Eur. Phys. J. D 45, 433-437 (2007)
https://doi.org/10.1140/epjd/e2007-00213-7

The structure of cobalt nanoparticles on Ge(001)

University of Rostock, Department of Physics, Universitätsplatz 3, 18051 Rostock, Germany

Corresponding author: ^a kristian.sell@uni-rostock.de

Received: 20 February 2007
Revised: 3 May 2007
Published online: 27 June 2007

Abstract

In this contribution we present scanning tunnelling microscopy (STM) and spectroscopy (STS) investigations on isolated cobalt clusters in contact with Ge(001). Mass-filtered nanoparticles with diameters ranging from 3 to 11 nm are generated using an arc cluster ion source (ACIS) and deposited under soft landing conditions (E_kin/atom < 0.5 eV). Since the tip radius is of the same order as the nanoparticle diameters the recorded STM images are significantly affected by tip folding. By means of the “blind reconstruction method" it is possible to approximate the tip shape. After a respective deconvolution of the image structural features of the particle facets become observable. According to the equilibrium shape of the clusters being a truncated octahedron in the size range under investigation, hexagonal and rectangular features appear in the images. STS is sensitive to occupied and unoccupied states near the Fermi level and reveals the existence of distinct states in the tunnelling conductivity of the substrate as well as on the clusters. The richly structured density of states of the germanium surface serves here as tip condition test. First measurements of the tunnelling conductivity of the Co_N/Ge(001) are presented and discussed.