Design and construction of an atmospheric or environmental SEM (part 3)

The continuation of the advances in designing and constructing an atmospheric or environmental SEM (ASEM and ESEM, respectively) is reported. A pair of scintillator backscattered electron detectors have been designed and made so that signal processing to enhance topography and Z‐contrast can be performed. Optimum shapes and positioning of the detectors have been determined. The light transmittance in the light pipe has been mapped and measured to be 51%. Satisfactory signal‐to‐noise ratio images of a carbon specimen have been obtained with 5 kV, 2 pA and 50s scan time at 0.1 mbar. With a higher intensity beam, clear images of wool fibres have been achieved at 1 bar pressure. The ASEM and ESEM have been shown to operate both under conditions of a gaseous environment and with detection modes used in other microscopes. Changes and phenomena occurring as the relative humidity varies between 0 and 100% have been recorded.