obvious requirement, of course, is that the specimen be cut to size. The size depends on the microscope and could range from a few centimeters in a normal SEM to a few inches in a specially designed SEM. In TEM, of course, since the thickness is extremely low and the sample needs to be on a grid or support, the specimen is normally a few millimeters in size. Ductile metals are sometimes rolled into sheets before cutting into the desired size. It needs to be kept in mind that this process itself will lead to defect creation and microstructural changes that need to be annealed out [11], Some polymers and composites are easily available as sheets anyway, so this step is not of any concern. In the large variety of bulk materials that it is not possible to form into sheets, sectioning the sample to a thin slice is the only way to start. 

Technique Information Obtained Detected Depth Width 

Cutting wheels or wires with abrasives Aluminum oxide abrasives Silicon carbide abrasives i r Diamond abrasives 

---