Structure of Al/Si(111) Interfaces - a Photoemission Extended X-Ray-Absorption Fine-Structure Study
The atomic geometries of Al/Si(111) interfaces for 1.1 and 2.2 monolayer (ML) aluminum coverages at room temperature have been determined by photoemission extended x-ray-absorption fine structure (PEXAFS). The clean Si(111) surface was prepared by vacuum cleaving, which is known to have a (2 x 1) reconstruction. For 1.1 and 2.2 ML Al/Si(111) interfaces, Si 2p and Al 2p PEXAFS data were acquired. The data were analyzed by Fourier analysis and curve-fitting procedures using the theoretical backscattering phase function of McKale et al. plus absorber phase function of Teo and Lee. For the clean Si(111)-(2 x 1) surface, the first Si-Si bond length is determined as 2.40 +/- 0.04 angstrom, which is slightly larger than its bulk value (2.35 angstrom). For Al/Si(111) interfaces, the average of Si-Si and Si-Al nearest-neighbor distances was determined as 2.47 +/- 0.04 angstrom from the Si 2p PEXAFS. For the 1.1 ML Al/Si(111) interface, the nearest-neighbor Al-Si bond length, derived from Al 2p PEXAFS, is 2.49 +/- 0.04 angstrom, which interface, the nearest-neighbor Al-Si bond length, derived from Al 2p PEXAFS, is 2.49 +/- 0.04 angstrom, which is in excellent agreement with the Al-Si bond length for the Al/Si(111)-(square-root 3 x square-root 3) interface as reported in the literature. For the 2.2 ML Al/Si(111) interface, Al 2p PEXAFS yielded an Al-Al bond length of 2.94 +/- 0.05 angstrom, which is close to its value in Al metal.
WOS:A1991GH55300033
1991
44
12
6284
6290
Univ notre dame,dept elect engn,notre dame,in 46556. univ wisconsin madison,ctr synchrotron radiat,stoughton,wi 53589. univ wisconsin madison,dept phys,stoughton,wi 53589. ecole polytech fed lausanne,inst phys appl,ph ecublens,ch-1015 lausanne,switzerland.
ISI Document Delivery No.: GH553
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