Vicinal surfaces with arrays of atomic steps have important applications in catalysis, nanostructure growth, or electronic band engineering, since steps are active sites for chemical reactions, as well as nucleation and electron scattering centers. Given the infinite possibilities for the orientation of a vicinal surface, it is important to perform systematic investigations, in order to identify optimal substrates for specific functions. Using macroscopically curved crystal samples one can systematically probe entire families of vicinal planes with standard surface science techniques. This is done here for vicinal Ag(111) surfaces featuring the so-called fully- or 100%-kinked steps. Fully-kinked monatomic steps (height h=2.35 Å) run parallel to the [112̅] direction and have six-fold atomic coordination, as compared with the seven-fold coordinated close-packed steps, which are oriented along the [11̅0] direction. In such fully-kinked Ag(111) vicinals we investigate electronic and structural properties with STM, LEED and Angle-Resolved Photoemission (ARPES), and test both the growth of BiAg2 alloys and the on-surface synthesis of zig-zag polymers. The sample is a Ag single crystal curved around the (645) direction, such that the vicinal angle α can be tuned from the Ag(111) plane, beyond the Ag(423) surface, up to α=18º. As done in previous works on close-packed Ag(111), Cu(111) and Au(111) vicinals, we study the probability distribution of the terrace size d as a function of the vicinal angle from STM images, and probe the scattering of the Shockley state at the fully-kinked step by ARPES. We find that fully-kinked vicinals exhibit exceptional ordering, allowing one to visualize the universal, structural transformation of vicinal metal surfaces with unprecedented precision. This opens the way to a fine test of statistical models of step-lattices largely debated in the past. As shown in the Figure, the Shockley state analysis reveals a much stronger scattering strength at the fully-kinked step when compared to the closed-packed, leading to a dramatic decrease of the surface electron density in vicinal surfaces, that is, to a complete electron depletion of Ag(111) terraces with d <1.6 nm. Next we tested the growth of the BiAg2 monolayer, and observed the presence of magic vicinal angles at which one can achieve atomically sharp BiAg2 step grids, ideal to explore spin scattering properties. Finally we explored the on-surface synthesis of DMTP zig-zag polymers, where we also found optimal crystal orientations to template well-oriented onedimensional chains, such as to facilitate spectroscopic characterization by ARPES.

Resumen del trabajo presentado al Symposium on Surface Science (3S), celebrado en St. Christoph am Arlberg (Austria) del 25 de febrero al 10 de marzo de 2018.

We acknowledge financial support from the Spanish Ministry of Economy (grant MAT2017-88374-P) and the Basque Government (grant IT621-13).

Peer reviewed