Conducting polymers as electron glasses: Surface charge domains and slow relaxation

The surface potential of conducting polymers has been studied with scanning Kelvin probe microscopy. The results show that this technique can become an excellent tool to really 'see' interesting surface charge interaction effects at the nanoscale. The electron glass model, which assumes that charges are localized by the disorder and that interactions between them are relevant, is employed to understand the complex behavior of conducting polymers. At equilibrium, we find surface potential domains with a typical lateral size of 50 nm, basically uncorrelated with the topography and strongly fluctuating in time. These fluctuations are about three times larger than thermal energy. The charge dynamics is characterized by an exponentially broad time distribution. When the conducting polymers are excited with light the surface potential relaxes logarithmically with time, as usually observed in electron glasses. In addition, the relaxation for different illumination times can be scaled within the full aging model.This work has been funded by the Ministerio de Economia y Competitividad and (MINECO, Spain) FEDER (EU)through the projects FIS2012-38206, CSD2010-00024 and ENE2013-48816-C5-1-R -C02-01 and by the Fundacion Seneca 15324/PI/10 and 19907/GERM/15. EE and ELE thanks the MINECO programs MAT 2006-12970-C02-01, CSD2010-00024 for the financial support. EPL thanks the Ramon y Cajal program RyC2010.Peer reviewe