In situ spectroscopic ellipsometry studies of trivalent chromium coating on aluminum

In situ spectroscopic ellipsometry in the spectral region of 1.3-4.3 eV has been employed to monitor, in real-time, the formation of trivalent Cr process (TCP) conversion coatings on polished Al substrates. The measured ellipsometry parameters (Psi and Delta), as a function of immersion time, reveal that the initial stages of film formation include the chemical thinning of the native oxide layer, formation of a very thin initiation layer and the subsequent rapid formation of the TCP film. The film optical constant is modeled using Cauchy dispersion relation and its thickness was determined as a function of immersion time during growth. (C) 2010 American Institute of Physics. [doi:10.1063/1.3511472]