The GATE Grind

GATE 2019 MT – Question 40

Physical Metallurgy · Materials characterization · 2 marks · Multiple choice

In an SEM image, topographic information and atomic-number contrast are primarily obtained from which signals, respectively?

  1. Secondary and Auger electrons
  2. Primary and secondary electrons
  3. Secondary and backscattered electrons
  4. Backscattered and Auger electrons

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Correct answer: (C) Secondary and backscattered electrons

Explanation

Low-energy secondary electrons escape from a shallow region and strongly reveal surface topography. Backscattered-electron yield depends on atomic number, producing compositional contrast. Thus C. Auger electrons are chiefly useful for surface elemental spectroscopy in this comparison.

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