SE Signal Components

Abstract

The SE signal collection efficiency of the conventional E-T detector is limited by the asymmetry of the collection field resulting from the detector position and from the surface potential of rough specimens. Specimen biasing should be routinely applied to optimize signal collection for a given specimen and imaging situation. The voltage supply must be of extreme stability which can be provided by dry batteries such as 45-V farm batteries. Two batteries connected in series provide for an easy change of polarity. There is no rule to predict the effect of specimen biasing on signal collection. The bias modifies only the accelerating voltage of the probe and the collection field of the collector. Thus, SE components will still be collected. (Note: Only a grounded specimen grid which shields the specimen from all other biased surfaces allows establishment of a positive field between the grid and the specimen for the absorption of SE-I+II as described in experiments of Section 12.3.)