PD NI-AL2O3-AL TUNNEL-DIODE AS HIGH-CONCENTRATION-HYDROGEN GAS SENSOR/

Pd/Ni-Al2O3-Al tunnel diodes were fabricated on a glass substrate for detection of high-concentration hydrogen gas. For Pd-Al2O3-Al diodes, the output signals were saturated at hydrogen partial pressures higher than approximately 0.1 Torr, whereas a Pd/Ni(22%)-Al2O3-Al diode show ed output signals even at, 50 Torr hydrogen partial. pressure at room temperature. The concentration oi hydrogen detectable with the Pd/Ni a lloy metal insulator-metal (MIM) diodes increased with an increase in the Ni content. The change in the barrier height at the Pd/Ni-Al2O3 in terface upon introduction of hydrogen gas tvas also measured for vario us Ni contents in Pd/Ni alloys by means of the logarithmic derivative of the tunnel current and was found to be associated with the hydrogen sensitivity of the Pd/Ni alloy MIM junctions.