Piezoresistance measurement on single crystal silicon nanowires

A p-type single crystal silicon nanowire bridge and a four-terminal nanowire element were fabricated by electron-beam direct writing. The piezoresistance was investigated in order to demonstrate the usefulness of these sensing elements as mechanical sensors. The longitudinal piezoresistance coefficient pi(l[110]) was found to be 38.7x10(-11) Pa-1 at a surface impurity concentration of Ns=9x10(19) cm(-3) for the nanowire bridge. The shear piezoresistance coefficient pi(44) was found to be 77.4x10(-11) Pa-1 at Ns=9x10(19) cm(-3) for the four-terminal nanowire element. These values are 54.8% larger than the values obtained from p(+) diffused piezoresistors, which are used in conventional mechanical sensors. (C) 2003 American Institute of Physics.