Light-addressable potentiometric fluoride (F−) sensor

In this work, light-addressable potentiometric sensor (LAPS) has been investigated for fluoride (F−) sensing in aqueous medium. Vacuum-evaporated LaF3 has been studied as the fluoride-sensing layer in the LAPS heterostructure. Instead of using the conventional structure of Si/SiO2/LaF3 or Si/SiO2/Si3N4/LaF3, a simple structure of Si/LaF3 has been prepared as the LAP fluoride-sensor. The sensor was prepared with 50 nm LaF3 layer on 300 μm Si. The sensor hardly shows fluoride-sensitivity without annealing, but it shows quite linear response in the range of pF1–5 with a sensitivity of ≈49 mV/pF for LaF3 layer annealed at 400 °C for 10 min. From the experimental result it appears that Si/LaF3 structure can be used for the sensing and imaging the distribution of fluoride ion in aqueous medium.