7 NWs and the islands find more grown on the Si(110) surface. It can be seen that the NWs and 3D islands have sharply different contrast. The 3D islands are much brighter than the NWs, while the NWs are just a little brighter than the Si(110) substrate. This result indicates that the average atomic weight of the 3D islands is much greater than that of the NWs, while the average atomic weight of the NWs is slightly larger than that of the Si substrate. Therefore, the 3D islands
and NWs have different chemical compositions. The 3D islands correspond to the Mn-rich silicide such as Mn5Si3, and the NWs correspond to the Si-rich phase MnSi~1.7. This conclusion is consistent with that reported for the Mn silicides formed on the Si(111) VX-809 chemical structure surface [20, 21]. Figure 6 Atomically resolved STM image of the manganese silicide NW and its tunneling current-voltage properties. (a) Atomically resolved STM image (10 × 10 nm2) of an ultrafine manganese silicide NW grown on the Si(110) surface and (b) the scanning tunneling spectra measured on top of the NW showing semiconducting characteristics with a bandgap of approximately 0.8 eV. The red and blue curves were obtained on two different positions on the NW. Figure 7 Ex situ BE-SEM image of the manganese silicide NWs and 3D islands grown on Si(110) surface. Conclusions In summary, the influence of growth
conditions such as growth temperature, deposition rate, and deposition time on the formation of MnSi~1.7 NWs on a Si(110) surface has been investigated by STM. High growth temperature and low Mn deposition rate are found to be favorable for the formation of NWs with a large aspect ratio, indicating
that the supply of free Si atoms per unit time plays a crucial role in the growth of the NWs. The NWs orient solely with the long axis along the Si direction. The I-V curves measured on top of the NWs, and the BE-SEM image reveal that the NWs consist of MnSi~1.7. The growth of the parallel MnSi~1.7 NWs on the Si substrate provides an opportunity for the study of electronic properties of NWs and the fabrication of nanoelectronic devices with novel functions. Acknowledgements This work was supported by the National Natural Science Foundation of China under grant no. 61176017 and the Innovation Program PFKL of Shanghai Municipal Education Commission under grant no. 12ZZ025. References 1. Liang S, Islam R, Smith DJ, Bennett PA, O’Brien JR, Taylor B: Magnetic iron silicide nanowires on Si(110). Appl Phys Lett 2006, 88:113111.CrossRef 2. He Z, Smith DJ, Bennett PA: Epitaxial DySi2 BIBF 1120 nanowire formation on stepped Si(111). Appl Phys Lett 2005, 86:143110.CrossRef 3. He Z, Smith DJ, Bennett PA: Endotaxial silicide nanowires. Phys Rev Lett 2004, 93:256102.CrossRef 4. Preinesberger C, Becker SK, Vandré S, Kalka T, Dähne M: Structure of DySi2 nanowires on Si(001). J Appl Phys 2002, 91:1695.CrossRef 5.
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