The Suitability of Ta2O5 as a Solid State Ion-Sensitive Membrane

Ta2O5 films were used as ion-sensitive membranes of a solid state H+ ion sensor. The responses of the Ta2O5 films to H+ ions were characterized by utilizing 2 kinds of solid state devices: a LIS cell and an n-channel ISFET. Ta2O5 with different electrical and optical properties and crystalline structures were applied to both devices for an inspection of the relation between those properties and ion-sensitive properties. No substantial influence of the electrical properties of the films was found on the ion-sensitive properties. A crystalline transformation of the Ta2O5 film from an amorphous to a polycrystalline state by thermal annealing did not immediately effect the ion-sensitive properties however, aging tests showed it drastically reduced the film lifetime.