Thin films Titanium dioxide pH sensors Extended gate field effect transistor (EGFET) Field effect transistors Sensing membranes pH effects Oxide films Sol-gels Thermoelectric equipment Tin oxides Titanium oxides Annealing Electronic equipment Indium tin oxide substrates Sol-gel spin coating method Thin film circuits Zinc oxide pH Annealing condition Annealing process Annealing time Bilayer composites Buffer solutions Coated glass substrates Composite films Constant temperature Deposition Deposition temperatures Different substrates