Fluoride ion and hydrofluoric acid detection via silicon nanosheet field-effect transistor sensor

Abstract

Fluoride ion (F–) and hydrofluoric (HF) acid are widely used, but they are highly toxic to the health and the natural environment. Sensors based on the field-effect transistor (FET) are commonly considered for chemical applications due to their small size and simple fabrication method. However, there has not been reported on the FET-based sensor for detecting F– ion and HF acid in the literature. Here, we demonstrate F– and HF acid sensors based on the FET, enabling sensitive detection in a small form factor. In particular, our FET sensor incorporates silicon nanosheet (SN) as the channel structure and polycrystalline lanthanum fluoride as a sensing membrane. Therefore, the fabricated sensor presents high responsivity (SR[M]) of 455.7 %/log[F–] for F– and high SR[M] of 392.4 %/log[HF] and has extremely low limit of detection of 10.20 ppb for F– and 32.04 ppb for HF acid. Moreover, it shows a good selectivity over other ions such as CO32–, NO3–, PO43–, and SO42– and a low hysteresis current of 0.81 %. Finally, the performance of our HF sensor has been excellently demonstrated by the fabricated real-time HF sensor system and exhibits negligible error (less than 5 %) comparable to a commercial one.