The thickness effects on the electrical properties and microstructures of Gallium doped zinc oxide (GZO) thin films on Corning glass substrates by rf. Sputtering has been studied. The deposited GZO films at room temperature were polycrystalline with a hexagonal Wurtzite structures and preferential orientation along (0002) plane. The crystallinity and electrical conductivity of the GZO showed an increasing tendency as function of the film thickness. This indicates that the GZO film crystallity and the electrical properties are strongly affected by its film thickness. Cross-sectional TEM micrographs of 50 nm-thickness GZO film show a weakly crystalline structures response to its electrical conductivity. The resistivity of GZO prepared with around 300 nm in thickness is about 2.8×10-3 Ω-cm.
A design of experiment was taken out to study the electrical properties and surface morphology of 300 nm-thickness GZO films on polymeric PET substrate with SiO2 and TiO2 buffer layers. GZO film deposited on bare PET substrate show resistivity of about 5.1×10-2 Ω-cm, comparable to that of SiO2-coated PET (3.4×10-2 Ω-cm) and TiO2-coated PET (2.8×10-1 Ω-cm), respectively. The GZO films also show quite different surface morphology by atomic force microscopy, implying that the film growth mechanism was strongly affected by buffer layer. Hall effect measurement revealed that the increase in resistivity due to a decrease of mobility and decrease of carrier concentration when applying TiO2 buffer layer of the GZO film growth.
|