抄録
We report a SiO_2 electret for comb-drive actuators that do not need to apply a driving voltage. A Si wafer was oxidized in a electric furnace where potassium ions are injected by bubbling of KOH solution using nitrogen gas (N_2). The thickness of SiO_2was 500 nm. This SiO_2 film with potassium ions was polarized by the bias-temperature (B.T.) treatment. When the B.T. treatment voltage was -35 V and the temperature was 200 ℃, the initial surface potential was 10.3 V. This value was gradually dropped at 8.6 V five hours later. The decrease is assumed to settle down in 7.6 V by the calculation. This value is sufficient to drive comb actuators.
