Surface morphology and surface chemistry of epitaxial Ir/SrTiO3/Si(001) pseudo-substrates were systematically characterized by Field Emission Scanning Electron Microscopy (FE-SEM), Atomic Force Microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS) before and after the Bias Enhanced Nucleation (BEN) of diamond. Based on these characterizations, an ellipsometric model was built taking into account both the roughening of the iridium surface and the formation of domains occurring during the BEN process. Sequential Spectroscopic Ellipsometry (SE) characterizations allowed estimating the roughening of the iridium surface, the thickness of the amorphous carbon layer and the coverage ratio of domains. By annealing the sample in air after BEN, domains were successfully removed without changing the iridium surface morphology. From these analyses, we demonstrate that SE is enough sensitive and discriminative to monitor both the formation of domains and the roughening of iridium surface, distinctly. SE can then be viewed as a powerful in situ tool of critical importance to study, monitor and finally enhance the diamond nucleation and growth on iridium for various advanced applications.