The Effects of Critical Sputtering Parameters on Aluminum Zinc Oxide Thin Films for Transparent Conducting Oxide Applications
Transparent conducting oxides (TCOs) are materials exhibiting electrical conductivity with high transparency of electromagnetic waves within the visible region of the spectrum. TCOs are usually prepared with thin film technologies and used in opto-electrical applications such as solar cells, displays, OLEDs and energy efficient windows. For decades, Indium Tin Oxide (ITO) was superior; however, Indium is rare and expensive. An alternative to ITO is Aluminum doped zinc oxide (AZO). Its thermal stability, affordability, and abundance give AZO a significant advantage over ITO. It is the aim of this work to obtain a low resistive AZO thin film with good transparency in order to better understand how dominant sputtering variables affect the properties of AZO for TCO applications.
Highly oriented, in the (002) direction, AZO thin films were prepared on a glass substrate using the RF magnetron sputtering technique. The films were deposited at various substrate temperatures and RF power values. X-ray diffraction was used to identify phases. Surface analysis of the film was carried out using Atomic Force Microscopy. The resistivity was calculated using 4-point Probe technique and optical transmittance was measured using UV spectrophotometer. All ZnO:Al films grown showed optical transmittance on average between 80-90% percent in the visible region and a small part of the near infrared region of the spectrum. The resistivity ranged from 1.3e-3 Ω.cm to 2.95e-3 Ω.cm.
As TCO technology evolves, there will be greater demand for higher conductive films with a larger transparency spectrum. AZO is a viable candidate for fulfilling that need