Dimensional crossover and chirality of boron adsorbates on copper (110) surfaces

A copper boride phase found on Cu(110) exhibits dimensional crossover from 1D to 2D structures. The discovered surface phase, 7×`1'-B/Cu(110), is composed of alternating two-atom and three-atom rows that are separated by trenches. The narrower rows behave as a 1D template for atomic boron chains, and the wider rows provide a new dimensional degree of freedom that facilitates the generation of 2D clusters with chirality. The 7×`1' phase is nonperiodic in the chain direction and exhibits intermediate boron coverage, between that of the quasiperiodic 1D and periodic 2D phases of copper boride on Cu(110), demonstrating a unique feature of phase transitions at the surface.