High Surface Potential Lanthanum Aluminate Electret Thin Film for Vibrational Energy Harvesting Devices

The highest surface potential with reflow process compatibility was achieved using lanthanum aluminate (LAO) as an electret thin film deposited by atomic layer deposition (ALD), a technique capable of coating high-aspect-ratio features. The surface potential was improved to -1077 V, about twice the previously reported surface potential of silicon dioxide electret thin films for micro electromechanical systems (MEMS) devices [1]. Even after heating at 260 degrees C for 30 minutes to simulate the reflow process, the surface potential remained at -935 V. In addition, this high surface potential electret was applied to a vibrational energy harvesting device, achieving a normalized power density of 5.35 mW/cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup>/G<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> with a broad full width at half maximum (FWHM) of 64 Hz, representing superior characteristics compared to those reported previously [2]–[4].