Structure determination of the reconstructed Au(110) surface

Abstract

The LEED pattern of the Au( 110) surface shows a (1 X 2) and also a (1 X 3) superstructure.The (1 X 2) superstructure has been determined by comparison of LEED intensities with model calculations. The missing row model is the most probable model. A miniium of the averaged F-factor, F = 0.36, has been found for 15% contraction of the first layer spacing without atomic displacements in the second layer.The clean (110) faces of gold are known to exhibit a reconstruction of the atomic arrangement in the surface layers with respect to the bulk structure. Until now a (1 X 2) superstructure with a doubling of the lattice spacing in [OOI] direction has been reported [1,2] ; now also a (1 X 3) superstructure has been found. Characteristic for both structures are diffuse LEED beams, significantly broadened in [OOl] direction. The angular half width of the beams depends on energy and angle of incidence. This behaviour has been interpreted previously for the (1 X 2) superstructure, applying a disordered missing row model with a slightly roughened surface [2,3]. This model can be used as well to explain the existence of the (1 X 3) superstructure.Similar superstructures have been observed at the (110) faces of platinum and iridium [4] and a first structure analysis by LEED for Ir (1 lO)(l X 2) [S] shows, that the missing row model is the most probable one. Here we present a LEED structure determination, assuming a well-ordered superstructure, neglecting the effect of the disorder of the (110) surface.The Au crystal of 5N purity has been oriented within 0.5" of the [ 1 lo] direction by X-ray diffraction and was cut and planed by spark erosion. Electrochemical etching in SN HzS04 followed by electrolytical polishing in a cyanide solution produced a smooth reflecting surface. After argon ion bombardment the LEED pattern exhibits a very diffuse (1 X 2) superstructure -fig. la -which coalesces after tempering up to 800 K into the pattern of a (1 X 2) or (1 X 3) structure.The conditions at which the (1 X 3) superstructure appears are not quite clear; it seems to be dependent on the special ion bombardment conditions and probably on the cooling rate after tempering. In both cases the spots are broadened in [OOl] *

First-principles studies on clean and oxygen-adsorbed Ir(110) surfaces

“…II A͒, our calculations still indicate a preference for reconstruction, which is in agreement with experiments. [4][5][6][7][8][9][10]32,34 In these experiments it was also observed that at elevated temperatures and an oxygen partial pressure of 5 ϫ 10 −11 atm there is coexistence of different reconstructed surfaces. This is also supported by our calculations, since the stability of the three reconstructed surfaces differs only by 1 -3 meV/ Å 2 , which is within the inaccuracy of the calculations.…”

“…While 3d and 4d metals, such as Cu͑110͒, Ag͑110͒, or Pd͑110͒, preferentially reconstruct after adsorption of alkali metals ͑e.g., Na, K or Cs͒, [1][2][3] 5d metals, such as Au͑110͒, Pt͑110͒, or Ir͑110͒, reconstruct already in their clean states. [4][5][6][7][8][9][10] In contrast to clean Au͑110͒ and Pt͑110͒ surfaces, which show a ͑1 ϫ 2͒-missing-row reconstruction, [11][12][13][14][15][16][17] the situation is more complex for Ir͑110͒ and a variety of potential surface structures have been reported. Here the strong tendency towards stable ͕111͖ microfacets and nanofacets seems to be the driving force for different surface reconstructions, trying to minimize the overall surface free energy.…”

Multilayer distortion in the reconstructed (110) surface of Au

“…Though the previous structural results obtained by low energy electron diffraction (LEED) intensity analysis were somewhat unsatisfactory [3][4][5][6], a preference for the missing row model was always found. Most other models could be excluded by ion scattering studies [7][8][9][10][11].…”

“…The missing row model is consistent with the results of most other methods applied to the (110) faces of Pt, Ir and Au. All three faces are believed to exhibit the same reconstruction [3][4][5][6][7][8][9][10][11].…”

A Bayesian Approach to Surface X-ray Diffraction

“…The principal structural feature is that every other row of close-packed atoms along the 11 0 [ ] direction is missing, thereby doubling the unit cell in the 001 [ ] direction [22]. Also, this surface exhibits an oscillatory relaxation, with a contraction in the first-second layer spacing, and a slight expansion in the second-third layer spacing.…”