カリウムイオンエレクトレットにおける負電荷蓄積機構の第一原理計算による検討

抄録

A potassium-ion electret, which is a key element of vibration-powered microelectromechanical generators, is a material that permanently stores negative charge. However, the charge storing mechanism of a potassium-ion electret is still unclear. In this study, we theoretically study the atomic and electronic structures of amorphous SiO₂ with and without potassium atoms using first-principles molecular-dynamics calculations. As a result of calculations, we confirmed the existence of a fivefold-coordinated Si atom with five Si-O bonds as a characteristic local structure in a-SiO₂ with potassium atoms, which is negatively charged. This result indicates that the fivefold-coordinated Si structure is the physical origin of the negative charge observed in potassium-ion electret. Furthermore, we show the guidelines for the experimental observation of the fivefold-coordinated structure and the fabrication of high-reliability potassium-ion electret.