Scanning Electron Microscopy is a non-destructive technique. It uses a beam of high energy electrons generated by an electron gun which inturn is focussed and systematically scanned (raster) across the surface of a specimen via a set of magnetic lenses. The accelerated electrons from the source carry a known amount of kinetic energy and this dissipates into many signals via electron-scattering interactions within the sample and produces different phenomena as follows.

Secondary electrons thus produced gives rise to surface morphological images and tracked using Everhart Thornley detector.

High energy Back Scattered Electrons thus produced and detected using BSED shows the spatial distribution of the elements and also distinguish them based on the lighter and heavier atoms by varying the contrast.

Characteristic X-rays generated from the specimen and detected using Si(Li) detector gives rise to information pertaining to the elemental composition of the sample. The specimen also produces continuum x-rays, auger electrons, visible light (Cathodoluminescence) and heat.

Besides this, the characteristic x-ray photons excited by the electron beam can also be sorted using a diffracting crystal, whose angular placement relative to the sample and photo detector is a unique measure of their wavelengths. This is termed as PBS (WDS) and by comparison with standards the material formulation can be found out. Using this technique the elemental composition in the range ppm-0.1% can be detected.

INSTRUCTIONS:

• Samples should be completely dried.
• Oil/Wax/Resins/Liquid crystals/Degassing/Emulsion/Moisture absorbing samples cannot be analysed.
• Magnetic samples should be pelletized.
• All liquid samples should be dried over a glass slide/cover slip.
• Gold sputter Coating will be done only for non-conducting samples.