Highly hydrogen sensitive micromachined sensors based on aerosol-assisted chemical vapor deposited ZnO rods

Chemoresistive gas microsensors with highly hydrogen sensitive zinc oxide rods dominated by exposed {100} surfaces are fabricated. The hexagonal rod structures are integrated into micromachined transducing platforms without the need for substrate pre-treatment, via a vapor-solid mechanism enabled using an aerosol-assisted chemical vapor deposition method. The microsensors demonstrate an enhanced functionality towards hydrogen, with greater sensor responses (between 200% and 1800%) compared to other gases including ethanol, carbon monoxide, acetone, and toluene, and with low interferences among these reductive gases. The improved functionality of these systems towards hydrogen is attributed to the formation of an accumulation layer at the zinc oxide rods after hydrogen exposure, which includes a mechanism not only dominated by the oxygen vacancies, but also by the formation of intermediate energy levels for the transfer of charge from hydrogen to the zinc oxide conduction band.