Thin-Film Engineering of Mechanical Fragmentation Properties of Atomic-Layer-Deposited Metal Oxides

Mechanical fracture properties were studied for the common atomic-layer-deposited Al₂O₃, ZnO, TiO₂, ZrO₂, and Y₂O₃ thin films, and selected multilayer combinations via uniaxial tensile testing and Weibull statistics. The crack onset strains and interfacial shear strains were studied, and for crack onset strain, TiO₂/Al₂O₃ and ZrO₂/Al₂O₃ bilayer films exhibited the highest values. The films adhered well to the polyimide carrier substrates, as delamination of the films was not observed. For Al₂O₃ films, higher deposition temperatures resulted in higher crack onset strain and cohesive strain values, which was explained by the temperature dependence of the residual strain. Doping Y₂O₃ with Al or nanolaminating it with Al₂O₃ enabled control over the crystal size of Y₂O₃, and provided us with means for improving the mechanical properties of the Y₂O₃ films. Tensile fracture toughness and fracture energy are reported for Al₂O₃ films grown at 135 °C, 155 °C, and 220 °C. We present thin-film engineering via multilayering and residual-strain control in order to tailor the mechanical properties of thin-film systems for applications requiring mechanical stretchability and flexibility.