DIFFERENTIAL CONTRAST IMAGING OF SECONDARY-ELECTRON SIGNALS IN CRYO-FIELD-EMISSION SCANNING ELECTRON-MICROSCOPY

Low-temperature scanning electron microscopy (LTSEM) is limited in res olution and image duality by char,qing of frozen hydrated samples and collection deficiencies of secondary electron signal contrasts, We mea sured and corrected both effects using differential hysteresis process ing (DHP) of LTSEM images, scanned at 15-bit from 5 x 4 inch Polaroid negatives. Bulk charging produced a major contrast component equal to 44-87% of the intensity range of the image. The strong charging contra st reduced the local high-resolution signal contrasts to an unrecogniz able level. Segmentation and imaging of the unaffected surface contras ts produced high-quality images of high contrast from metal-coated sam ples as well as from uncoated samples. The differential contrast imagi ng can be used for control of the sequential etching of ice from the n on metal-coated sample as well as improved LTSEM imaging of the finall y coated sample.