Hh. Huang et al., THERMAL AND PHOTOINDUCED DESORPTION AND DECOMPOSITION OF FE(CO)(5) ONCLEAN AND OXYGEN-MODIFIED RU(001), Journal of physical chemistry, 100(46), 1996, pp. 18138-18144
The thermal and photoinduced desorption and decomposition of Fe(CO)(5)
on clean and O-covered Ru(001) surfaces were studied. Adsorption of F
e(CO)(5) on Ru(001) is associated with a partial decomposition, result
ing in the formation of CO and Fe(CO)(x) fragments. In the thermal des
orption spectrum for mass 28, the surface-stabilized decomposition pro
duct gives rise to a peak at 270 K, whereas the first and second monol
ayers of molecular Fe(CO)(5) desorb at 190 and 160 K, respectively. Th
e photochemical studies of Fe(CO)(5) at mono- and multilayered molecul
ar coverages on Ru(001) were carried out by UV irradiation at various
wavelengths (290-450 nm), Irradiation at wavelengths > 370 nm resulted
in photodesorption, while photodecomposition showed significant contr
ibution at shorter wavelengths. The total cross sections for the photo
chemical process closely follow the UV absorption spectrum of Fe(CO)(5
) in the gaseous phase, suggesting that the photoreaction is mainly du
e to the direct absorption of UV photons by the adsorbed Fe(CO)(5) mol
ecule. The photodecomposition yields reactive intermediates that subse
quently form Fe-x(CO)(y) clusters. These species thermally decompose,
desorbing the CO moieties and depositing Fe atoms on the surface. Diss
ociative adsorption of Fe(CO)(5) has also been observed on O-covered R
u(001). O adatoms create inhomogeneity in the adsorption sites for Fe(
CO)(5), as seen from the broadened desorption peak of the first molecu
larly adsorbed layer of Fe(CO)(5). In contrast to the clean surface, i
rradiation of Fe(CO)(5) adsorbed on O/Ru(001) at 290 nm produced relat
ively lower yields of photodecomposition and a higher extent of photod
esorption attributable to the more effective quenching of electronical
ly excited Fe(CO)(5) by the O-covered surface.