Ir nanoislands were electrodeposited from chloride solutions on n-type Si(111) surfaces. The conditioned surface was investigated by electrochemical capacitance measurements, ex situ atomic force microscopy, high resolution transmission electron microscopy, and in-system synchrotron radiation photoelectron spectroscopy (SRPES). The growth of metal particles was accompanied by the formation of an ultrathin oxide layer, conforming to nanodimensioned metal-oxide-semiconductor (MOS) junctions. SRPES Si core-level spectra obtained with surface-sensitive excitation energies show the presence of a SiO2 signal with 30-40% of the oxide signal contribution arising from intermediate oxidation states Si+, Si2+, and Si3+. The valence band spectrum reveals that the Fermi level of silicon is pinned at the gap states of the Si-SiO2 interface at 0.6 eV above the valence band, driving the semiconductor under depletion. The presence of metal particles induces a lateral modulation of the interfacial electric field by the formation of nanoscaled MOS junctions with a Schottky barrier of 0.84 eV, as assumed by extrapolating the behavior of full-covered solid-state MOS junctions.