Oxygen vacancy (V_O) is long believed as a key factor influencing the gas sensing properties. However, the concentration of V_O is generally focused while the V_O state is neglected, which masks the inherent mechanism of gas sensor. Using a post annealing process, the influence of V_O states on the response of ZnO nanofilm to NO₂ gas is investigated in this study. The systematical analysis of the results obtained by different methods indicates a transformation of V_O from the neutral to the doubly ionized state during post annealing treatment. The results also imply that the gas sensing properties is not directly correlated with the V_O concentration. And due to the competitive adsorption of ambient O₂, the neutral V_O is majorly occupied by the adsorbed O₂ while the V_O in doubly ionized state can promote the adsorption of NO₂. Consequently, the transition of V_O from the neutral to the doubly ionized state can lead to a dramatic increase of the response to NO₂, from 733 to 3.34 × 10⁴ for 100 ppm NO₂. Guided by this mechanism, NO₂ gas sensing in ppb-level is also achieved: the response reaches 165% to 25 ppb (0.025 ppm) NO₂ with a good repeatability.

长期以来，氧空位 (V _O ) 被认为是影响气体传感特性的关键因素。然而，通常只关注VO的浓度而忽略VO的_状态，掩盖了气体传感器的内在机理。本研究采用后退火工艺，研究了 V _O状态对 ZnO 纳米薄膜对 NO ₂气体响应的影响。对通过不同方法获得的结果进行系统分析表明，在后退火处理过程中，V _O从中性状态转变为双电离状态。结果还表明，气敏特性与 V _{O不直接相关}专注。并且由于环境O ₂的竞争吸附，中性V _O主要被吸附的O ₂占据，而处于双电离状态的V _O可以促进NO ₂的吸附。因此，VO 从中性态到双电离态的转变_{可导致对 NO 2}的响应显着增加，对于 100 ppm NO ₂从 733 到 3.34 × 10 ⁴。在此机制的指导下，还实现了 ppb 级的NO _{2气体传感：响应达到 165% 至 25 ppb (0.025 ppm) NO 2}，​​具有良好的重复性。