Abstract
Herein, the fabrication of a novel highly sensitive and fast hydrogen (H2) gas sensor, based on the Ta2O5 Schottky diode, is described. First, Ta2O5 thin films are deposited on silicon carbide (SiC) and silicon (Si) substrates via a radio frequency (RF) sputtering method. Then, Pd and Ni are respectively deposited on the front and back of the device. The deposited Pd serves as a H2 catalyst, while the Ni functions as an Ohmic contact. The devices are then tested under various concentrations of H2 gas at operating temperatures of 300, 500, and 700 °C. The results indicate that the Pd/Ta2O5 Schottky diode on the SiC substrate exhibits larger concentration and temperature sensitivities than those of the device based on the Si substrate. In addition, the optimum operating temperature of the Pd/Ta2O5 Schottky diode for use in H2 sensing is shown to be about 300 °C. At this optimum temperature, the dynamic responses of the sensors towards various concentrations of H2 gas are then examined under a constant bias current of 1 mA. The results indicate a fast rise time of 7.1 s, and a decay of 18 s, for the sensor based on the SiC substrate.
Highlights
Hydrogen (H2 ) gas detection is widely used in various fields such as environmental monitoring, domestic/industrial safety control, seismic surveillance, semiconductor technology, and chemical/industrial process control.the colorless, odorless, and toxic nature of hydrogen gas renders it undetectable by the human eyes or nose, while its readily diffusive, highly flammable, corrosive, and explosive nature can result in disastrous consequences in the event of a leakage
These results are significantly better than those previously reported for H2 sensors [35,36] and suggest that the Pd/Ta2 O5 /silicon carbide (SiC)-based Schottky diode is a promising candidate for H2 sensing applications
The results indicated that the SiC-based Pd/Ta2 O5 Schottky diode is much more sensitive than the Si-based device towards H2 gas at high operating temperature
Summary
Hydrogen (H2 ) gas detection is widely used in various fields such as environmental monitoring, domestic/industrial safety control, seismic surveillance, semiconductor technology, and chemical/industrial process control (e.g., in nuclear reactors and coal mines). A significant drawback in the use of Pd metal as a highly-sensitive hydrogen detector is the strong tendency for its electrical resistance to exhibit hysteresis due to the facile adsorption of hydrogen into the Pd structure [20,21] In view of these challenges, recent research is focusing on the replacement of metal oxide-based materials to achieve high sensitivity and selectivity along with a higher response under a range of working H2 concentrations, as well as improved cost effectiveness and reproducibility. The results indicate an optimum operating temperature of 300 ◦ C and, under this optimum condition, the Ta2 O5 /SiC-based sensor performs exceptionally well, showing excellent sensitivity along with fast rise and fall times of 7 s and 18 s, respectively These results are significantly better than those previously reported for H2 sensors [35,36] and suggest that the Pd/Ta2 O5 /SiC-based Schottky diode is a promising candidate for H2 sensing applications. To the best of the present authors’ knowledge, few reports on a Pd/Ta2 O5 /SiCbased Schottky diode aimed at H2 gas sensing have been published [37,38,39]
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