A highly long-term stable silicon-based pH sensor fabricated by pulsed laser deposition technique

Abstract

A highly long-term stable pH sensor based on a capacitive electrolyte insulator semiconductor heterostructure has been developed. The pH-sensitive gate insulator material Al 2O 3 has been deposited by means of the pulsed laser deposition technique. The basic characteristics of the sensor device, such as pH sensitivity, stability, selectivity, sensor drift and response time have been investigated using capacitance/voltage measurements. Furthermore the physical structure and the stoichiometric composition of the deposited Al 2O 3 layers have been studied by Rutherford backscattering spectrometry, ion channeling and transmission electron microscopy. According to the results obtained during a measurement period of more than 600 days, the sensor possesses a high pH sensitivity of about 56 mV/pH including a small baseline drift of the sensor signal of less than 1 mV per day.