Cobalt induced nanocrystals on Ge(001)

SURFACE SCIENCE

卷:606

Article

Mocking, T. F.¹  Hlawacek, G.¹  Zandvliet, H. J. W.¹ 

[1] Univ Twente, MESA Inst Nanotechnol, NL-7500 AE Enschede, Netherlands

关键词: Cobalt;    Nanocrystals;    Shape transition;    Germanium;    Surface stress;    STM;    Helium Ion Microscopy;   

DOI  :  10.1016/j.susc.2012.02.007

来源: Elsevier

【 摘 要 】

The deposition of several monolayers of cobalt on germanium (001) substrates results in the formation of two types of clusters: flat-topped and peaked nanocrystals. Scanning tunneling spectroscopy and helium ion microscopy measurements reveal that these nanoctystals contain cobalt The shape evolution of the flat-topped and peaked nanocrystals as a function of their size is investigated with scanning tunneling microscopy. For small sizes the nanocrystals are compact. Beyond a critical size, however, the peaked nanocrystals exhibit an elongated shape, whilst the flat-topped nanocrystals remain compact The shape transition of the peaked nanocrystals is driven by a competition between boundary and strain energies. For small sizes the boundary energy is the dominant term leading to a minimization of the peaked nanocrystal's perimeter, whereas at larger sizes the strain energy wins resulting in a maximization of the perimeter. On the top facet of the flat-topped nanocrystals one-dimensional structures are observed that are comprised of small square shaped units of about 1 nm(2). Time-resolved scanning tunneling microscopy measurements reveal that these square shaped units are dynamic at room temperature. (C) 2012 Elsevier B.V. All rights reserved.

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