Generation of nanogaps on porous ZnO sheets via Li-ion implantation: NO2 gas sensing with ultrafast recovery time

Abstract

Nanoscale defect structures on material surfaces introduce diverse chemical physics and have received sub-stantial attention. However, nano structure distortions due to low stability and poor reproducibility have indi-cated the limitation for further electro-device applications using defect control. In this study, the higher activated electron transfer from the nanogaps (NGs) enhances the sensitivity and accelerated depletion region purifying the porous-ZnO (P-ZnO) sheets for NO2 gas-sensor applications.-2.2 nm width of NGs on the (1010) orientated P-ZnO sheets and 12% higher surface oxygen vacancies (VO) are formed by using Li-ion implantation via the lithiation process. This intrinsic electron-doped ZnO by NGs shows a reduced work function (phi) and an elevated Fermi level (EF) compared to pristine ZnO. Therefore, the reaction between NO2 gas and ZnO significantly ac-celerates owing to the activated electron transfer that carries ultrafast recovery time (-16 s), and a low limit of detection (-4 ppb) at 150 celcius are obtained for the NG-P-ZnO sheet-based gas sensor. The generation of NGs on the surface via Li-ion implantation with reliable stability provides a new strategy to improve the electrochemical reactivity of semiconducting metal oxides beyond that obtained using conventional material engineering ap-proaches, such as size, shape, and dimension control.