Heteroepitaxial diamond grown on iridium buffer layer has been proven to have a promising potential for diamond based electronic devices [1,2] and sensors. Heteroepitaxy has the potential to unlock the path towards large-area single-crystal diamond substrates. The use of thin SrTiO3 films epitaxially grown on silicon is a great alternative for up-scaling [3]. The understanding of the effect of different parameters of the BEN (Bias Enhanced Nucleation) process is crucial for future single-crystal diamond up-scaling. Several nanometers thick (30-40nm) SrTiO3 films deposited by MBE on silicon (001) has been used as substrates. High quality iridium layers with a thickness of 100-200nm were grown on these 5x5mm2SrTiO3/Si multi-layer substrates by e-beam evaporation (M-EV) at 700°C [4]. The FWHM of the rocking curve (ω) and the azimuthal curve (ϕ) of the iridium film measured by XRD were 0.33° and 0.09° respectively. Effects of different BEN parameters, such as the bias voltage (-270V to -307V), the mole fraction of methane (2% to 6%), the microwave power (400W to 550W) and the pressure (15mbar to 25mbar) were studied while other parameters are kept identical. On iridium, diamond nuclei are formed during BEN in localized areas called domains [5]. The variation of BEN parameters led to the formation of domains with different homogeneity, surface coverage and shape, The surface coverage of the domains on iridium has been calculated by image analysis considering several hundreds of HRSEM (Scanning Electronic Microscope) images. The highest coverage of the domains obtained during this study was 98% and it was obtained with 4% of CH4 at 20mbar and a microwave power of 500W by applying a bias voltage of -290V. A 260nm thick, homogeneous and covering diamond film template was grown on this sample for XRD and Raman analysis. [1] D. Takeuchi, et al., Free exciton luminescence from a diamond p–i–n diode grown on a substrate produced by heteroepitaxy, Phys. Status Solidi A, 211, No. 10, 2251-2256, 2014 [2] H. Kawashima, et al., Electronic properties of diamond Schottky barrier diodes fabricated on silicon-based heteroepitaxially grown diamond substrates, Applied Physics Express, 8, 104103, 2015 [3] T. Bauer, et al., Growth of epitaxial diamond on silicon via iridium/SrTiO3 buffer layers, Diamond & Related Materials, 14, 314-317, 2005 [4] K.H. Lee, et al., Ir / SrTiO3 / Si multilayers: A promising substrate for diamond heteroepitaxy, International Conference on Diamond and Carbon Materials, YSA 1, 6-10 Sept. 2015 [5]N. Vaissière et al., Diamond and Related Materials, 36, 16-25, 2013