Fast thermal-pulse measurements of space-charge distributions in electret polymers

Abstract

Space-charge depth profiles in various electret polymers have been measured in both the time and the frequency domain using thermal pulses and waves, respectively. A comparison of the two techniques on corona-charged polytetrafluoroethylene showed that the thermal-pulse method yielded similar results as the thermal-wave technique, but approximately 20–50 times faster. The article discusses sensitivity limitations as well as possible applications, including the real-time monitoring of space-charge decay under UV irradiation.

Characterisation of the polarisation state of embedded piezoelectric transducers by thermal waves and thermal pulses

“…Due to the very high gain of the current amplifier, mainly noise is present in the measured signal for measurement times of more than 0.5 ms. The signal shape is similar to the thermal pulse response of electret polymers obtained in Mellinger et al (2005), where the high-gain signal decreases to zero for times exceeding 1 ms. For further measurements, a low-pass filter and a 50 Hz notch filter will be used to reduce the noise contribution.…”

Thermal-Pulse Tomography of Space-charge and Polarization Distributions in Electret Polymers

“…For a thermal-pulse experiment, the time domain appears to be the obvious choice. However, to preserve the phase information in the signal, it is crucial to remove any phase shift introduced by the amplifier electronics [15], which is most easily done in the frequency domain. Thus, the transient thermal-pulse current I (t k ), k = 1 .…”

“…However, its relatively slow data acquisition speed often required a compromise between full depth-resolution with a limited number of in-plane data points [13], or larger, high-resolution area maps at selected modulation frequencies [12,14]. Thermal-pulse measurements, however, can be carried out up to 50 times faster than a comparable LIMM scan, as was recently demonstrated in a direct comparison [15] of LIMM and TP which showed excellent agreement between the two techniques ( Fig. 1).…”

Three-dimensional thermal-pulse probing of polarization profiles with low thermal stress

“…The transient short-circuit current carries information on the depthprofile of the polarization, while the in-plane distribution is probed by scanning the laser across the sample surface. Working in the time domain, rather than the frequency domain, has been shown to reduce data acquisition times by up to a factor of 50 [1]. The depth-resolution is typically less than 1 µm, and near-surface lateral resolutions of less than 40 µm have been reported [2].…”