@article {5117, title = {Tensor LEED analysis for the electrodeposited Pt(111)-(3x3)-Ag,I surface structure}, journal = {Surface Science}, volume = {490}, number = {3}, year = {2001}, note = {ISI Document Delivery No.: 473XWTimes Cited: 5Cited Reference Count: 34}, month = {Sep}, pages = {256-264}, type = {Article}, abstract = {A crystallographic analysis is reported using low-energy electron diffraction (LEED) in the tensor LEED approach for the electrodeposited coadsorption (3 x 3) structure with 4/9 monolayer (ML) of silver and 4/9 ML of iodine on the Pt(1 1 1) surface. The structure approximates a two-layer slice of bulk AgI cut parallel to its (1 1 1) plane and superimposed on the substrate with the Ag atoms in contact with the topmost Pt(1 1 1) layer, and the I atoms forming an overlayer on the Ag atoms. There are two types of Ag atoms in the (3 x 3) unit mesh; one type bonds to a single Pt atom, while the other type bonds to three Pt atoms. The average Ag-Pt bond distances are close to 2.48 and 2.82 (A) over circle respectively for the one and three-coordinate Ag atoms, but both types of Ag atoms bond to three I atoms with an average Ag-I distance of 2.67 (A) over circle. No significant corrugation is observed for either the I layer or the Ag layer. (C) 2001 Elsevier Science B.V. All rights reserved.}, keywords = {ADSORBATES, ADSORPTION, AG, chemisorption, ELECTROCHEMISTRY, ENERGY-ELECTRON-DIFFRACTION, IODINE, LOW ENERGY ELECTRON DIFFRACTION (LEED), METAL-SURFACES, platinum, PT(111), SCANNING-TUNNELING-MICROSCOPY, silver}, isbn = {0039-6028}, url = {://000171075300007}, author = {Labayen, M. and Harrington, D. A. and Saidy, M. and Mitchell, K. A. R.} } @article {3857, title = {Tensor LEED analyses for the (root 3x root 3)R30 degrees and c(4x2) structures formed by sulphur chemisorbed on the (111) surface of rhodium}, journal = {Surface Science}, volume = {345}, number = {1-2}, year = {1996}, note = {ISI Document Delivery No.: TT592Times Cited: 17Cited Reference Count: 16}, month = {Jan}, pages = {101-109}, type = {Article}, abstract = {Tensor LEED analyses have been made for the Rh(111)-(root 3 x root 3)R30 degrees-S and Rh(lll)-c(4 x 2)-S surface structures formed by S chemisorbed at 1/3 and 1/2 monolayer coverages respectively. For the lower-coverage form, S adsorbs on the regular three-coordinate sites which continue the fee packing sequence; the S-Rh bond lengths are indicated to equal 2.23 Angstrom, and relaxations in the metallic structure are negligible. In the c(4 x 2) form, the adsorption occurs equally on both types of three-coordinate site (fee and hcp), although some surface Rh atoms bond to two S atoms while others bond to just one, and this sets up some interesting relaxations. Specifically, the S atoms displace laterally from the centre of the three-fold sites by 0.20 to 0.29 Angstrom, and the first metal layer is buckled by about 0.23 Angstrom. The first-to-second interlayer spacing in the metal expands to 2.26 Angstrom from the bulk value of 2.20 Angstrom. The average S-Rh bond lengths equal 2.22 Angstrom, and so they are not significantly changed from that in the low-coverage form. The structural evolution for S chemisorbed on the (111) surface of rhodium with increasing coverage is compared with the corresponding evolution on the Rh(110) surface.}, keywords = {ABSORPTION FINE-STRUCTURE, ASSIGNMENT, chalcogens, CRYSTAL SURFACES, HOLLOW ADSORPTION SITE, LOW ENERGY ELECTRON DIFFRACTION (LEED), LOW INDEX SINGLE, NI(111), NO, rhodium, SURFACE RELAXATION}, isbn = {0039-6028}, url = {://A1996TT59200014}, author = {Wong, K. C. and Liu, W. and Saidy, M. and Mitchell, K. A. R.} } @article {3546, title = {LEED ANALYSES REVISITED FOR 2 STRUCTURES FORMED BY ZR(0001) - THE SURFACE WHEN CLEAN AND WHEN CONTAINING SUFFICIENT OXYGEN TO JUST EXTINGUISH THE HALF-ORDER BEAMS}, journal = {Surface Science}, volume = {343}, number = {1-2}, year = {1995}, note = {ISI Document Delivery No.: TK128Times Cited: 26Cited Reference Count: 22}, month = {Dec}, pages = {L1167-L1173}, type = {Letter}, abstract = {LEED crystallographic analyses have been made for two structures formed by the (0001) surface of zirconium and which show (1 x 1)-type diffraction patterns. An analysis with eight diffracted beams for clean Zr(0001) supports an earlier conclusion that this surface has a regular hcp-type structure, and that the first interlayer spacing shows a contraction hem the bulk spacing by about 1.6\%. A surface formed by O, at twice the coverage applying for the best-developed half-monolayer (2x2) diffraction pattern, is analyzed using tensor LEED for nine diffracted beams, including the use of the average t-matrix approximation. It is concluded that the 1 monolayer (ML) structure is actually disordered with 0.5 ML of O distributed statistically over octahedral holes between the first and second Zr layers, and another 0.5 ML of O similarily distributed between the second and third metal layers.}, keywords = {CRYSTALLOGRAPHIC INVESTIGATIONS, ENERGY-ELECTRON-DIFFRACTION, LOW ENERGY ELECTRON DIFFRACTION (LEED), LOW INDEX SINGLE CRYSTAL, OXYGEN, SANDWICH, SURFACE RELAXATION AND RECONSTRUCTION, SURFACES, ZIRCONIUM}, isbn = {0039-6028}, url = {://A1995TK12800004}, author = {Wang, Y. M. and Li, Y. S. and Mitchell, K. A. R.} } @article {3547, title = {A LEED CRYSTALLOGRAPHIC ANALYSIS FOR THE HALF MONOLAYER STRUCTURE FORMED BY O AT THE ZR(0001) SURFACE}, journal = {Surface Science}, volume = {342}, number = {1-3}, year = {1995}, note = {ISI Document Delivery No.: TH886Times Cited: 32Cited Reference Count: 35}, month = {Nov}, pages = {272-280}, type = {Article}, abstract = {A tensor LEED analysis has been made for the half monolayer structure formed by O absorbed at the Zr(0001) surface. The analysis uses intensity-versus-energy curves for eight independent diffracted beams measured at normal incidence. The best correspondence with the experimental intensity data is for a model in which O atoms occupy octahedral holes in an unreconstructed metallic structure, with 0.25 ML between the first and second metal layers, and another 0.25 ML between the second and third metal layers. These two (2 X 2)-O arrays are displaced laterally from one another by an unit translational vector of the Zr(0001) substrate. The O atoms induce both vertical and lateral relaxations in the three topmost Zr layers; the largest displacements being found in the second Zr layer. The averaged O-Zr bond length is 2.28 Angstrom, about 0.02 Angstrom shorter than the value in bulk ZrO.}, keywords = {0001 SURFACE, 2)-O, ALPHA-AL2O3, chemisorption, ENERGY-ELECTRON-DIFFRACTION, INDUCED RECONSTRUCTION, LOW ENERGY ELECTRON DIFFRACTION (LEED), LOW INDEX SINGLE CRYSTAL, OXIDATION, OXYGEN, SURFACE RELAXATION, SURFACES, X, ZIRCONIUM}, isbn = {0039-6028}, url = {://A1995TH88600034}, author = {Wang, Y. M. and Li, Y. S. and Mitchell, K. A. R.} } @article {3488, title = {A STRUCTURAL STUDY OF PD/CU(100) SURFACE ALLOYS}, journal = {Surface Science}, volume = {337}, number = {1-2}, year = {1995}, note = {ISI Document Delivery No.: RQ749Times Cited: 33Cited Reference Count: 54}, month = {Aug}, pages = {79-91}, type = {Article}, abstract = {The structures formed by one-half and one monolayer (ML) of Pd evaporated onto Cu(100) at 300 K were studied by low energy electron diffraction (LEED), medium energy ion scattering (MEIS), thermal desorption spectroscopy (TDS), and embedded atom method (EAM) calculations. In the half monolayer case, the LEED I(E) curves are consistent with the established c(2 x 2) surface alloy model. The MEIS data, however, suggest that a fraction of the Pd (similar to 1/4) is in {\textquoteright}{\textquoteright}second layer{\textquoteright}{\textquoteright} sites, in agreement with previous LEIS, TDS and XPS forward scattering measurements. The EAM simulations support the formation of alloy islands, providing a mechanism for the covering of some Pd atoms. As the deposition proceeds, however, this island formation is indicated to occur preferentially over clean copper. In the one monolayer case, a p(2 x 2)-p4g LEED pattern is observed. Analysis of the I(E) curves suggests that this arises from (100) Pd packed above the c(2 x 2) alloy. EAM calculations confirm the stability of this model. Evidence from MEIS and TDS, however, shows that the one monolayer surface as prepared in this work is inhomogeneous. c(2 x 2) and Cu rich surface domains exist in addition to those having the p4g Pd/c(2 x 2)PdCu structure.}, keywords = {(MEIS), ABSORPTION FINE-STRUCTURE, ADSORPTION, CU(100), DIFFRACTION, GROWTH, HYDROGEN, ION-SCATTERING, LOW ENERGY ELECTRON DIFFRACTION (LEED), LOW-ENERGY ELECTRON, MEDIUM ENERGY ION SCATTERING, molecular dynamics, RECONSTRUCTION, SPECTROSCOPY, surface structure, THERMAL DESORPTION, ULTRATHIN PD FILMS}, isbn = {0039-6028}, url = {://A1995RQ74900017}, author = {Pope, T. D. and Vos, M. and Tang, H. T. and Griffiths, K. and Mitchell, I. V. and Norton, P. R. and Liu, W. and Li, Y. S. and Mitchell, K. A. R. and Tian, Z. J. and Black, J. E.} } @article {3559, title = {Tensor LEED analysis for the Rh(110)-(3x2)-S surface structure}, journal = {Surface Science}, volume = {344}, number = {3}, year = {1995}, note = {ISI Document Delivery No.: TQ239Times Cited: 6Cited Reference Count: 26}, month = {Dec}, pages = {258-266}, type = {Article}, abstract = {A tensor LEED analysis for the Rh(110)-(3 x 2)-S surface supports an arrangement of chemisorbed S atoms at 2/3 monolayer coverage on a basically unreconstructed metallic structure. Alternating [1(1) over bar0$] channels in the metal surface are occupied differently, although each has two S atoms per unit mesh. In one set, the S atoms occupy long-bridge and centre sites with a constant separation along the channel of 4.03 Angstrom. In the other set of channels, all S atoms occupy equivalent positions, displaced from regular centre sites by 0.39 Angstrom, to give successive S to S separations of 3.47 and 4.60 Angstrom. The long-bridge site bonding is a novel feature which is facilitated by the neighbouring topmost Rh atoms relaxing laterally by about 0.27 Angstrom perpendicular to the [1(1) over bar0$] row. Bucklings of 0.20 and 0.10 Angstrom are indicated to occur in the first and second Rh layers respectively; the latter value essentially equals that (0.11 Angstrom) reported earlier for the corresponding half monolayer c(2 x 2) surface. For S atoms at or near centre sites in the (3 x 2) structure, the average S-Rh bond distances are 2.42 and 2.29 Angstrom to the first and second layer Rh atoms respectively; the corresponding values at the long-bridge sites are 2.20 and 2.27 Angstrom.}, keywords = {chalcogens, chemisorption, CRYSTAL SURFACES, ENERGY-ELECTRON-DIFFRACTION, GENERAL TRENDS, LOW ENERGY ELECTRON DIFFRACTION (LEED), LOW INDEX SINGLE, rhodium, SULFUR ADSORPTION, SURFACE RELAXATION AND RECONSTRUCTION}, isbn = {0039-6028}, url = {://A1995TQ23900020}, author = {Wong, K. C. and Liu, W. and Mitchell, K. A. R.} }