Investigation of the adsorption and decomposition of Fe(CO)5 on fcc and bcc iron films by infrared reflection absorption spectroscopy

The adsorption and decomposition of Fe(CO)5 on fcc and bcc iron films at 90 K were investigated using infrared reflection absorption spectroscopy (IRRAS). The fcc film was epitaxially grown on a Cu(1 0 0) crystal at room temperature, whereas the bcc film was deposited as polycrystalline by electron-beam evaporation onto a Si(1 1 1) wafer. The saturated adsorption of Fe(CO)5 on the fcc Fe(1 0 0) surface yielded a dominant IRRAS band at 2060 cm−1 due to the axial CO stretch mode of Fe(CO)5. Upon UV (254 nm) irradiation to the adsorbed layer, the 2060 cm−1 band decreased in intensity and a new band appeared at 2072 cm−1, indicating the photolytic decomposition of the adsorbed Fe(CO)5. Fe(CO)5 adsorption on the polycrystalline bcc surface gave rise to a single intense band at 2072 cm−1 which was not changed in position by UV irradiation. We conclude from these results that the fcc(1 0 0) surface is inactive for the decomposition of Fe(CO)5 in comparison to the polycrystalline bcc surface.