We have proposed a hydrogen detection sensor based on a Pd (palladium)-coated, single-mode, optical fiber. The experimental results demonstrated that the sensor could detect hydrogen in air as well as in insulation oil. The influence of Pd film thickness and environmental temperature on response time and sensitivity was analyzed. The reflected optical power at the optical-fiber/Pd interface decreased as the concentration of hydrogen increased, in both air and the insulation oil. The sensor showed 0.75 dB of optical power variation when the concentration of dissolved hydrogen was saturated in the insulation oil.

We investigated a SiC-based hydrogen gas sensor with MIS (metal-insulator-semiconductor) structure for high temperature applications. The sensor was fabricated by Pd/TiO₂/SiC structure, and a thin titanium dioxide (TiO₂) layer was exploited for sensitivity improvement. In the experiment, dependences of I-V characteristics and capacitance response properties on hydrogen gas concentrations from 0 to 2,000 ppm were analyzed at room temperature to 400℃. As the result, our sensor using TiO₂ dielectric layer showed possibilities with regard to use in hydrogen gas sensors for high-temperature applications.

We investigated a SiC-based hydrogen gas sensor with metal-insulator-semiconductor (MIS)structure for high temperature process monitoring and leak detection applications. The sensor was fabricated by Pd/Ta2O5/SiC structure, and a thin tantalum oxide (Ta2O5) layer was exploited with the purpose of sensitivity improvement, because tantalum oxide has good stability at high temperature as well as high permeability for hydrogen gas. In the experiment, dependence of I-V characteristics and capacitance response properties on hydrogen gas concentrations from 0 to 2,000 ppm was analyzed at room temperature to 500℃. As the result, our sensor exploiting a Ta2O5 dielectric layer showed possibilities with regard to use in hydrogen gas sensors for high-temperature applications.