Abstract We report the formation and local electronic structure of Ge clusters on the Si(111)-7$\times $7 surface studied by using variable temperature scanning tunnelling microscopy (VT-STM) and low-temperature scanning tunnelling spectroscopy (STS). Atom-resolved STM images reveal that the Ge atoms are prone to forming clusters with 1.0 nm in diameter for coverage up to 0.12 ML. Such Ge clusters preferentially nucleate at the centre of the faulted-half unit cells, leading to the `dark sites' of Si centre adatoms from the surrounding three unfaulted-half unit cells in filled-state images. Bias-dependent STM images show the charge transfer from the neighbouring Si adatoms to Ge clusters. Low-temperature STS of the Ge clusters reveals that there is a band gap on the Ge cluster and the large voltage threshold is about 0.9 V.
Received: 24 January 2007
Revised: 04 April 2007
Accepted manuscript online:
PACS:
73.22.-f
(Electronic structure of nanoscale materials and related systems)
(Surface states, band structure, electron density of states)
Fund: Project supported by the National
Natural Science Foundation of China (Grant Nos~90406022 and 10674159).
Cite this article:
Ma Hai-Feng(马海峰), Xu Ming-Chun(徐明春), Yang Bing(杨冰), Shi Dong-Xia(时东霞), Guo Hai-Ming(郭海明), Pang Shi-Jin(庞世瑾), and Gao Hong-Jun(高鸿钧) Formation and local electronic structure of Ge clusters on Si(111)-7×7 surfaces 2007 Chinese Physics 16 2661
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