A low energy pathway to CuCl2 at Cu(110) surfaces.

The reaction of hydrogen chloride gas with partially oxidised Cu(110) surfaces follows a different structural pathway than its reaction with a clean surface. In the latter case a c(2 x 2)Cl structure develops which is compressed in the [110] direction for chlorine atom concentrations greater than 5.5 x 10(14) cm(-2). In contrast, the presence of oxygen leads to the formation of linear "Cl-chains" orientated in the [100] direction which closely resemble those of bulk CuCl(2). These Cu(II) like structures are unstable at room temperature decomposing to form c(2 x 2)Cl. Using XPS and STM we have investigated the formation of the CuCl(2) like surface species and propose that it derives from the unusual reactivity of transient copper adatoms released from the p(2 x 1)O by the exothermic formation of water.