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DF: Fachverband Dielektrische Festkörper

DF 1: Dielectric and ferroelectric thin films 1

DF 1.4: Talk

Monday, March 14, 2011, 11:40–12:00, MÜL Elch

Transient surface charging of insulators — •Björn Martin, Andrey Ostroskiy, and Herbert Kliem — Saarland University, Germany

The time dependent surface potential of insulators is investigated after charging of the surface with an electrical field. The surface potential is measured contactless using a scanning Kelvin probe or the Kelvin option of an atomic force microscope (AFM).

In a first experiment, a small point on the surface of an one side metallized insulator is charged with the cantilever of the AFM. The surface potential around this point is measured afterwards. On the position of the charged point a potential difference in relation to the uncharged regions is found. A transient decay and spread of the surface potential is observed in the long time range.

In another experiment, regions around evaporated top electrodes are charged by applying linear increasing voltages. Simultaneously the charging current is measured. Peaks are found in the measured current during the charging process. After application of a short circuit the surface potential at the electrode edge is measured. A potential peak near the electrode is found. The width and the temporal decay of this potential peak depend on the electrode material. The peaks during the charging process are correlated to the appearance of the potential peak. It is remarkable and not yet understood that positive surface charges are found near the electrode edge after application of a positive voltage.