Ultrathin silica films with different thicknesses have been gown on a Pd(100) surface by depositing silicon in the presence Of O-2. The film composition and electronic properties were characterized by X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), and high-resolution electron energy loss spectroscopy (HREELS). Scanning tunneling microscopy was applied to investigate the film morphology and lattice structure. The results show that the obtained films are atomically flat and highly ordered in a long range. UPS and HREELS measurements indicate that the silica film has the same electronic and vibrational properties as bulk silica. A 2.8 nm thick film exhibits low defects in the film and high thermal stability up to 800 K, as evidenced by ion scattering spectroscopy and XPS. (c) 2007 Elsevier B.V. All rights reserved.