Thin Ti films were grown on silicon (100) wafers by means of a hollow cathode arc evaporation device. The layer growth was monitored in situ by monochromatic ellipsometry. Spectroscopic ellipsometry was used to characterize the as-deposited layers. The results obtained by ellipsometry were compared with those obtained using other thin film diagnostic techniques, especially X-ray photoelectron spectroscopy and Rutherford backscattering spectrometry (RBS). The integral energy influx to the substrate was monitored by measuring temperature gradients. The plasma parameters in front of the substrate were determined by means of Langmuir-probe measurements and energy resolved mass spectrometry. From the integral energy influx and the plasma parameters, the contributions of the charge carriers and heat radiation to substrate heating were calculated. Modeling of the ellipsometric measurements shows that the film density is influenced strongly by the deposition conditions. The RBS analysis supports the results of ellipsometric studies. There is a strong relation between the energy of the titanium ions striking the substrate and the layer density.