2-DIMENSIONAL PHASE-TRANSITION OF ADSORBED XENON ON NIAL(110) AND AL(110)

The Xe adsorption on NiAl(110) and Al(110) has been studied at 45 K by ultraviolet photoelectron spectroscopy (UPS), thermal desorption spectroscopy (TDS) and low-energy electron diffraction (LEED). On both surfaces a two-dimensional (2D) Xe Gas-2D Xe solid phase transition is observed. On NiAl(110) this 2D-phase transition occurs at THETA-(Xe) almost-equal-to 0.3 monolayer (ML) as judged by UPS and TDS. A Xe induced LEED pattern suggesting long range order, however, is only observed beyond THETA-(Xe) almost-equal-to 0.5 ML. On Al(110) the 2D Xe condensation occurs already at a coverage of THETA-(Xe) almost-equal-to 0.1 ML, most likely within the troughs, because the Xe induced LEED pattern exhibits the same periodicity (perpendicular to the surface troughs) as the Al(110) substrate.