Discriminative power of chemically sensitive silicon nanowire field effect transistors to volatile organic compounds.

We report on the sensing of different polar and nonpolar volatile organic compounds (VOCs) in an atmosphere with background humidity (relative humidity: 40%), using molecularly modified silicon nanowire field effect transistors (SiNW FETs). In this endeavor, a systematic comparative analysis is performed with: (i) SiNW FETs that were functionalized with a series of molecules having different electron-withdrawing and electron-donating end groups; and (ii) SiNW FETs that are functionalized with a series of molecules having similar functional groups but different backbone lengths. The analysis of the sensing signals are focused on three main FET parameters: (i) changes in the threshold voltage, (ii) changes in the carrier mobility, and (iii) changes in the on-current, compared to the baseline values under vacuum. Using discriminant factor analysis, the performance of the molecularly modified SiNW FETs is further analyzed as sensors array. The combination of sensors having the best discriminative power between the various VOCs are identified and discussed in terms of their constituent surface modifications.