Direct measurement of shear piezoresistance coefficient on single crystal silicon nanowire by asymmetrical four-point bending test

Abstract

This research evaluated the shear piezoresistance property of p-type single crystal silicon nanowire (SiNW) by the asymmetrical four-point bending (AFPB) technique proposed by the authors [1]. We fabricated the p-type SiNW on the AFPB test specimen with “V”-shaped notches (V-notches) made of single crystal silicon. Bending the specimen by the asymmetrical four point-supports, simple shear stress can be produced at the center of the specimen. Consequently, we have succeeded in evaluating the shear piezoresistance coefficient of SiNW directly, which was found to be π <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">44</sub> =203 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-11</sup> Pa <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> at an impurity concentration of 7.3 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">18</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> . This value is 2.1 times larger than that of p-type piezoresistors used in conventional piezoresistance sensors on a micrometer scale. The proposed evaluation technique and obtained result will be effective for design application of high-sensitivity mechanical sensors integrating SiNW piezoresistance elements.