Effect of Thickness of SnO2:F over Layer on Certain Physical Properties of ZnO:Al Thin Films for Opto-electronic Applications

Bilayered FTO/AZO (fluorine doped tin oxide/aluminium doped zinc oxide) films were fabricated using a simple, cost effective spray pyrolysis technique. X-ray diffraction (XRD) profiles of bilayered films showed that in the case of lower thickness FTO over layers, (002) plane of ZnO phase had the highest intensity, whereas the predominance was changed in favour of (200) plane of SnO2 phase for higher thickness FTO over layer. UV studies showed that bilayered FTO/AZO films exhibited a sharp absorption edge as that of AZO film. The decrease in the photoluminescence (PL) peak at 420 nm with increasing FTO over layer thickness indicated a reduction in the zinc vacancies which caused a reduction in the sheet resistance (Rsh). Electrical studies revealed that, eventhough the Rsh value (916 Ω/□) of bilayered FTO (313 nm)/AZO (314 nm) film was found to be higher than that of FTO single layer film (72 Ω/□), it was much lower than that of AZO single layer film (5661 Ω/□). The atomic force microscopy (AFM) images reflect the characteristic features of both zinc oxide and tin oxide films.