Mechanical Properties of ZnO/Al2O3 Alloy Thin Films Deposited Via Atomic Layer Deposition

This research is motivated by the wide ranging applications for thin films, including: organic LEDs (OLEDs), flexible displays, polymers in space, and photovoltaic cells. Currently there is a need to understand the mechanical properties of such films for production and application purposes. ZnO and Al2O3 have very different properties, causing a wide range of possible properties for alloys of these materials. More specifically, this work studies the behavior of these films under tensile strain. Samples were coated with ZnO/Al2O3 alloys deposited via atomic layer deposition, then placed under tensile strain using a linear actuator. Scanning electron microscopy shows cracking occurred unilaterally and perpendicular to the applied strain.Electrical measurements were used to determine critical strain. A radioactive tracer was used to determine Al2O3 barrier performance after various strains were applied. Pure ZnO and ~95% ZnO samples show different behaviors related to thickness. The sample with the highest critical strain was an alloy of ~95% ZnO and ~100nm in thickness. Barrier performance decreased with increasing strain, as would be expected due to increased cracking which allows greater permeation. Future research will include actual thickness and crystallinity measurements. Different alloys will also be studied for more applications.