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CPP: Chemische Physik und Polymerphysik
CPP 13: Dünne Polymerfilme
CPP 13.6: Vortrag
Donnerstag, 27. März 2003, 11:30–11:45, ZEU/118
UV Photo-Stimulated Discharge and its Influence on the Piezoelectric Coefficient of Cellular Polypropylene Films — •Francisco Camacho González, Axel Mellinger, and Reimund Gerhard-Multhaupt — Institut für Physik, Universität Potsdam, Am Neuen Palais 10, 14469 Potsdam
In recent years, corona-charged cellular polymer electrets [1] have received considerable attention because of their large piezoelectric coefficients. Moreover, the charges stored on the inside of the oblate voids provide a suitable system to study the mechanisms of charge trapping and detrapping. With photo-stimulated discharge (PSD) spectroscopy, three distinct trap levels could be identified in polypropylene (PP) foams at wavelengths of 198, 223 and 290 nm. Changes in the space-charge distribution were measured using the laser-intensity modulation method (LIMM). In addition, the thickness-extension resonance in the dielectric spectrum provides a precision technique for in-situ measurements of the piezoelectric d33 coefficient under UV exposure. Prolonged irradiation at 198 nm resulted in a decreased d33, whereas no changes where observed during irradiation at the other two peak wavelengths in the PSD spectrum [2]. This suggests that the charges stored in the voids are located in very deep traps at 6.3 eV.
[1] M. Paajanen, J. Lekkala and K. Kirjavainen, Sensors and Actuators 84, 95-102 (2000)
[2] A. Mellinger, F. Camacho González and R. Gerhard-Multhaupt, Appl. Phys. Lett., in press