Abstract
Hydrogen has attracted attention as an alternative fuel source and as an energy storage medium. However, the flammability of hydrogen at low concentrations makes it a safety concern. Thus, gas concentration measurements are a vital safety issue. Here we present the experimental realization of a palladium thin film cantilever optomechanical hydrogen gas sensor. We measured the instantaneous shape of the cantilever to nanometer-level accuracy using diffraction phase microscopy. Thus, we were able to quantify changes in the curvature of the cantilever as a function of hydrogen concentration and observed that the sensor’s minimum detection limit was well below the 250 p.p.m. limit of our test equipment. Using the change in curvature versus the hydrogen curve for calibration, we accurately determined the hydrogen concentrations for a random sequence of exposures. In addition, we calculated the change in film stress as a function of hydrogen concentration and observed a greater sensitivity at lower concentrations.
Highlights
Hydrogen has always been viewed as a promising alternative to fossil fuels, and it can function as an effective energy storage medium for intermittent energy sources
Hydrogen is used in a range of other industries, including chemical production, metal refining, and food processing
metal oxide semiconductor (MOS)-based devices have been used as hydrogen sensors, such as MOS field-effect transistors (FETs)[6,7], high electron mobility transistors[8,9,10], and Schottky diode-type FETs11,12
Summary
Hydrogen has always been viewed as a promising alternative to fossil fuels, and it can function as an effective energy storage medium for intermittent energy sources. MOS-based devices have been used as hydrogen sensors, such as MOS field-effect transistors (FETs)[6,7], high electron mobility transistors[8,9,10], and Schottky diode-type FETs11,12. These devices require complicated fabrication processes and have high production costs. When the concentration is below the transition point for the pure β phase, the optical and mechanical properties of the Pd film will recover after hydrogen removal[13,14]. We successfully demonstrated that random hydrogen concentrations can be accurately determined using the measured curvature changes of the Pd film cantilever. We used the curvature data to extract the change in residual stress of the Pd film as a function of hydrogen concentration
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