The structure of the clean Co(1010) surface has been analysed by LEED. Application of a recently developed computational scheme reveals the prevalence of the termination A in which the two topmost layers exhibit a narrow spacing of 0.62 A, corresponding to a 12.8( + 0.5)% contraction with respect to the bulk value, while the spacing between the second and third layer is slightly expanded by 0.8( + 0.2)%.The (1010) surface of a hcp crystal represents the counterpart to the well-known (110) plane of fcc crystals. In contrast to the latter, however, so far only one structural analysis (for Re (1010)) has been reported in the literature [1]. As a peculiarity, this kind of surface may exhibit two types of termination as illustrated in fig. 1. The coordination of the topmost atoms differs for the two terminations. In termination A each atom of the top layer is surrounded by four nearest neighbours in the second layer with a relatively small layer spacing. Modifaction B shows a surface atom surrounded by only two nearest neighbours in the second layer with much larger spacing between the two topmost layers. Termination B obviously exhibits a much stronger surface corrugation, and pronounced relaxation effects in the topmost layers are most likely. The differing corrugations of the two surface terminations provide quite different adsorption sites.In contrast to other transition metals relatively few investigations have dealt with cobalt single crystal surfaces. Concerning the hexagonal Co phase LEED investigations were reported only for the (0001) [2][3][4] and for the (1120) surface [5]. In this work we present a LEED structure analysis of the clean Co(1010) surface. The analysis was carried out applying the automatic optimization scheme and the rDE-factor developed by Kleinle et al. [6], final results were cross-checked with standard r-factor methods.The experiments were carded out in a standard UHV chamber at a base pressure p < 10-8pa. Details about the experimental setup are described elsewhere [7]. The cobalt single crystal with a size of 6 mm diameter and 1 mm thickness was orientated within 0.5 ° in the [1010] direction by Lamprecht GmbH, D-7531 Neuhausen. After mechanical polishing the crystal was electrochemically etched as described by Welz et al. [5] resulting in a mirror-like finish. Thereafter the crystal was demagnetized by a Helmholtz coil, spotwelded between two tantalum wires and attached to a sample manipulator. The crystal was adjusted on the sample manipulator in a way to allow normal incidence within 0.5 o. The crystal temper-0039-6028/91/$03.50 © 1991 -Elsevier Science Publishers B.V. (North-Holland)
The structure of the clean Co(1010) surface has been analysed by LEED. Application of a recently developed computational scheme reveals the prevalence of the termination A in which the two topmost layers exhibit a narrow spacing of 0.62 A, corresponding to a 12.8( + 0.5)% contraction with respect to the bulk value, while the spacing between the second and third layer is slightly expanded by 0.8( + 0.2)%.The (1010) surface of a hcp crystal represents the counterpart to the well-known (110) plane of fcc crystals. In contrast to the latter, however, so far only one structural analysis (for Re (1010)) has been reported in the literature [1]. As a peculiarity, this kind of surface may exhibit two types of termination as illustrated in fig. 1. The coordination of the topmost atoms differs for the two terminations. In termination A each atom of the top layer is surrounded by four nearest neighbours in the second layer with a relatively small layer spacing. Modifaction B shows a surface atom surrounded by only two nearest neighbours in the second layer with much larger spacing between the two topmost layers. Termination B obviously exhibits a much stronger surface corrugation, and pronounced relaxation effects in the topmost layers are most likely. The differing corrugations of the two surface terminations provide quite different adsorption sites.In contrast to other transition metals relatively few investigations have dealt with cobalt single crystal surfaces. Concerning the hexagonal Co phase LEED investigations were reported only for the (0001) [2][3][4] and for the (1120) surface [5]. In this work we present a LEED structure analysis of the clean Co(1010) surface. The analysis was carried out applying the automatic optimization scheme and the rDE-factor developed by Kleinle et al. [6], final results were cross-checked with standard r-factor methods.The experiments were carded out in a standard UHV chamber at a base pressure p < 10-8pa. Details about the experimental setup are described elsewhere [7]. The cobalt single crystal with a size of 6 mm diameter and 1 mm thickness was orientated within 0.5 ° in the [1010] direction by Lamprecht GmbH, D-7531 Neuhausen. After mechanical polishing the crystal was electrochemically etched as described by Welz et al. [5] resulting in a mirror-like finish. Thereafter the crystal was demagnetized by a Helmholtz coil, spotwelded between two tantalum wires and attached to a sample manipulator. The crystal was adjusted on the sample manipulator in a way to allow normal incidence within 0.5 o. The crystal temper-0039-6028/91/$03.50 © 1991 -Elsevier Science Publishers B.V. (North-Holland)
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