Polyaniline (PAni) thin films were deposited onto BK7 glass substrates using the in situ deposition technique. The control of the time and the aniline concentration in the PAni polymerization reaction on the film deposition allowed us to prepare films with different thickness, down to similar to 25 nm. The film growth process was monitored by measuring the UV-vis spectra and the AFM height profiles of the film surface. The curves of adsorption kinetics were analyzed with the Avrami's model, yielding an exponent it n = 3, thus indicating nucleation of spheroids at the initial stages of polymerization that grow through a diffusion process. AFM images of the surface height profiles corroborate this hypothesis, with spheroids growing with no preferred orientation during the in situ deposition. (C) 2007 Elsevier Inc. All rights reserved.