ZnO:Na纳米晶室温表面光电压气敏机理的研究

Gas sensing mechanism of ZnO:Na nanocrystals at room temperature using surface photovoltage spectroscopy

采用简单溶胶凝胶法在溅射有Au/Ti叉指电极的PET柔性基底上制备出不同Na掺杂浓度的ZnO纳米晶。通过对样品的微结构和光学性质表征,探究光辅助室温NO_(2)气敏机理与表面光电压之间的联系。X射线衍射(XRD)结果显示所有样品均为六方纤锌矿结构,Na的掺杂并没有出现Na及其氧化物的衍射峰。室温气敏测试结果显示Na掺杂ZnO纳米晶具有优良的室温气敏性能,能够检测到0.94 mg/m^(3)浓度的NO_(2),相对于纯ZnO纳米晶体气敏响应明显提高。表面光电压谱(SPV)和紫外可见分光光度计(UV-Vis)实验结果表明掺杂ZnO样品的室温气敏性可能与其表面缺陷含量和缺陷能级有关。Na掺杂能够显著增强光生电荷的分离,同时也引入了更多的氧空位(Vo)和活性位点,促进了NO_(2)气体与表面吸附电离氧缺陷的反应。另外光学带隙的蓝移和新产生的缺陷能级也进一步提高了对NO_(2)气体的灵敏度。

ZnO nanocrystals with different Na doping concentrations were prepared on PET flexible substrates sputtered with Au/Ti interdigital electrodes by a simple sol gel method.The relationship between the photoassisted room temperature NO_(2) gas sensing mechanism and surface photovoltage was explored by characterizing the microstructure and optical properties of the sample.The X-ray diffraction(XRD)results show that all samples have the hexagonal wurtzite structure,and Na doping does not exhibit diffraction peaks of Na and its oxides.The room temperature gas sensitivity test results show that Na doped ZnO nanocrystals have excellent room temperature gas sensitivity performance,and 0.94 mg/m^(3) NO_(2) is detected,which significantly improves the gas sensitivity response compared to pure ZnO nanocrystals.The experimental results of surface photovoltage spectroscopy(SPV)and ultraviolet visible spectrophotometer(UV-vis)indicate that the room temperature gas sensitivity of doped ZnO samples may be related to their surface defect content and defect energy levels.Na doping can significantly enhance the separation of photo generated charges,while also introducing more oxygen defects(Vo)and active sites to promote the reaction between NO_(2) gas and surface adsorbed ionized oxygen defects.In addition,the blue shift of the optical bandgap and the newly generated defect energy levels further enhance the sensitivity of NO_(2) gas.