Analysis of the electrically stimulated acoustic-wave method for observing space charge in semi-insulating films

The electrically stimulated acoustic-wave (ESAW) method for observing resident space charge in dielectric insulators has been used to characterize the poling behavior of millimeter-thick samples of polymeric insulation. The principle involves applying a voltage pulse across a material containing space charge and recording the exiting stress-wave signal by means of a piezoelectric transducer. This is a noninvasive technique and may be performed, in situ, during any space-charge-generating experiment. This method is able to detect space charge with a figure of merit equal to the sensitivity times the resolution of 130 pC/cm2, and, to our knowledge, is the lowest reported for any nondestructive space-charge-profiling technique.