[en] The nucleation of copper on TiN and SiO₂ surfaces has been investigated using a collimated molecular beam of hexafluroacetylacetonate copper(I) trimethylvinylsilane in ultrahigh vacuum. The Cu thin film precursor was delivered using a bubbler with H₂ as the carrier gas and the substrate temperature was varied from 150 to 260 deg. C. Ex situ analysis of thin film morphology and microstructure has been conducted using scanning electron microscopy. On SiO₂ surfaces the Cu nuclei density reaches a maximum near 5x10¹⁰ cm^-2, nearly independent of substrate temperature. In contrast, on TiN surfaces the maximum nuclei density is strongly dependent on temperature, varying nearly two orders of magnitude from 150 to 260 deg. C. On TiN the nucleation process is described well by established kinetic models where a maximum in nuclei density (N_max) is predicted with respect to the time, and where this quantity exhibits an Arrhenius dependence on substrate temperature