It is getting more important to elucidate electrical transport properties of individual nanostructures. We have shown the versatility of double-scanning-probe tunneling microscope through the measurements on nanowires (NWs) [1,2]. Here, we performed resistance measurements of diplatinum-silicide (Pt2Si) NWs (H: 0.2-1 nm, W: 5-10 nm, L: 100-1000 nm) which are epitaxially formed on Si(001) substrate [3]. The resistances between the two probes (Rs) were measured by changing the distance between the two (L). The result showed that R linearly decreased as L decreased. Resistivity of the NWs estimated from the slope of R-L curve was almost the same as that of the bulk Pt2Si. In the measurement of erbium-disilicide (ErSi2) NWs whose dimension was almost the same as that of Pt2Si NWs [4], the R-L curve also showed linear relationship. However, the estimated resistivity was approximately one order of magnitude greater than that of bulk ErSi2, which was attributed to surface scattering in the nano-conductor [2].
Next, we measured the resistances between two separate NWs. In the case of ErSi2 NW, the resistances were more than ten times larger than those measured on a single NW, while those between two separate Pt2Si NWs was less than only three times the resistances measured on a single NW, indicating that the leakage current through the Si substrate contributed to the R-L measurement on Pt2Si NWs. To quantitatively elucidate the contribution of the leakage current, spreading resistances from a contacted probe to the substrate were measured with changing the contact position on a NW. The measured resistances combined with the result of R-L measurement on identical NW can be quantitatively explained with a simple model of current path around the NW based on finite element method, resulting in the estimation of the resistivity of the NW itself.
1) M. Aono et al., Oyo Buturi 67, 1361 (1998). (in Japanese)
2) O. Kubo et al., Appl. Phys. Lett. 88, 254101 (2006)
3) D. K. Lim et al., Nanotechnology 18, 095706 (2007)
4) Y. Chen et al., Appl. Phys. Lett. 76, 4004 (2000)
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