Aes, Leed, and UPS Studies of Fcc Iron Epitaxially Grown on COPPER(110) and COPPER(111)
AES, LEED, and, UPS were used to investigate the growth mode, diffusion effect, diffraction pattern, work function, and electronic structure of iron deposited on copper (100) and (111) surfaces. Initially iron grows epitaxially in the fcc structure in an almost layer-by -layer mode for the first 17 layers on the Cu(100) face and 4 ~ 5 layers on the Cu(111) surface. High coverages of iron result in the observation of a very faint LEED pattern infering the bcc iron formation on Cu(100). A p(2 x 2) diffraction pattern was observed from the carbon contaminated sample. High coverages of iron on the Cu(111) surface show a broad (1 times 1) hexagonal LEED pattern with satellites. This is due to the formation of bcc Fe(110) crystallites arranged in the domains with +/- 5 ^circ rotated orientations. Iron deposited on the copper single crystals diffuses into the substrate at high temperatures. LEED I/V measurements also show the diffusion effect at high temperatures. The work function for the clean Cu(100) was measured to be 4.9 eV and 5.5 eV for the 1 ML of fcc iron on the Cu(100). A measured work function for clean Cu(111) was 4.9 eV. We could hardly observe any changes of the work functions as a function of iron coverage on the Cu(111) surface. Iron deposited on Cu(100) at 190^ circC showed a splitting in the EDC spectra associated with a possible band splitting of the fcc iron. The CO is less reactive on the Fe/Cu(100) than on the Fe/Cu(111). We observed a clear 1pi + 5 sigma CO molecular orbital emission peak and a 4sigma molecular orbital energy peak from the iron on Cu(100) and Cu(111) after gas exposures of 60 L of CO at room temperature. We could not observe any evidence of ferromagnetism for fcc iron on a Cu(111) system at room temperature and at 100^circ C. After exposing the iron on Cu(111) sample to 60 L of CO gas at 100^circC we have observed a clear emission peak due to atomic carbon and oxygen instead of molecular CO orbital peak.
- Pub Date:
- Physics: Condensed Matter