Strategies for optimum use of superposition diffractogram in scanning electron microscopy

Characteristics of the superposition diffractogram used for precisely estimating scanning electron microscopy (SEM) resolution are investigated. It is shown that the choice of pixel density to satisfy the sampling theorem, the direction of scanning, the choice of image shift direction, the properties of the specimen, the effect of external disturbances such as vibration and stray magnetic fields, and the effect of the window function required in the Fourier transform, are all factors which must be considered in order to make the superposition diffractogram a practical technique. An additional important improvement required to exploit fully the ability of the superposition diffractogram, which potentially is very high, is a special scanning mode which employs a digital scan generator, and digital image processing technology with autocorrelation functions.