From glass to cobalt oxide: investigating ZnO thin film characteristics

Abstract In this study, we investigated the properties of ZnO thin films deposited on glass and a cobalt oxide (Co 3 O 4 ) layer. The films were produced using the spray pyrolysis technique and analyzed through various methods. X-ray diffraction results confirmed the formation of Co 3 O 4 and ZnO in both cases—on glass and on the Co 3 O 4 layer. The crystallite sizes for all layers were estimated using Scherrer’s equation, revealing that the Co 3 O 4 layer had a crystallite size of 16.7 nm, while the ZnO layer on glass exhibited a crystallite size of 13.7 nm. An increase in crystallite size was observed for the ZnO layer on Co 3 O 4 , which measured 14.6 nm. Field emission scanning electron microscopy images of the Co 3 O 4 surface showed the presence of fine grains, predominantly with triangular shapes. The ZnO layer deposited on glass displayed irregular grains with an average size of 134.4 nm, whereas the ZnO layer on the Co 3 O 4 substrate had an average grain size of 111.7 nm. The UV sensing properties of both ZnO layers were evaluated under UV light at 365 nm, revealing a significant reduction in decay time, although it remained relatively long.