A spectroscopy and microscopy study of Parylene-C OFETs for explosive sensing

Abstract

In this paper, we have explored Parylene-C (PC) as a sensing material for its unique signatures and selectivity for explosive sensing. We have used a bilayer deposition process to fabricate bottom-gate-topcontact (BGTC) OFET structures. Opening of dangling bonds on subjecting PC to plasma oxidation (POPC) renders these molecules to be employed as a receptor material in sensing vapors of both explosives and nonexplosives such as Trinitrotoulene (TNT), 1,3,5 trinitro- 1,3,5-triazacyclohexane(RDX), PETN, Dinitrobenzene (DNB), Nitrobenzene (NB), Benzoquinone (BQ) and Benzophenone (BP). The change in (a) the vibration modes of the molecule by infrared spectroscopy (FTIR) (b) surface potential of POPC by Kelvin Probe Force Microscopy (KPFM) and (c) electrical characterization by IV measurements of PC based OFET on exposing to vapors have been systematically studied. Different signatures for all the analytes have been observed while exact and perfect selectivity for TNT, RDX were found from I-V studies and for PETN by KPFM studies. Thus, the OFET device based chemical sensors demonstrated here with improved sensitivity and excellent selectivity, stand as promising candidates for explosives detection.