The Impact of $\hbox {TiO}_{2}$ Interface Layer on a Pd/n-LTPS Schottky Diode Hydrogen Detecting Performances

The hydrogen detecting performances of Pd/n-LTPS Schottky diodes, with and without a TiO₂ interface layer fabricated on glass substrates, were studied in detail. The n-LTPS film, an n-type low-temperature prepared polysilicon film, is formed by annealing an amorphous silicon (a-Si) thin film with excimer laser and treated by PH₃ gas plasma. With the TiO₂ interface layer, the hydrogen response (Sr) of the n-LTPS Schottky diode under room temperature and -2-V bias is promoted from 331.5% to 3504% in 8000 ppm H₂/air ambient, which is comparable to the reported low cost H₂ sensor based on bulk Si or III-V compound material. The hydrogen response promotion with the addition of the TiO₂ layer is attributed to the suppression of the interface Fermi level pining issue and the increases of hydrogen adsorption activity.