Electron Confinement in Surface States on a Stepped Gold Surface Revealed by Angle-Resolved Photoemission

STM images show that vicinal Au(788) surfaces are made up of a uniform array of (111)-oriented terraces of similar width $\left(\sim 3.8\mathrm{nm}\right)$. This uniformity makes it possible to study the electronic structure of the resulting step superlattice by angle-resolved photoemission. We show that for this terrace array the surface state appears to be broken up into one-dimensional quantum-well levels, indicating total electron confinement within the terraces. The angular resolution allows the probability density of the terrace quantum well state to be mapped in reciprocal space, complementing nicely the wave function measured in real space by STM.