EIS capacitor sensor, with TiO2 dielectric, applied in the evaluation of phosphate in wastewater

This work presents the development of an Electrolyte-Insulator-Semiconductor (EIS) device with a built-in reference electrode to detect phosphate in wastewater. The idea of developing this device comes from the need to improve the use of water processed by the effluent treatment plant. After treatment process, a fraction of the water can be used as wastewater, this water cannot be consumed, however it can be used for other purposes including cleaning public spaces, such as streets and squares. In the fabrication process of the EIS device, titanium oxide (TiO2) deposited on a silicon substrate was used as a sensor element, and titanium nitride (TiN) was used for the reference electrode. Both materials were deposited by the reactive sputtering process. Aluminum (Al) was used for the electrode on the back of the slide deposited by evaporation. Preliminary results of structural and electrical characterizations indicate that the manufactured device has good sensitivity to phosphate ions (66 mV/ppm). This sensitivity is due to the good quality of the film, which is shown using Raman spectroscopy, atomic force microscopy (AFM) and X-ray diffraction (XRD) techniques, in addition to electrical measurements.