Adhesion properties of decagonal quasicrystals in ultrahigh vacuum

The atomic scale adhesion properties of two high-symmetry surfaces of decagonal Al-Ni-Co quasicrystals have been investigated using atomic force microscopy (AFM) in ultrahigh vacuum. Imaging the surface allowed us to distinguish the plastic regime from the elastic (reversible) regime of tip-sample contact. The work of adhesion of the atomically clean quasicrystal surface in the plastic regime is smaller than that of single crystalline Pt(111) by a factor of 10, reflecting a lower surface energy for the quasicrystal surface. However, the adhesion force must be reduced even further, in order to make measurements outside of the plastic regime possible. We present a strategy for doing this that involves chemical modi. cation of the surface or the tip, together with appropriate choice of mechanical contact parameters.