Identification of electrical properties in individual thickness layers in aluminium-doped zinc oxide films sputtered at 100 °C

This work presents a detailed study of aluminium-doped zinc oxide thin films sputtered at 100 degrees C, with a focus on the correlation between structural and electrical properties. The structural properties are identified by SEM microscopy and X-ray diffraction, while the electrical properties are described by means of the carrier concentration and the carrier mobility, both determined experimentally. The study consists of a set of thin films with thicknesses from similar to 16 to similar to 1120 nm. Our analysis shows that the electrical properties in each individual thickness layer gradually change with its distance from the substrate, which correlates very well to the changes observed in structural properties. Along with our experimental findings, we have designed a one-dimensional mathematical model based on the trapping states related to the grain boundaries. This model offers a deeper insight into the relation between the film structure and the film resistivity and allows identification of additional material characteristics such us the trap density at the grain boundary.