Ir{100}-(1 x 3)-H, an intermediate phase between the (1 x 1) and the (1 x 5) phases of Ir{100}

Clean Ir{1 0 0} surfaces reconstruct to forma (1 x 5) overlayer. When hydro gen adsorbs on Ir{1 0 0}, a metastable (1 x 3) phase is formed. Temperature programmed desorption results show that hydrogen is needed to stabilise th is phase. When hydrogen is desorbed the structure reverts back immediately to the (1 x 5) phase. The (1 x 3) structure has been determined using quant itative low energy electron diffraction. The best-fit structure has three i ridium and five hydrogen atoms per unit cell. Two of the hydrogens lie in t he subsurface region and stabilise the (1 x 3) phase. (C) 2001 Elsevier Sci ence B.V. All rights reserved.