Abrasion resistance of ZnO and ZnO:Al films on glass substrates by atomic layer deposition

Scratches and constant abrasive wear can result in zinc oxide (ZnO) and aluminum doped zinc oxide (ZnO:Al) layers that render many devices impracticable to use. Currently, the ZnO and ZnO:Al layers are widely used as transparent conductivity oxide (TCO). The top and/or bottom electrodes based on ZnO and ZnO:Al were used in organic light-emitting diodes (OLED), organic and perovskite solar cells in order to replace expensive indium tin oxide (ITO). Consequently, knowledge of the frictional properties of the ZnO layer is a necessity for many scientists. In this study, the tribological properties of zinc oxide that was formed by the Low Temperature Atomic Layer Deposition (LT ALD) method were investigated. ALD-layers (ZnO and ZnO:Al) were deposited on a glass substrates in pre-selected conditions in order to achieve films appropriate for the application of photovoltaics. The results indicate a good adhesion of the films to the substrate. The layers were abraded during friction with Al2O3 ball and their wear intensity depend on hardness of the film/substrate system. The friction coefficient of ZnO film reached value 0.1 and was higher than friction coefficient of ZnO:Al film equal 0.08. The tribological properties of these films are compared with those reported for bulk ZnO and those films deposited by sputtering.