Charge Distribution and Stability of SiO₂ Nanoarray Electret

The devices based on SiO₂ electret have significant applications in various MEMS sensors. However, the charge stability of SiO₂ electret suffered from the water percolation, which seriously restricts its application. In this work, the long-term charge stability of the SiO₂ nanoarray electret (SiO₂ NAE) without any water repellent treatment is demonstrated. When the oxidation time is 1.5 h, the potential decay of the SiO₂ NAE is less than 46% during 60 days with an original potential of −120 V. The long-term charge stability of the SiO₂ NAE is attributed to its unique charge decay process and the large H₂O diffusion barrier in the SiO₂ NAE: firstly, the charge trapped in the planar part of the SiO₂ NAE decays rapidly. Then, residual charge stored in the SiO₂ nanoarray. Eventually, the large H₂O diffusion barrier in the interface of Si/SiO₂ effectively hinders the charge decay. In addition, we demonstrate the unique charge stability of nanoelectret, which has a promising application in developing high performance electret-based devices.