Parameter dependent fabrication of Chromium nano-structures on Au(111) surface

摘要

Circular and rectangular Cr islands of nanometre size and monoatomic height exhibit an impromptu long range order on locally stepped Au(111) surface with narrow terraces. The circular islands are detached from the {100} microfaceted Au(111) step edges and nucleate between a pair of discommensuration lines of the herringbone reconstruction on  ≈ 9.5 nm wide terraces. In contrast, the rectangular islands are attached to the {111} microfaceted step edges and are formed on even narrower terraces of  ≈ 6 nm width. Both types of islands prefer the hcp region of the substrate as the nucleation centre. Cr deposition at elevated temperatures such as 470 K results in formation of triangular islands and spiral dislocations on wide substrate terraces. Interestingly however, at higher coverages of 3–4 ML, huge elongated ridges that are 90–260 nm in length, 10–20 nm in width and up to almost 3 nm height are observed. These ridges occur primarily along11¯0direction, with the rest forming at an angle of 60 or 120° with respect to this direction.