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Materials characterization (SEM, TEM, XRD, XPS)

Check Bragg's law, extinction rules and lattice parameters for cubic crystals, the Scherrer equation, secondary and backscattered electrons in SEM, EDS and WDS, TEM, XPS, SIMS, and DSC and TGA with multiple-choice questions.

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XRD and Bragg's law →

Materials characterization (SEM, TEM, XRD, XPS): key points

In XRD, interplanar spacings are found from Bragg's law 2d sinθ = nλ, and for cubic crystals the extinction rules (h + k + l even for BCC; h, k and l all even or all odd for FCC) are used to index peaks and determine lattice parameters. Peak widths give an estimate of crystallite size through the Scherrer equation.

In electron microscopy, SEM secondary electron images show surface shape, backscattered electron images show compositional differences, and EDS or WDS analyzes the elements present. TEM observes the internal crystal structure and defects in thin lamellae. The chemical state of surfaces is examined by XPS, depth profiles of trace elements by SIMS, and thermal changes by DSC and TGA. Knowing how the techniques differ in information depth and sensitivity is the key to choosing among them in failure analysis.

All Materials characterization (SEM, TEM, XRD, XPS) questions (12)
  1. In XRD with Cu Kα radiation (wavelength 0.15406 nm), which value is closest to the diffraction angle 2θ of the first-order peak from the Si (111) planes, with an interplanar spacing of 0.3135 nm?
  2. In powder XRD of a metal with the FCC structure, what are the indices of the diffraction peak that appears at the lowest angle?
  3. In powder XRD of copper (FCC) with Cu Kα radiation (wavelength 0.15406 nm), the lowest-angle peak appeared at 2θ = 43.30°. Which value is closest to the lattice parameter of copper?
  4. In XRD, a peak at 2θ = 38.2° had a full width at half maximum (after removing instrumental broadening) of 0.40°. Using the Scherrer equation D = Kλ/(β cosθ) with K = 0.9 and λ = 0.15406 nm, which value is closest to the crystallite size?
  5. Which correctly describes secondary electron and backscattered electron images in SEM?
  6. Which correctly compares EDS (energy-dispersive spectroscopy) and WDS (wavelength-dispersive spectroscopy) for analyzing characteristic X-rays in SEM and EPMA?
  7. What is the main reason specimens for TEM (transmission electron microscopy) must be thinned to about 100 nm or less?
  8. Which correctly describes the information depth of XPS (X-ray photoelectron spectroscopy) and the information it provides?
  9. In XPS using Al Kα radiation (energy 1486.6 eV), the kinetic energy of Si 2p photoelectrons was measured as 1378.8 eV. If the spectrometer work function is 4.5 eV, which value is closest to the binding energy?
  10. In semiconductor failure analysis, which technique is best suited to measuring the depth profile of dopant concentration with sensitivity at the ppm to ppb level?
  11. When a polymer specimen is measured while being heated, which technique is suited to detecting the glass transition temperature Tg, and how does the transition appear?
  12. When calcium oxalate monohydrate (CaC₂O₄·H₂O, molar mass 146.1 g/mol) is heated in TGA, the water of crystallization is released first. Which value is closest to the percent mass loss in this first step? Take the molar mass of H₂O as 18.0 g/mol.

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