Comparison of DC and RF sputtered aluminium-doped zinc oxide for photovoltaic applications

AZO was sputter deposited using both RF and DC power supplies from a pre-formed ceramic AZO target with a 2 wt % aluminium oxide dopant concentration. The target was formed by hot pressing pre-doped nanoparticles produced using an emulsion detonation synthesis technique. AZO films were found to display good optical and electrical properties regardless of deposition technique. Increased temperatures above 200 °C were found to have a negative impact on the electrical properties, with a corresponding increase in infrared transmission. Visible transmission was found to be good (above 79 %) for all films except those deposited using DC power at room temperature. The DC sputtering process was stable and was found to approximately double the deposition rate with no corresponding drop in film quality for films deposited at moderate temperatures. This makes DC deposition more industrially attractive when process temperature is not a concern. For room temperature depositions, RF was found to produce superior transmission and electrical characteristics.