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Angle resolved photoemission study of the c(2×2)Si overlayer on Fe(100)
A201 Surface
388
Sctence 141 (1984) 388-396 North-Holland. Amsterdam
A KINETIC MODEL FOR ISOTHERMAL COVERAGE OF CHARGED SPECIES ON FILM SURFACES R. HUZIMURA, K. MATSUMURA and S. YAMANAKA Naro
Umuersity of Education,
Received
17 January
OSCILLATIONS
Nara 630, Japan
1984; accepted
for publication
13 March
1984
Through kinetic equation studies we find that coverages of adsorbed or trapped charged species on two surfaces on a film separating and facing two spaces can show oscillations at a constant temperature without assuming the Langmuir-Hinshelwood type process. Instead it is required that at least one of the activation energies for their thermal release has the form of an increasing function of the coverage; the coefficient representing annihilation of adsorbates through tunneling or recombination and that representing reduction of adsorbing rate by a coverage effect are not zero. The changes of oscillatory aspects with some kinetic parameters are examined and a significant temperature dependence of the oscillation is found.
39-l
Surface Science 141 (1984) 397-408 North-Holland, Amsterdam
ANGLE RESOLVED PHOTOEMISSION OVERLAYER ON Fe(100) B. EGERT * and H.J. GRABKE
STUDY OF THE c(2 x 2)Si
&fax Planck Instrtut ftir Eisenforschung GmbH, D - 4000 Diisseldorf I, Fed. Rep. of Germany and Y. SAKISAKA ** and T.N. RHODIN School of Applied and Engineering Physics and Materials Science Center, Cornell University, Ithaca, New York 14853, USA Received 27 December 1983; accepted for publication 12 March 1984
Angle resolved photoemission experiments utilizing polarized synchrotron radiation were performed to study the electronic structure of valence levels of Si segregated in a c(2 x 2) overlayer on the a-Fe(100) surface. The spectra were taken at varying photon energies (14 I Aw I 40 eV), in dependence on the polarization of the incoming light, and as a function of the photoelectron emission angle in the symmetry directions rM’ and rX’ of the surface Brillouin zone. Evaluation of the photoemission data shows that the Si 3p levels form energy bands for the ordered c(2 x 2) overlayer on Fe(100). The initial state energy of the Si 3p states depends on k ,, being measured. At r a bonding Si 3p, state (a, symmetry) and an antibonding Si 3p,& state (e symmetry) is analyzed, which are separated by 0.8 eV in binding energy. In going from r to M’ the Si 3p, induced level disperses - 0.8 eV to lower initial state energies. In the Txf direction the overall Si 3p band width is approximate 1.3 eV. Though the interaction between silicon and iron surface atoms are relatively weak compared to Fe(lOO)-~(2x2)s. modifications in the Fe derived valence band states occur, including the formation of a hybridization state located 1.4 eV below E,.
388
Sctence 141 (1984) 388-396 North-Holland. Amsterdam
A KINETIC MODEL FOR ISOTHERMAL COVERAGE OF CHARGED SPECIES ON FILM SURFACES R. HUZIMURA, K. MATSUMURA and S. YAMANAKA Naro
Umuersity of Education,
Received
17 January
OSCILLATIONS
Nara 630, Japan
1984; accepted
for publication
13 March
1984
Through kinetic equation studies we find that coverages of adsorbed or trapped charged species on two surfaces on a film separating and facing two spaces can show oscillations at a constant temperature without assuming the Langmuir-Hinshelwood type process. Instead it is required that at least one of the activation energies for their thermal release has the form of an increasing function of the coverage; the coefficient representing annihilation of adsorbates through tunneling or recombination and that representing reduction of adsorbing rate by a coverage effect are not zero. The changes of oscillatory aspects with some kinetic parameters are examined and a significant temperature dependence of the oscillation is found.
39-l
Surface Science 141 (1984) 397-408 North-Holland, Amsterdam
ANGLE RESOLVED PHOTOEMISSION OVERLAYER ON Fe(100) B. EGERT * and H.J. GRABKE
STUDY OF THE c(2 x 2)Si
&fax Planck Instrtut ftir Eisenforschung GmbH, D - 4000 Diisseldorf I, Fed. Rep. of Germany and Y. SAKISAKA ** and T.N. RHODIN School of Applied and Engineering Physics and Materials Science Center, Cornell University, Ithaca, New York 14853, USA Received 27 December 1983; accepted for publication 12 March 1984
Angle resolved photoemission experiments utilizing polarized synchrotron radiation were performed to study the electronic structure of valence levels of Si segregated in a c(2 x 2) overlayer on the a-Fe(100) surface. The spectra were taken at varying photon energies (14 I Aw I 40 eV), in dependence on the polarization of the incoming light, and as a function of the photoelectron emission angle in the symmetry directions rM’ and rX’ of the surface Brillouin zone. Evaluation of the photoemission data shows that the Si 3p levels form energy bands for the ordered c(2 x 2) overlayer on Fe(100). The initial state energy of the Si 3p states depends on k ,, being measured. At r a bonding Si 3p, state (a, symmetry) and an antibonding Si 3p,& state (e symmetry) is analyzed, which are separated by 0.8 eV in binding energy. In going from r to M’ the Si 3p, induced level disperses - 0.8 eV to lower initial state energies. In the Txf direction the overall Si 3p band width is approximate 1.3 eV. Though the interaction between silicon and iron surface atoms are relatively weak compared to Fe(lOO)-~(2x2)s. modifications in the Fe derived valence band states occur, including the formation of a hybridization state located 1.4 eV below E,.