A VIBRATIONAL STUDY OF THE HYDROGEN INDUCED RECONSTRUCTIONS ON CU(110)

Hydrogen adsorbed at 100 K on Cu(110) induces a (1 × 3) surface reconstruction observable in LEED in the coverage region 0.2 > φH > 0.8. Two loss peaks associated with the hydrogen adsorbed in this phase are observed in HREELS at 620 and 505 cm-1. These features persist throughout the coverage range 0.0 < φH < 1.0. Additional losses associated with hydrogen on a (1 × 2) reconstructed surface appear at φH > 0.8 where a conversion of the (1 × 3) to the (1 × 2) phase is evident in LEED. Hydrogen adsorption at 300 K leads directly to the (1 × 2) reconstructed phase observable in LEED over the coverage range 0.1 < φH < 1.0 and exhibits associated HREELS losses at 765, 950 and 1150 cm-1. Heating the (1 × 3) phase formed at 100 K irreversibly produces the (1 × 2) reconstruction in the temperature range 140-190 K. We assign the modes observed in the (1 × 3) phase to hydrogen in a pseudo four-fold hollow site on a buckled reconstructed surface. The modes on the (1 × 2) phase are associated with hydrogen in a tilted trigonal site on a missing row reconstructed surface. The hydrogen site transition from (1 × 3) to (1 × 2) on Cu(110) is analogous to the behaviour in metal hydrides where a conversion from octahedral to tetrahedral hydrogen coordination occurs for increasing hydrogen concentrations. © 1990.