Weak Localization in Semiconducting Polymer Thin Film Devices
Abstract
We have performed magnetoresistance measurements on a set of polyfluorene sandwich devices as a function temperature, applied voltage and magnetic field, B<100mT. These devices were prepared with varying polymer film thickness and using different electrodes. We observed both positive and negative magnetoresistance with magnitude of several per cent under different operation conditions. The magnetoresistance curves obey the functional dependence characteristic of weak localization and antilocalization which is well known to occur in the diffusive transport in metallic and semiconducting samples. Particular attention is paid how to experimentally extract the phase breaking and spin orbit coupling lengths. Fits to the data confirmed that the width of the magnetoresistance in weak magnetic field, whether a weak localization or weak antilocalization peak, was determined by phase breaking length. We find that phase breaking lengths exceed 100nm at room temperature. The magnitude of the magnetoresistance depends on the device resistance in agreement with the prediction from theory. However, upon reducing the device resistance the magnitoresistance effect does not tend to zero, as predicted by weak localization theory, but changes sign indicative of the presence of spin-orbit coupling.
- Publication:
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APS March Meeting Abstracts
- Pub Date:
- March 2004
- Bibcode:
- 2004APS..MARH30007M