The adsorption of xenon on a ruthenium(10(1)over-bar-0) surface

The interaction of xenon with a ruthenium(1 0 1 0) surface was investigated between 29 and 300 K by means of low-energy electron diffraction (LEED), t emperature-programmed thermal desorption (TPD), and work function (Delta Ph i) measurements. TPD reveals a single desorption state at 135 K (coverage T heta = 0.01 ML) which shifts to lower temperatures as 0 increases and appea rs at 112 K for Theta = 0.78 ML. The initial desorption energy is 28.5 kJ/m ol and decreases with Theta; at Theta = 0.78 ML it is merely 20 kJ/mol. Bey ond this coverage there appears another, relatively sharp, desorption state at 88 K which is due to a phase transformation within the Xe monolayer. Fo r coverages 1 < Theta less than or equal to 1.35 ML, Xe desorbs via zero-or der kinetics, with a desorption energy of 17.5 kJ/mol. LEED reveals several phases with long-range order. At Theta = 0.5 ML, a (3 x 1) pattern, and at Theta = 0.78 ML, a (2 x 5) structure is observed. For 0.78 < 0 < 1 ML a qu asihexagonally, uniaxial commensurate (UC) structure is formed which consis ts of chains of Xe atoms with a mutual Xe-Xe distance of 4.2 (+/-0.1) Angst rom in [1210] direction. Work function measurements show a strong decrease even at small Xe coverages; at 0 = 0.78 ML, pronounced depolarization effec ts become effective, leading to a minimum of the Delta Phi(Theta)-curve nea r the monolayer coverage. At Theta = 1 ML, a Delta Phi of -1.29 eV is reach ed. The data are discussed and the results are compared with other noble ga s adsorption systems in view of the peculiar features, namely the clear evi dence of repulsive Xe-Xe interactions, the extraordinary large work functio n change, and the formation of a multilayer phase with square symmetry. (C) 2001 Elsevier Science B.V. All rights reserved.