LOCAL TOPOGRAPHY AND ENERGY NONUNIFORMITY OF THE SINGLE-CRYSTAL AND TEXTURED PLATINUM SURFACES STUDIED BY THE ELECTROCHEMICAL SCANNING-TUNNELING-MICROSCOPY AND SPECTROSCOPY

Surfaces of platinum electrodes in 0.05 M H2SO4 are studied. In situ s canning tunneling microscopy (STM) images of oriented single-crystal f aces (111), (110), and (311) of platinum and those of textured platinu m coatings are obtained in the potential region 0.3 to 1.7 V. Scanning tunneling spectroscopy (STS) is used to measure a series of spectra, i.e., dependences of the tunneling current on the tunneling voltage an d the tunneling gap at the Pt electrode potentials in the intervals 0. 1-1.3 and 0.46-1.2 V, respectively. The STM and STS data, obtained at different modes of imposing the potential and scanning the samples, ar e analyzed. For the Pt(111) face, potentials at which the shape of the tunneling potential barrier alters and the barrier's effective height are estimated. It is discovered that the latter doubles upon raising the Pt(111) potential from 0.7 to 1.2 V. An essential local inhomogene ity of the Pt electrodes is found, which depends on both the potential of single-crystal samples studied and the face type.