2008 NSTI Nanotechnology Conference and Trade Show - Nanotech 2008 - 11th Annual

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Increased Piezoresistive Effect in Crystalline and Polycrystalline Si Nanowires

K. Reck, J. Richter, O. Hansen, E.V. Thomsen
Technical University of Denmark, DK

piezoresistivity, silicon nanowires, top-down, P-type, doping dependence

This paper presents measurements of the size and doping dependence of the piezoresistive effect in top-down fabricated p-type crystalline and polycrystalline silicon nanowires. Test chips with 6 differently sized piezoresistors and integrated contacts for electrical four point measurements have been fabricated by e-beam lithography. A uniaxial stress is applied to the test chips using a 4-point bending fixture. The results show that an increase in the piezoresistive effect of up to 6.2 times that of bulk silicon is present in moderately doped silicon nanowires. At high doping levels, no or little increase in the piezoresistive effect is observed with decreasing dimensions. Below 100 nm width, boundary scattering is dominant in highly doped nanowires, resulting in a non-measurable change in resistance with applied stress. In polysilicon an increase in the piezoresistive effect of up to 1.39 times that of bulk is observed. The increase in the piezoresistive effect in both crystalline and polycrystalline silicon is of great importance in the field of highly sensitive devices, e.g. in the field of biomedical sensing. Parallel fabrication using nanoimprint for future industrial scale massfabrication and the influence of passivation on the piezoresistive effect is currently being investigated.

Nanotech 2008 Conference Program Abstract