We report on a study of the electrical-transport properties of monolayers of phthalocyaninepolysiloxane (PcPS) polymers, and evaluate their potential for use as molecular wires. Monolayers have been deposited with the Langmuir-Blodgett technique on top of Si/SiO2 substrates with interdigitated electrodes. Current-voltage curves have been measured as a function of temperature for samples with varying electrode distance and number of monolayers. In the undoped state, the conduction is well described by the space-charge-limited-current model. From the data we obtain material characteristics such as the density of trap states within the gap and an estimate of the charge-carrier mobility. It appears that the conductivity is too low to yield a measurable current through a single PcPS polymer. Chemical doping and a field effect have been investigated. Oxygen is effective in doping the PcPS layers, resulting in a two orders of magnitude increase of the conductivity. Iodine is not effective as a dopant. By application of a voltage on a back-gate, we observe a field-effect-induced increase of the conductivity by three orders of magnitude. The effect however decays rapidly in time.


Tans, S., Miedema, R. G., Geerligs, L. J., Dekker, C., Wu, J., Neher, D., & Wegner, G. (2003). Electronic transport in monolayers of phthalocyanine polymers. Nanotechnology, 14, 1043–1050.