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

Abstract

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.