STRUCTURE AND COMPLETE CHEMICAL PASSIVATION OF PT(997)

We report on scanning tunneling microscopy and infrared reflection abs orption spectroscopy investigations of the steppe Pt(997) surface. The surface shows a regular terrace-step-structure with only moderate var iations of the terrace widths with respect to the nominal structure. T he adsorption of CO as well as the coadsorption of hydrogen and CO is studied. It is shown that covering the surface with a full monolayer o f hydrogen at 165 K provides its complete passivation against adsorpti on from the residual gas atmosphere, without affecting the terrace-ste p-configuration. Thus the surface can be kept clean in UHV over months , a necessary precondition to serve as diffractive element in atom bea m optics.