Open Access Nano Express

Nickel-containing nano-sized islands grown on Ge(111)-c(2 × 8) and Ag/Ge(111)-(√3 × √3) surfaces

Tsu-Yi Fu1*, Agnieszka Tomaszewska12, Xiao-Lan Huang1, Jhen-Hao Li1, Po-I Hsieh1 and Ming-Kuan Jhou1

Author Affiliations

1 Department of Physics, National Taiwan Normal University, 88, Sec. 4 Ting-Chou Rd., Taipei 116, Taiwan

2 Institute of Physics, Jan Długosz University, Armii Krajowej Ave. 13/15, Częstochowa 42-200, Poland

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Nanoscale Research Letters 2013, 8:416  doi:10.1186/1556-276X-8-416

Published: 8 October 2013

Abstract

The formation of nano-islands on both a Ge(111)-c(2 × 8) surface and an Ag/Ge(111)-(√3 × √3) surface evaporated with 0.1 ML Ni was investigated by scanning tunneling microscopy (STM). We have noticed that at temperatures lower than 670 K, the reaction between Ni and the individual substrate surfaces proceeds to form different structures: flat-topped islands with a 2√7 × 2√7 or a 3 × 3 reconstruction on the Ni/Ge(111)-c(2 × 8) surface vs. islands with a 7 × 7 reconstruction on the Ni/Ag/Ge(111)-(√3 × √3) surface. From this we have inferred that within a temperature range between room temperature and 670 K, the intermediate Ag layer retards mixing between Ni and Ge atoms. As a result, the grown islands are composed of pure Ni atoms. Within a temperature range from 670 to 770 K, most islands produced on the Ag/Ge(111)-(√3 × √3) surface are identical with those formed on the Ni/Ge(111)-c(2 × 8) surface, suggesting that above 670 K, Ni atoms are likely to bind with Ge atoms. However, an essential difference between STM images of the surfaces under study exists in the appearance of large elongated islands on the Ni/Ag/Ge(111)-(√3 × √3) surface. The formation of the latter is explained in terms of a difference in energy for Ni diffusion on the Ge(111)-c(2 × 8) and Ag/Ge(111)-(√3 × √3) surfaces.

Keywords:
Ni; Ag; Ge(111); STM