Scanning tunnelling microscopy is utilized to investigate the local bias voltage tunnelling dependent transformation between (2×1) and c(4×2) structures on Ge(001) surfaces, which is reversibly observed at room temperature and a critical bias voltage of -0.80 V. Similar transformation is also found on an epitaxial Ge islands but at a slightly different critical bias voltage of -1.00 V. It is found that the interaction between the topmost atoms on the STM tip and the atoms of the dimers, and the pinning effect induced by Sb atoms, the vacancies or the epitaxial clusters, can drive the structural transformation at the critical bias voltage.
Different In/Ge(001) nanostructures have been obtained by annealing the samples at 320 C with different coverages of In.Annealing a sample with a critical coverage of 2.1 monolayer of In,different In/Ge(001) nanostructures can be obtained at different temperatures.It is found that thermal annealing treatments first make In atoms form elongated Ge { 103 }-faceted In-clusters,which will grow wider and longer with increasing temperature,and finally cover the surface completely.
