Hydrogenation-produced In₂O₃/InN core-shell nanorod and its effect on NO₂ gas sensing behavior

In this work, for the first time, we have made InN/In₂O₃ core-shell heterostructure by hydrogen plasma treatment. InN nanorods (NRs) were grown by using plasma-assisted molecular beam epitaxy, and hydrogen plasma treatment was performed by using reactive ion etching at room temperature. From x-ray photoemission spectroscopy studies, it was observed that the bonding partner of In changes from N to O and N 1s completely disappeared in the hydrogenated InN NRs. Furthermore, high-resolution transmission electron microscopy revealed the formation of InN/In₂O₃ core-shell NRs by hydrogenation plasma treatment. The resistance of pristine InN NRs was decreased in NO₂ ambient. Interestingly, the resistance of the InN/In₂O₃ core-shell was increased while introducing NO₂ gas. InN NR surface exhibits downward band bending due to the electron accumulation, in NO₂ ambient, and the surface band bending was decreased due to the increase in the bulk conduction channel. This reversed gas sensing behavior in InN/In₂O₃ core-shell NRs was attributed to the increase in depletion layer while reducing the conduction channel width by the absorption of NO₂. The InN/In₂O₃ coreshell NRs exhibited a response of 22.43% at 50 °C, which was 5.11 times higher than that of pristine InN NRs.