Chemiresistive response of silicon nanowires to trace vapor of nitro explosives

Silicon nanowires are observed to behave as chemically modulated resistors and exhibit sensitive and fast electrical responses to vapors of common nitro explosives and their degradation by-products. The nanowires were prepared with a top-down nano-fabrication process on a silicon-on-insulator wafer. The surface of the silicon nanowires was modified by plasma treatments. Both hydrogen and oxygen plasma treatments can significantly improve the responses, and oxygen plasma changes the majority carrier from p- to n-type on the surface of silicon nanowire thin films. The sensitivity is found to increase when the cross-section of the nanowires decreases. An improved sensing response to nitro explosive vapors was observed on silicon nanowires after their surface was modified by plasma.