Study on pH(pzc) and surface potential of tin oxide gate ISFET

In this study, capacitance-voltage (C-V) and current-voltage (I-V) measurem ents were used to investigate pH(pzc) (point zero of charge) and surface po tential of a tin oxide gate ISFET. Dual FETs configuration: AlSnO2/Si3N4/Si O2 gate MOSFET and SnO2/Si3N4/SiO2 gate ISFET were fabricated for this stud y. Experimental results show that different operations of ISFETs will yield different values of the pH(pzc) and surface potential. For example, the pH (pzc) is 5.6 for the ISFET's operation at the flat band condition and the p H(pzc) is 6 for the ISFET's operation at the linear region. This phenomenon can be explained by the influence of charge density at the semiconductor-i nsulator interface. Additionally, according to a series of theoretical simu lations, we can conclude that the surface parameter Delta pK is the dominat ed factor of pH response in ISFET. Experimental results and theoretical sim ulations can achieve a good curve fitting when appropriate surface paramete rs for tin oxide are chosen. (C) 1999 Elsevier Science S.A. All rights rese rved.