Scanning tunneling microscopy observation of phase-transition phenomena in the Cs/Cu(110) system: Evidence for a two-step disordering mechanism of a uniaxial (1×3) phase

The disordering of the uniaxial Cs/Cu(110) (1×{}3) phase was studied by scanning tunneling microscopy as a test case for the theoretical predictions of a two-step disordering mechanism. Lowering the Cs coverage first causes the formation of domain walls in the (1×{}3) phase, indicating a transition from a two-dimensional commensurate solid into an incommensurate floating solid. Dislocations in this wall pattern lead to progressing disordering into an incommensurate fluid. Further coverage reduction stabilizes fluctuating domains of a (1×{}4) phase, which signal a close by continuous solid to fluid transition.