A HIGHLY LONG-TERM STABLE SILICON-BASED PH SENSOR FABRICATED BY PULSED-LASER DEPOSITION TECHNIQUE

A highly long-term stable pH sensor based on a capacitive electrolyte insulator semiconductor heterostructure has been developed. The pH-sen sitive gate insulator material Al2O3 has been deposited by means of th e 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/volta ge measurements. Furthermore the physical structure and the stoichiome tric composition of the deposited Al2O3 layers have been studied by Ru therford backscattering spectrometry, ion channeling and transmission electron microscopy. According to the results obtained during a measur ement period of more than 600 days, the sensor possesses a high pH sen sitivity of about 56 mV/pH including a small baseline drift of the sen sor signal of less than 1 mV per day.