Determination of the diffusion coefficient of proton in CVD gamma aluminum oxide thin films

Proton diffusion in aluminum oxide thin films is of significant interest because of its importance in barrier, sensor and catalytic coating applications. In this study, a novel method based on potential-pH response measurement was used to determine proton diffusivity in CVD produced gamma aluminum oxide thin films. This technique based on the model of diffusion-controlled transport at the oxide surface, measures the potential-pH response drift as a stepwise increase and decrease in pH (i.e. pH 4 and 7) with a thermostatic measurement set-up. The drift in the potential-pH response is believed to be due to the surface layer, which affects proton diffusion onto the oxide film of the Al2O3-gate ion selective field effect transistor. The diffusion coefficient of proton in aluminum oxide thin film using the potential-pH response method was 6.5×10−18 cm2/s. The unique feature of this method is its relatively simple experimental procedure, which eliminates complications arising from surface related effects and/or presence of hydrogen traps in the metal, also offers a considerable reduction in test time with the experiment being completed in 10 h as compared to the conventional electrochemical permeation method which takes as long as 5 days.