Atomic force microscopy surface morphology studies of ‘in situ’ deposited polyaniline thin films

An ‘in situ’ deposition method is presented where combination of solutions of aniline monomer and an oxidizing agent leads to the growth of uniform polyaniline (PAn) conducting thin films on submerged substrates. The PAn films can be deposited on a variety of substrates including glass and organic materials. Film thickness can be controlled by varying the duration of the substrate dipping time; about 300 Å was produced during a dipping time of 5 min. Atomic force microscopy (AFM) was used to analyze the PAn film surface morphology and roughness. AFM images of the PAn surfaces revealed very smooth surfaces having a surface roughness (mean and root mean square) of about 30 Å. Measurements on the PAn films using UV, visible and near IR were consistent with the thickness measurements obtained with AFM. The PAn film surface morphology, as determined from AFM images, was found to be characterized by particle-like features of about 50 to 100 nm in size which were packed tightly to produce a high density structure. Using a four-probe measurement approach, the conductivity of the doped PAn films was determined to be 2–6 S/cm.