Spatially Resolved Optoelectronic Properties of Al-Doped Zinc Oxide Thin Films Deposited by Radio-Frequency Magnetron Plasma Sputtering Without Substrate Heating

Transparent and conducting thin films were deposited on soda lime glass by RF magnetron sputtering without intentional substrate heating using an aluminum doped zinc oxide target of 2 inch in diameter. The sheet resistance, film thickness, resistivity, averaged transmittance and energy band gaps were measured with 2 mm spatial resolution for different target-to-substrate distances, discharge pressures and powers. Hall mobility, carrier concentration, SEM and XRD were performed with a 3 mm spatial resolution. The results reveal a very narrow range of parameters that can lead to reasonable resistivity values while the transmittance is much less sensitive and less correlated with the already well-documented negative effects caused by a higher concentration of oxygen negative ions and atomic oxygen at the erosion tracks. A possible route to improve the thin film properties requires the need to reduce the oxygen negative ion energy and investigate the growth mechanism in correlation with spatial distribution of thin film properties and plasma parameters.