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Chlorine adsorption on copper
A296 Surface Science 131 (1983) 92-l 12 North-Holland Publishing Company
92
CHLORINE ADSORPTION ON COPPER I. Photoemission from clean Cu(OO1) and Cu(ll1) D. WESTPHAL and A. GOLDMANN Laboratorrum
fiir Festkdrperphyslk,
Unrversrtdt -GH
substrates
Dutsburg, D 4100 Duisburg I.
Fed. Rep. of German.) Received
4 March
1983; accepted
for publication
10 May 1983
As a first step to an understanding of the atomic chemisorption of Cl on Cu(OO1) and Cu( I1 1) we have studied high-resolution angle and photon-polarization dependent photoelectron spectra of the clean substrate surfaces. In a subsequent paper we will (besides presenting the energy dispersion curves of the adsorbate-derived bands) in particular discuss and interpret the adsorbate-induced changes within the substrate 3d-band emission spectra. Therefore a detailed understanding of the clean substrate emission was a necessary prerequisite. We demonstrate that a clear identification of bulk direct transitions, surface state emission and contributions from density of states transitions can be given. In particular we investigated the photoemission spectra from Cu(OO1) in the I’XWK bulk mirror plane excited by NeI, He1 and He11 radiation, from Cu(OO1) in the rXUL plane excited by He1 radiation, and from Cu( 111) along FLUX and I7LKL (HeI). The experimental bulk direct transitions are in very good agreement with simple calculations based on Burdick’s initial state band structure and a free electron like final state.
113
Surface Science 131 (1983) 113-138 North-Holland Publishing Company
CHLORINE ADSORPTION ON COPPER II. Photoemission from Cu(OOl)c(2 X 2)-Cl and Cu(lll)([s D. WESTPHAL
Laboratorrum fiir FestkGrperphysrk, Fed. Rep. of Germany Received
4 March
X
fi)R30”-Cl
and A. GOLDMANN
1983; accepted
Unrversitcit -GH for pubhcation
-D&burg,
D - 4100 Dursburg
1.
10 May 1983
We have studied high-resolution angle-resolved and photon-polarization dependent photoemission from chlorine adsorbed on Cu(OO1) and Cu( Ill). Chlorine forms a c(2 x 2) saturation overlayer on Cu(OO1) and adsorbs dissociatively as revealed by LEED and XPS. Several two-dimensional energy bands on Cu(OOl)c(2 X 2)-Cl could be identified and their dispersion behaviour along the r M and r X lines of the surface Brillouin zone, their respective mirror symmetry and their orbital character could be determined. An interpretation of these bands is given in terms of the interaction of the ordered overlayers with particular substrate bulk bands. Besides the appearance of adsorbate-induced two-dimensional bands drastic changes are resolved in the substrate d-band emission region. These can be explained almost exclusively by surface umklapp processes involving reciprocal lattice vectors of the ordered adsorbate mesh. Supplementary studies of the Cu( 111)(6 X fi)R30°-Cl system support our ideas. We discuss some important implications of our results for the interpretation of angle-resolved photoemission spectra from ordered adsorbate layers.
92
CHLORINE ADSORPTION ON COPPER I. Photoemission from clean Cu(OO1) and Cu(ll1) D. WESTPHAL and A. GOLDMANN Laboratorrum
fiir Festkdrperphyslk,
Unrversrtdt -GH
substrates
Dutsburg, D 4100 Duisburg I.
Fed. Rep. of German.) Received
4 March
1983; accepted
for publication
10 May 1983
As a first step to an understanding of the atomic chemisorption of Cl on Cu(OO1) and Cu( I1 1) we have studied high-resolution angle and photon-polarization dependent photoelectron spectra of the clean substrate surfaces. In a subsequent paper we will (besides presenting the energy dispersion curves of the adsorbate-derived bands) in particular discuss and interpret the adsorbate-induced changes within the substrate 3d-band emission spectra. Therefore a detailed understanding of the clean substrate emission was a necessary prerequisite. We demonstrate that a clear identification of bulk direct transitions, surface state emission and contributions from density of states transitions can be given. In particular we investigated the photoemission spectra from Cu(OO1) in the I’XWK bulk mirror plane excited by NeI, He1 and He11 radiation, from Cu(OO1) in the rXUL plane excited by He1 radiation, and from Cu( 111) along FLUX and I7LKL (HeI). The experimental bulk direct transitions are in very good agreement with simple calculations based on Burdick’s initial state band structure and a free electron like final state.
113
Surface Science 131 (1983) 113-138 North-Holland Publishing Company
CHLORINE ADSORPTION ON COPPER II. Photoemission from Cu(OOl)c(2 X 2)-Cl and Cu(lll)([s D. WESTPHAL
Laboratorrum fiir FestkGrperphysrk, Fed. Rep. of Germany Received
4 March
X
fi)R30”-Cl
and A. GOLDMANN
1983; accepted
Unrversitcit -GH for pubhcation
-D&burg,
D - 4100 Dursburg
1.
10 May 1983
We have studied high-resolution angle-resolved and photon-polarization dependent photoemission from chlorine adsorbed on Cu(OO1) and Cu( Ill). Chlorine forms a c(2 x 2) saturation overlayer on Cu(OO1) and adsorbs dissociatively as revealed by LEED and XPS. Several two-dimensional energy bands on Cu(OOl)c(2 X 2)-Cl could be identified and their dispersion behaviour along the r M and r X lines of the surface Brillouin zone, their respective mirror symmetry and their orbital character could be determined. An interpretation of these bands is given in terms of the interaction of the ordered overlayers with particular substrate bulk bands. Besides the appearance of adsorbate-induced two-dimensional bands drastic changes are resolved in the substrate d-band emission region. These can be explained almost exclusively by surface umklapp processes involving reciprocal lattice vectors of the ordered adsorbate mesh. Supplementary studies of the Cu( 111)(6 X fi)R30°-Cl system support our ideas. We discuss some important implications of our results for the interpretation of angle-resolved photoemission spectra from ordered adsorbate layers.