Current vs voltage characteristics of Al-Al2O3-Pd tunnel junction hydrogen sensor

The conduction mechanism of an Al-Al2O3-Pd MIM (metal-insulator-metal) junction which can operate as a hydrogen gas sensor tvas investigated using the logarithmic derivative of the current curve, Fowler-Nordheim plot and temperature dependence of the junction current. Al-Al2O3-Pd junctions showed current-voltage characteristics typical of tunneling conduction at voltages above 3 V. The barrier height of the Pd-Al2O3 contact obtained from the position of the logarithmic derivative maximum of the current was 3.4 eV in vacuum, and decreased to 2.7 eV upon introduction of 40 Pa hydrogen. On the other hand; the barrier height of the Al-Al2O3 contact was 1.8 eV in vacuum and was unchanged even when 40 Pa of hydrogen gas was introduced.