STM andab initiostudy of holmium nanowires on a Ge(111) surface

Abstract

A nanorod structure has been observed on the $\mathrm{Ho}∕\mathrm{Ge}\left(111\right)$ surface using scanning tunneling microscopy (STM). The rods do not require patterning of the surface or defects such as step edges in order to grow as is the case for nanorods on Si(111). At low holmium coverage the nanorods exist as isolated nanostructures while at high coverage they form a periodic $5\times 1$ structure. We propose a structural model for the $5\times 1$ unit cell and show using an ab initio calculation that the STM profile of our model structure compares favorably to that obtained experimentally for both filled and empty states sampling. The calculated local density of states shows that the nanorod is metallic in character.