The electrochemical growth of conducting polymer “nanowires”

We report on the electrochemical growth of a PEDOT wire across the gap between two gold electrodes patterned on a glass substrate. We delineate areas of the parameter space (alternating field frequency and amplitude, monomer concentration, solvent, electrolyte conductivity) where single wires, multiple wires and nodular deposits may form and discuss the mechanisms for morphology control. Faradaic rectification drives the electrochemical growth, whilst the AC field determines the electrode boundary conditions and hence the current distribution. Another critical determinant of the deposit morphology is directed convection, also stimulated by the alternating field. Raman microscopy revealed a variation in doping level of the polymer wire along its length, which we attribute to solution transport-limitation of the dopant anion to the growing wire tip.