A differential capacitive thin film hydrogen sensor

A compact, differential, hydrogen-specific sensor based on the lattice expansion of LaAl_0.3Ni_4.7 metal hydride thin films has been fabricated and characterized. Characterization of LaAl_0.3Ni_4.7 films performed using a capacitance dilatometer revealed that the lattice expansion was proportional to the partial pressure of H₂ over the range 0.01–1.3 atm used in this experiment. The films were mechanically robust to cycling between vacuum and partial pressures of H₂ up to 1.3 atm and were not poisoned by exposure to atmosphere's containing up to 24% carbon monoxide. A wafer level process has been established for the fabrication of the differential hydrogen sensor which includes both an active LaAl_0.3Ni_4.7 sensing capacitor and an inert Au reference capacitor. A minimum sensitivity of 400 ppm hydrogen is calculated for the differential device.