Abstract
Potassium ion electret technique was invented in 2012 and first reported in IIP2012. This technique is able to give a semi-permanent high bias voltage to silicon MEMS devices having high aspect ratio structures. Potassium ions are introduced by thermal oxidation process, and then evacuated from the oxide by applying a voltage with heating the device at about 550 degree. Consequently, remaining negatively charged oxide defects compose a space charge region in the oxide and make a electret potential. This technique has been applied to vibration energy harvesters made of a silicon wafer and showed ability of power generation with very low acceleration and wide-band frequency response.
