Evaluation of the piezoresistive effect in single crystalline silicon nanowires

This paper reports the design, fabrication and evaluation of piezoresistive effect of silicon nanowires (SiNWs). The SiNWs with the length of 2¿m, thickness of 40nm and width ranges from 35nm to 480nm have been fabricated by electron beam (EB) direct writing and reactive ion etching (RIE). The SiNWs are protected by a thermally grown SiO₂ to avoid the environment affect and to deactivate the outer layer, which was attacked during RIE. Dependence of piezoresistive effects on the width of the SiNWs has been evaluated. The results showed that when the width of the SiNWs reduces to nanometer size, the smaller the width, the bigger the piezoresistive coefficient. Longitudinal piezoresistive coefficient ¿_l[110] along ¿110¿ crystallographic orientation increased up to 60% when the width of SiNWs down from 480nm to 35nm.