Deposition and characterisation of shear-mode ZnO sensor and micro-cantilever for contact sensing and nanoactuation

• Optimal sputtering working condition for zinc oxide thin film deposition was identified
• The fabricated ZnO thin film-based sensor arrays are able to detect contact force
• The fabricated micro-cantilever with shear mode ZnO thin film sensor displays piezoelectric effect.

Integrated sensors in fitness and sports equipment have been developed in the last two decades. A zinc oxide (ZnO) thin film could be a suitable material for such applications due to its excellent physical and piezoelectric properties. In this paper, nanocrystalline ZnO films were deposited on silicon (Si) wafers with different substrate tilt angles (30° to 75°) and sputtering durations (2 to 4 h) using RF magnetron sputtering at room temperature. ZnO thin film topographical properties, film thickness (0.8 to 3.7 μm) and columnar inclined angle (14° to 34°) on the different locations of specimens were characterised by scanning electron microscope (SEM). Simulation and experimental results from the sensor arrays were also fabricated using fabrication techniques compatible with a standard micromachining process. The simulation and experiments for sensor arrays proved that sensor arrays were capable of distinguishing the differences of contact force values, contact locations and directions. Moreover, ZnO thin film micro-cantilevers were fabricated and tested by an AC impedance technique and a laser doppler vibrometer (LDV). The results exhibited good piezoelectric properties of shear-mode ZnO thin film driven cantilevers.

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