ssp_10y - 3 Continued Surface crystallography Surface...

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3 Continued
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3-31 Surface crystallography Surface structure: periodic in 2 dimensions 3D lattice 2D lattice or net 5 Bravais nets in 2D (Figs. 2.1, 2.2) Unit cell mesh Substrate net of bulk crystal used as reference (Fig. 3.27); base vectors a 1 , a 2 Fig. 3.27. (a) Cube of an fcc lattice with faces of different orientation. (b-d) Top (open circles) and second layer (solid circles) of ideal fcc surfaces. The meshes of the substrate are indicated together with certain directions (as usual given in square brackets).
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3-32 Mesh of surface structure: c 1 , c 2 cP aP a a P a 1 11 1 12 2 2 21 1 22 2 = = + + c c P a a PP a a 1 2 1 2 11 12 21 22 1 2 = = Shorthand notation (due to E.A. Wood) for angle () aa 12 , = angle cc , : c a c a R 1 1 2 2 × α α : angle of relative rotation Superstructures Fig. 3.28. Examples of superstructures and their Wood notation. The c in figure b indicates a centered net. See also Figs. 3.24 and 3.25. Fig. 3.29. Description of positions of single adsorbed atoms in terms of their binding to substrate atoms. 22 3 33 0 ×× × ° cR
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3-33 2D reciprocal lattice 3D: ag i j =2 ij πδ 2D: cc i j * ij , i , j = 1,2 12 * , * : base in reciprocal lattice 3 rd dimension: 33 0 →∞⇒ * : quasi-continuous points rods Scattering condition: KG = Gh c k c l c c =++ * , ** * surface , Always reflexes also for monochromatic radiation!
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This note was uploaded on 01/19/2010 for the course MATERIALS M504 taught by Professor Adelung during the Spring '02 term at Uni Kiel.

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ssp_10y - 3 Continued Surface crystallography Surface...

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