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Effets de piézorésistance géante dans les micro- et nanofils de  silicium

The NAM6 group has been working actively in the field of piezoresistance in silicon micro and nano structures since 2006. Its scientific output – in collaboration with Ecole Polytechnique (Paris) and the University of Geneva – has earned the group an international reputation as one of the world leaders in the subject.

Figure 1: (a) A 4 terminal aluminium-silicon hybrid structure fabricated at IEMN which displays giant piezoresistance. Scale bar = 20 µm. (b) A top-down silicon nanowire fabricated at IEMN used for giant piezoresistance studies. Scale bar = 2 µm.

Figure 1: (a) A 4 terminal aluminium-silicon hybrid structure fabricated at IEMN which displays giant piezoresistance. Scale bar = 20 µm. (b) A top-down silicon nanowire fabricated at IEMN used for giant piezoresistance studies. Scale bar = 2 µm.

The group has published three articles on piezoresistivity in silicon in the journal Physical Review Letters – co-authored with Ecole Polytechnique and Geneva. The first letter [Phys. Rev. Lett. 100 145501 (2008)] reported giant piezoresistance (GPZR) in an aluminium-silicon hybrid structure (Fig. 1a). The second letter [Phys. Rev. Lett. 105, 226802 (2010)] reported experimental data concerning the presence of GPZR in silicon micro and nanowires (Fig. 1b). The third letter [Phys. Rev. Lett. 108, 256801 (2012)] charted piezoresistance in silicon at applied stresses – in the GPa range, under compression – previously unattained (Fig. 2). This latter result has implications in strained silicon transistor technology. Recent reports of giant GPZR in silicon nanowires (He and Yang, Nature Nanotech. 2006) – if true – enable one to imagine a highly sensitive novel range of nano-electromechanical sensors.

 

Figure 2: Piezoresistance in bulk p-type (110) silicon in compression up to 3 GPa.

Figure 2: Piezoresistance in bulk p-type (110) silicon in compression up to 3 GPa.

 

Bulk silicon, depending on the doping and crystal direction, has a piezoresistance coefficient of ~100×10-11 Pa-1. Using silicon nanowires a factor as high as ~3500×10-11 Pa-1 has been observed, >30 times larger than the bulk value reported by Smith in 1954. Our research has been focused on identifying the physical mechanism behind GPZR. An understanding – not given by He and Yang in their 2006 paper – would enable us to optimise the effect and effectively apply it to new sensor technologies. The results of our collaborative research have been reported widely in the international press (reputable scientific magazine articles and scientific news web sites). Since 2008, the research has been financed by the French Agence Nationale de la Recherche.