Ultra high-sensitive, prompt response and recovering Pt/(Pt+ SiO ₂ ) cermet layer/GaN-based hydrogen sensor for life-saving applications

Abstract In this work, we report an ultra-high sensitive ( S = 1.4 × 10 ⁸ %), prompt response and recovering Pt/Pt+SiO ₂ cermet layer/GaN-based hydrogen (H ₂ ) sensor. A sensor fabricated with a 15 nm cermet layer, comprising Pt and SiO ₂ , deposited between 15 nm Pt and GaN layers, exhibits significantly enhanced sensitivity in the detection of 4 %H ₂ by ≈ 300×, as compared to the reference Pt/GaN sensor at ambient temperature (300 K). Furthermore, the sensitivity of the our sensor shows very weak dependence on temperature (T) with maximum sensitivity ( {S}_max ) reducing from 1.4 × 10 ⁸ % to 2.3 × 10 ⁷ % as temperature increases from 300 to 423 K. The shift in the threshold voltage of the test sensor (Δ V _{t , test} = 767 mV) increases by 50 % as compared to the shift in threshold voltage of the control sensor (Δ V _{t , control} = 511 mV) at 1 mA/cm ² . In addition, the cermet sensor also demonstrates fast response/recovery time, which reduces from 4.58 (2.36) seconds to 94 (39) milliseconds as the temperature increases from 300 to 423 K. The maximum sensitivity ( {S}_max ), response ( τ _a ) and recovery ( τ _b ) times of the test sensor when exposed to 10 000 ppm of H ₂ are 3.9 × 10 ⁷ %, 30 secs and 30.1 secs respectively. The shift in the threshold voltage of the test sensor at 1 mA/cm ² when exposed to 100 ppm, 1000 ppm, 5000 ppm, and 10 000 ppm are 40 mV, 70 mV, 460 mV, and 600 mV, respectively. The 2-Dimensional (2D) trapping of H-atoms by the oxygen atoms present in the Pt+SiO ₂ cermet layer and porous/compact layer models explains the underlying mechanism, which results in a significant improvement of the sensing characteristics of the test sensor. The Thermionic Emission (TE) model effectively models the current density (J) - voltage (V) characteristics of both control and test sensors, with and without hydrogen. The prompt detection of high percentages of hydrogen in life-saving and commercial fuel applications becomes possible with the Pt+SiO ₂ cermet-based sensor, with its response and recovery times in the order of milliseconds for a temperature range of 363–423 K.