Al-doped ZnO thin film enhancing the photo-catalytic bactericidal performance on the (100) plane of ZnO single crystal

Abstract In this paper, the different photo-catalytic bactericidal activity of three types ZnO materials (m plane (100) [1,2] , of ZnO single crystal (ZnO SC), Al-doped ZnO thin films on m plane of ZnO single crystal (AZO-SC) and Al-doped ZnO thin films on glass (AZO-G)) were investigated. XRD and AFM analysis showed that the AZO thin films grown on ZnO (100) plane still followed the (100) growth direction of the ZnO SC substrate, and the ultimate morphology appeared as an island structure. When deposited on glass, the AZO thin films appeared (002) diffraction peak. The counting of the re-grown bacterial colonies of Escherichia coli and Bacillus subtilis after photo-catalytic action showed the photo-catalytic bactericidal activity followed by the order of AZO-SC > ZnO SC > AZO-G. Further confocal laser scanning microscopy (CLSM) and AFM images indicated that free radicals are likely to attack the bacterial cell wall firstly, then the cell membrane, eventually leading to the death of bacteria during the photo-catalytic process. The interfacial electric field (IEF) formed between the AZO thin films and ZnO SC was believed to be responsible for the significant improvement of photo-catalytic activity of the ZnO single crystal.