Observation of Surface Potential of Micropatterned Self-assembled Electrets for MEMS Vibrational Energy Harvesters.

In this paper, we present the observation results of the surface potential of micropattemed thick (> 1 pm) self-assembled electrets (SAEs) for MEMS vibrational energy harvesters (VEHs). To evaluate the surface potential of micropattemed SAEs, we propose and develop test devices with removable through-hole substrates corresponding to the moving electrodes of SAE-MEMS VEHs. In this study, SAEs are deposited simultaneously on two test devices with different through-hole spacings and on a reference flat substrate using the same vacuum evaporation process. The surface potential of SAEs is proportional to the film thickness, and when the film thickness of the SAE deposited on the flat substrate is 4.48 pm, the surface potential exceeds 200 V. At this time, in a test device where the average thickness of micropattemed SAEs is 3.08 pm, the measured surface potential is 68 V. In addition, it is experimentally observed that when micropattemed SAEs are formed using the through-hole structures, the microfabrication process causes the SAE pattern to spread wider than the through-hole dimensions, and the surface profiles are not flat. These findings provide useful insights for the design of SAE-MEMS VEHs using micropattemed SAEs with through-hole structures. [ABSTRACT FROM AUTHOR]