Ultrathin cerium oxide films have been prepared by oxidizing Ce-Pt/Pt(111) surface alloys with 65 L O(2) at 900 K. According to low electron energy diffraction data, phonon spectra recorded by high resolution electron energy loss spectroscopy and scanning tunneling microscopy measurements the films are of fluorite-type CeO(2)(111) structure. They grow three dimensionally as islands, which are flat and up to several hundred square nanometers large. The film thickness varies between one and five layers. The band gap of the oxide films has been probed by scanning tunneling spectroscopy and turned out to be significantly smaller than for bulk CeO(2). (C) 2011 Elsevier B.V. All rights reserved.