An In-Depth Study on Electrical and Hydrogen Sensing Characteristics of ZnO Thin Film With Radio Frequency Sputtered Gold Schottky Contacts

The electrical and hydrogen sensing characteristics of radio frequency sputtered Au/ZnO thin film Schottky diodes on n-silicon substrate have been investigated over a wide temperature range. The Current-voltage characterizations of the device in the temperature range of 25 °C to 200 °C confirm its excellent rectifying property with forward to reverse current ratio of 1610 at an external bias of 5 V. The ideality factor in the range of 4.12 to 2.98 is obtained for Au/ZnO Schottky diode in the aforementioned temperature range, at atmospheric conditions. On exposing diode to hydrogen, a reduction in the ideality factor is observed which makes thermionic emission more prominent. The proposed device has proven to be hydrogen sensitive, on account of the lateral shift observed in I-V characteristics at different hydrogen concentrations (50 ppm-1000 ppm). The maximum barrier height variation of 99 meV and sensitivity of 144% have been observed at 1000 ppm hydrogen at 200 °C. A detailed perusal of the steady-state reaction kinetics of the sensor using I-V characteristics affirmed that the atomistic hydrogen adsorption at Au/ZnO interface is accountable for the barrier height modulation. The studied sensor depicts a remarkable performance for the high-temperature detection.