Giant Blistering of Nanometer-Thick Al 2 O 3 /ZnO Films Grown by Atomic Layer Deposition: Mechanism and Potential Applications.

Giant circular blisters of up to 300 μm diameter and 10 μm deflection have been produced on nanometer-thick Al2 O3 -on-ZnO stacks grown by atomic layer deposition at 150 °C followed by annealing at elevated temperatures. Their shape changes upon varied ambient pressures provide evidence that their formation is related to an anneal-induced outgassing combined with their impermeability. The former mainly occurs in the bottom ZnO layer that recrystallizes and releases residual hydroxide ions at elevated temperatures while the latter is dominantly contributed by the pinhole-free Al2 O3 layer on top. Vibrations at a resonant frequency of ∼740 kHz are mechanically actuated and optically probed from an individual blister. By modulating the thickness and stacking sequence of Al2 O3 and ZnO, we further demonstrate a localized circular film swelling upon electron-beam irradiation and its recovery after reducing the irradiation flux. The elastic blistering and the recoverable swelling of the nanometer-thick films represent a miniaturized event-driven mechanical system for potential functioning applications.