Feather-Shaped InGaN Nanorods for Selective ppb-Level Detection of NO₂ Gas at Room Temperature

Materials with peculiar nanostructures enclosing the surface play a pivotal role in a variety of applications, especially gas-sensing applications, due to their high surface-to-volume ratio. In this study, we tailored the nanorod (NR) morphology of InGaN into various unusual shapes such as bud, mace, and feather shapes and investigated the gas-sensing abilities of these structures. Remarkably, tuning the NR morphology significantly enhanced the NO2 gas response, with the feather-shaped morphology showing the best performance. The feather-shaped InGaN NRs displayed a response of 72.64% to 100 ppm NO2 gas, which is not only four times that of pristine InGaN NRs but also the highest response so far compared to that among state-of-the-art InGaN- or GaN-based NO2 gas sensors. Furthermore, photon-assisted sensing stimulated the responses of feather-shaped InGaN NRs, with the limit of detection extending to 200 ppb (6.12%). In addition, feather-shaped InGaN NRs were more selective to NO2 gas than to other target gases such as H2S, H2, NH3, and CO. The growth mechanisms of the different morphologies, as well as their enhanced NO2 gas responses, were successfully demonstrated. This morphology engineering strategy can be extended to design III-nitrides of different shapes for excellent gas-sensing applications.