N. Nilius et al., LOW-TEMPERATURE SCANNING-TUNNELING-MICROSCOPY STUDY OF O-2 ADSORPTIONON RU(0001), Applied physics A: Materials science & processing, 66, 1998, pp. 519-523
The adsorption process of O-2 on Ru(0001) has been studied in the temp
erature range between 100 K and 300 K by means of low-temperature scan
ning tunnelling microscopy (STM). At temperatures below 130 K the exis
tence of a molecular precursor state leads to the formation of dense,
disordered islands (partly with a (1 x 1) configuration). Between 160
K and 170 K the onset of diffusion of the chemisorbed O atoms allows a
local ordering process in the adsorbate layer. Above 210 K the system
reaches a well-ordered equilibrium state, formed by (2 x 2) and (2 x
1) structures. From the analysis of the island density versus adsorpti
on temperature data the diffusion energy for the physisorbed precursor
state is estimated.