Comprehensive Analytical Modelling of an Absolute pH Sensor
Cristina Medina-Bailon,
Naveen Kumar,
Rakshita Pritam Singh Dhar,
Ilina Todorova,
Damien Lenoble,
Vihar P. Georgiev,
César Pascual García
Affiliations
Cristina Medina-Bailon
Device Modelling Group, School of Engineering, University of Glasgow, Glasgow G12 8LT, UK
Naveen Kumar
Device Modelling Group, School of Engineering, University of Glasgow, Glasgow G12 8LT, UK
Rakshita Pritam Singh Dhar
Device Modelling Group, School of Engineering, University of Glasgow, Glasgow G12 8LT, UK
Ilina Todorova
Device Modelling Group, School of Engineering, University of Glasgow, Glasgow G12 8LT, UK
Damien Lenoble
Nano-Enabled Medicine and Cosmetics Group, Materials Research and Technology Department, Luxembourg Institute of Science and Technology (LIST), L-4362 Esch-sur-Alzette, Luxembourg
Vihar P. Georgiev
Device Modelling Group, School of Engineering, University of Glasgow, Glasgow G12 8LT, UK
César Pascual García
Nano-Enabled Medicine and Cosmetics Group, Materials Research and Technology Department, Luxembourg Institute of Science and Technology (LIST), L-4362 Esch-sur-Alzette, Luxembourg
In this work, we present a comprehensive analytical model and results for an absolute pH sensor. Our work aims to address critical scientific issues such as: (1) the impact of the oxide degradation (sensing interface deterioration) on the sensor’s performance and (2) how to achieve a measurement of the absolute ion activity. The methods described here are based on analytical equations which we have derived and implemented in MATLAB code to execute the numerical experiments. The main results of our work show that the depletion width of the sensors is strongly influenced by the pH and the variations of the same depletion width as a function of the pH is significantly smaller for hafnium dioxide in comparison to silicon dioxide. We propose a method to determine the absolute pH using a dual capacitance system, which can be mapped to unequivocally determine the acidity. We compare the impact of degradation in two materials: SiO2 and HfO2, and we illustrate the acidity determination with the functioning of a dual device with SiO2.
