Metal particles of Pt, Ni, Au and Ag, typically less than 50 Å in diameter, were deposited by vacuum evaporation onto substrates of ultrathin (∼25 Å) SiO2 on Si. The particle size and charge were determined by transmission electron microscopy and MOS type capacitance-voltage measurements, respectively. It was observed that the Pt and Ni particles were smaller and more closely spaced than Au and Ag particles under comparable deposition conditions. The particle charge for Pt and Ni appeared to exceed that for Au and Ag for the same substrate coverage, suggesting possible charge contributions to heterogeneous nucleation. Since Pt and Ni particles were observed to carry a positive charge, they are presumably stabilized at negative substrate sites; the opposite appears to be true for Au and Ag. © 1974.