Ultra high-sensitive, prompt response and recovering Pt/(Pt+SiO2) cermet layer/GaN-based hydrogen sensor for life-saving applications

Abstract

In this work, we report an ultra-high sensitive (S = 1.4 × 108%), prompt response and recovering Pt/Pt+SiO2 cermet layer/GaN-based hydrogen (H2) sensor. A sensor fabricated with a 15 nm cermet layer, comprising Pt and SiO2, deposited between 15 nm Pt and GaN layers, exhibits significantly enhanced sensitivity in the detection of 4 %H2 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 () reducing from 1.4 × 108% to 2.3 × 107% as temperature increases from 300 to 423 K. The shift in the threshold voltage of the test sensor (ΔVt,test = 767 mV) increases by 50 % as compared to the shift in threshold voltage of the control sensor (ΔVt,control = 511 mV) at 1 mA/cm2. 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 (), response (τa) and recovery (τb) times of the test sensor when exposed to 10 000 ppm of H2 are 3.9 × 107%, 30 secs and 30.1 secs respectively. The shift in the threshold voltage of the test sensor at 1 mA/cm2 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+SiO2 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+SiO2 cermet-based sensor, with its response and recovery times in the order of milliseconds for a temperature range of 363–423 K.