Calibration and characterization of wide range hydrogen sensors

Crucial to the successful implementation of hydrogen sensing devices is the basic ability to quantitatively relate hydrogen concentration to the time-dependent electrical signals originating from the sensing structures, i.e. the sensor must be calibrated. A simple technique is developed for calibrating the resistor sensing structure for time-varying thermal environments and hydrogen concentrations in excess of approximately 1%. A procedure to achieve equilibrium calibration of the transistor for hydrogen concentrations less than approximately 1% is also presented. The rate limiting mechanisms governing the time-dependent response of the transistor are investigated. The evolution of hydrogen out of the transistor structure is shown to be thermally activated, and has been accurately modeled for a wide range of time-dependent thermal environments.