Initial stages of oxide formation on the Zr surface at low oxygen pressure: An in situ FIM and XPS study.

An improved methodology of the Zr specimen preparation was developed which allows fabrication of stable Zr nanotips suitable for FIM and AP applications. Initial oxidation of the Zr surface was studied on a Zr nanotip by FIM and on a polycrystalline Zr foil by XPS, both at low oxygen pressure (10(-8)-10(-7)mbar). The XPS data reveal that in a first, fast stage of oxidation, a Zr suboxide interlayer is formed which contains three suboxide components (Zr(+1), Zr(+2) and Zr(+3)) and is located between the Zr surface and a stoichiometric ZrO2 overlayer that grows in a second, slow oxidation stage.

High-field versus high-pressure: weakly adsorbed CO species on Pt(111).

Adsorption of carbon monoxide on a nanosized apex facet of a [111]-oriented Pt field emitter tip was studied under high electrostatic field conditions (15-20V/nm) by field ion appearance energy spectroscopy (FIAES). Weakly bound highly mobile CO species have been detected and their possible role in surface reactions such as CO oxidation on Pt was elucidated. The FIAES results are compared with those of vibrational sum frequency generation (SFG) spectroscopy of CO adsorption on a macroscopic Pt(111) single crystal, in a gas pressure range from UHV to atmospheric.