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UCL - Prof. Rowe - Giant piezoresistance at interfaces and surfaces

Le Vendredi 10 Avril 2009 de 10h45 à 10h45
Seminar announcement - Friday April 10th at 10h45, auditorium BARB 21.

Prof. Alistair ROWE
from Laboratoire de Physique de la Matière Condensée, Ecole Polytechnique, Palaiseau, France.

Title: Giant piezoresistance at interfaces and surfaces

Abstract - The piezoresistance of silicon has been known for more than 50 years and results from a change in the bulk band structure due to an applied mechanical stress. In particular, the mobility of the charge carriers is modified due to a change in the effective mass. Here we present two novel giant piezoresistance effects in silicon based structures. In the first, the bulk silicon piezoresistance is used to switch current between the metallic and semiconducting parts of a metal/semiconductor hybrid structure. Since the metal is several orders of magnitude more conductive than the semiconductor, this results in a piezoresistance of the hybrid structure almost 10 times larger than that of homogenous bulk silicon. In the second, a giant piezoresistance effect recently observed in suspended silicon nanowires is shown to be related to the degree of surface depletion. Unlike the bulk silicon piezoresistance, the origin of this phenomenon is a change in the charge carrier density and not the mobility. This previously unobserved phenomenon is analogous to the gate induced pinching-off of the conduction channel in a field effect transistor, and so may be called the “piezopinch” effect. Exponential changes in resistance with stress are possible and piezoresistances up to 40 times larger than bulk silicon have been reported. The implications of these effects for the electrical detection of ultra-small movements in micro- and nano- electromechanical systems (MEMS/NEMS) will also be discussed.

Jean-Pierre Raskin (jean-pierre.raskin@uclouvain.be)

Dernière mise à jour par EDT MAIN Samedi 28 Mars 2009