HELIUM DIFFRACTION ANALYSIS OF THE MICROFACETED IR(110) SURFACE

A new reconstruction of the iridium (110) surface has been characterized using helium atom diffraction, low-energy electron diffraction, and Auger electron spectroscopy. Our observations are consistent with a surface composed primarily of <331> and <331BAR> microfacets, which are roughly 18 angstrom wide in the direction perpendicular to the close-packed rows of atoms and much longer in the direction parallel to the rows. Traces of oxygen or other surface impurities appear to be important in determining the structure of the Ir(110) surface. This sensitivity to surface composition, together with the unique geometry of the microfaceted surface, raises questions about the electronic forces that determine the arrangements of surface atoms.