Surface structure determinations of ordered sulfur overlayers on Mo(100) and Re(0001) by low-energy electron diffraction intensity analysis
- Univ. of California, Berkeley, CA (United States)
A newly developed method for surface structure determination, tensor LEED, combined with automated search was used to analyze the structures. The ordered structures of S on Mo(100) which were studied formed a c(2 x 2), c(4 x 2), and p(2 x l) periodicities at coverages of 0.5, 0.75, 1.0 ML (monolayers, of one sulfur atom per one molybdenum atom) respectively. A MO2S-like overlayer, which formed at coverages greater than 1.0 ML, is also discussed. Calculations for the c(2 x 2) structure gave a best fit geometry with S adsorbed in a four-fold symmetric hollow site and the second layer buckled by 0.09Å. The S-Mo bond length is 2.45Å and the Pendry R-factor is 0.21. Preliminary calculations for the c(4 x 2) structure did not yield an acceptable fit. The three models tried are discussed. Calculations for p(2 x l) data did not yield an acceptable geometry either. The types of models that were tried are discussed. Implications of this analysis are discussed along with results of a scanning tunneling microscopy (STM) investigation. The ordered structures on the RE(0001) surface studied have p(2 x2) and (2√3 x 2√3)R30° periodicities and occurred at S coverages of 0.25 and 0.5 ML respectively. Best fit structure for p(2 x 2) structure has S adsorbed in a three-fold hollow hcp site and exhibits a buckling of the first and second Re layers. The first layer is buckled by 0.05Å and the second layer is buckled by 0.06Å. Re-S bond length is 2.32Å and Pendry R-factor is 0.21. Preliminary results of dynamical LEED investigation of (2√3 x 2√3)R30° structure show reasonable agreement with a model with a 6-S atom basis.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 10186839
- Report Number(s):
- LBL-33514; ON: DE94001250
- Resource Relation:
- Other Information: TH: Thesis (Ph.D.); PBD: Nov 1992
- Country of Publication:
- United States
- Language:
- English
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