Room temperature hydrogen gas sensor based on Pd decorated bridging GaN nanowires

A highly sensitive and low-power consumption hydrogen (H2) gas sensor based on palladium nanoparticles (Pd NPs) decorated bridging GaN nanowires (NWs) has been fabricated, which can be used for H2 detection at room temperature (RT). The bridging GaN NWs growth across the deep trench of GaN coated sapphire substrate were prepared by Metal-organic Chemical Vapor Deposition (MOCVD), and Pd NPs were deposited on the surface of GaN NWs using magnetron sputtering. The characterizations of the structure and morphology of Pd-GaN NWs indicated that the Pd NPs were successfully loaded on the surface of GaN NWs. The sensors with different Pd thickness (2 nm, 5 nm, 10 nm, and 15 nm) were measured at RT (∼ 25 ℃), with H2 concentrations varying from 1 to 10,000 ppm. When the Pd thickness is 10 nm, the H2 response reaches its maximum, has a fast response time (∼3 s toward 10,000 ppm H2) and a low detection limit (LOD) of 42.2 ppb H2. Moreover, the sensor has excellent repeatability, superior H2 selectivity, relatively good humidity-tolerant and long-term stability. In addition, H2 sensing characteristics at different self-heating power (1.9 mW, 6.6 mW, 18.4 mW, and 36.1 mW) were also measured, and found that the H2 response increased with the increase of self-heating power. The fabricated H2 sensor with low-power consumption (without heater or illumination) have a wide application in portable device or Internet of Things (IoT) system.