Time-Resolved Scanning Electron Microscopy and Its Application to Bulk-Effect Oscillators

The application of the scanning electron microscope to the examination of time-varying phenomena is discussed. The limitations of response time are mentioned, and methods for increasing response speed are considered. These include the use of electrostatic deflection plates to chop the primary electron beam, the use of solid-state semiconductor diodes as electron detectors, and the use of sampling and the storage and processing of data prior to display. Time-resolved techniques are then applied to a study of the motion of domains of high electric field in CdS ultrasonic oscillator diodes and in GaAs Gunn effect diodes. In both photoconducting and semiconducting CdS, the domain formation and propagation is correlated to the current waveform of the oscillator. Nonuniform domain propagation in two dimensions is examined in a GaAs oscillator.