ZETA POTENTIAL MEASUREMENTS OF TA2O5 AND SIO2 THIN-FILMS

Flat-plate streaming potential measurements were carried out on samples of tantalum pentoxide and silicon dioxide. The Ta2O5 samples were 150 nm films on silicon substrates, fabricated by the deposition of tantalum followed by oxidation in pure oxygen at 550°C. The SiO2 samples were 1 μm thick films prepared by steam oxidation of a silicon substrate. The electrolyte used in the measurements was NaCl, at concentrations of 10-1, 10-2, and 10-3 M. The point of zero zeta potential (pHiep) was between 2.7 and 3.0 for the Ta2O5 samples and between 2.6 and 3.2 for SiO2. In both cases, this agrees well with previous literature determinations, and indicates the reliability of the flat-plate method. We observed that the zeta potential of thin films of Ta2O5 was more stable and had less hysteresis than the zeta potential of thin SiO2 films. © 1991.