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- CHAKARIAN, V, et al.
(författare)
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THE ADSORPTION OF I2 ON SI(111)-7X7 STUDIED BY SOFT-X-RAY PHOTOEMISSION
- 1993
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Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 296:3, s. 383-392
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Tidskriftsartikel (refereegranskat)abstract
- The adsorption Of I2 on Si(111)-7 x 7 at room temperature is studied with soft X-ray photoelectron spectroscopy. I2 adsorbs dissociatively, forming a mixture of SiI, SiI2 and SiI3 moieties, of which SiI dominates. The Fermi level is pinned near mid-gap, moving slightly towards the conduction band as the I coverage increases. The surface work function increases monotonically with I coverage. The I 4d core-level displays a single chemical state, which decreases in binding energy with increasing coverage. Analysis of the Si 2p core-level spectra shows that the adsorption proceeds first by attachment of I to the dangling bonds of the 7 x 7 unit cell and that, at saturation, 1.57 +/- 0.05 ML of I atoms are adsorbed in 1.10 +/- 0.02 ML of SiI(x) groups. These results indicate that substrate Si-Si bonds are broken by reaction with I2. The total I coverage is limited, however, by the availability Of surface dangling bonds that are required to initiate the dissociation Of I2 molecules.
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| 4. |
- HIMPSEL, FJ, et al.
(författare)
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DIELECTRICS ON SEMICONDUCTORS
- 1988
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Ingår i: Materials Science & Engineering. - : Elsevier BV. - 0921-5107 .- 1873-4944. ; 1:1, s. 9-13
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Tidskriftsartikel (refereegranskat)
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| 5. |
- HIMPSEL, FJ, et al.
(författare)
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FINE-STRUCTURE OF THE CA 2P X-RAY-ABSORPTION EDGE FOR BULK COMPOUNDS, SURFACES, AND INTERFACES
- 1991
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 43:9, s. 6899-6907
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Tidskriftsartikel (refereegranskat)abstract
- The fine structure of the Ca 2p soft-x-ray-absorption edge is studied for a variety of bulk compounds (Ca metal, CaSi2, CaO, and CaF2), for surfaces and interfaces [CaF2(111), BaF2 on CaF2(111), Ca and CaF2 on Si(111)], and for defects (F centers in CaF2). The observed multiplet structure is explained by atomic calculations in a crystal field [cubic O(h) for the bulk and threefold C3-nu for the (111) surfaces and interfaces]. While the bulk spectra are isotropic, the surface and interface spectra exhibit a pronounced polarization dependence, which is borne out by the calculations. This effect can be used to become surface and/or interface selective via polarization-modulation experiments, even for buried interfaces. A change in valence from Ca2+ to Ca1+ causes a downwards energy shift and extra multiplet lines according to the calculation. The energy shift is observed for F centers at the CaF2 surface and for the CaF2/Si(111) interface.
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