Electret charging method based on soft X-ray photoionization for MEMS transducers

An electret charging method employing soft X-ray irradiation for microelectromechanical systems (MEMS) electret transducers is investigated. Soft X-rays can penetrate obstructions/narrow gaps and ionize gas molecules inside air gaps. This allows embedded electrets even after fabrication processes and vertical electrets on the sidewalls of high-aspect-ratio structures to be charged. The charging properties of polymer electrets subjected to soft X-ray irradiation were systematically examined. The surface potential of embedded electrets increased linearly with increasing irradiation time. The potential could be precisely controlled by the applied bias voltage. The surface potential of vertical electrets after charging was uniform to a depth of 20-30 times the gap opening. Since the photoionization rate depends on the collision diameter of the gas molecules with X-rays, a high charging rate was realized by using Xe gas. In the present charging method, photoionization was found to play a dominant role in generating electrons from gas molecules. Experiments performed at different gas pressures revealed that the effects of photoelectric phenomena and carrier displacement could be neglected. The present charging method was found to have a charge stability as high as that of corona charging. These results indicate that the present charging method has the potential for designing various new MEMS electret transducers.

[1]  Y. Tai,et al.  Parylene-based electret power generators , 2008 .

[2]  Toshihiro Miyata,et al.  SiO2 electret thin films prepared by various deposition methods , 2003 .

[3]  Y. Naruse,et al.  Electrostatic micro power generation from low-frequency vibration such as human motion , 2009 .

[4]  R. Gerhard-Multhaupt,et al.  Electret properties of spin-coated Teflon-AF films , 1993, Proceedings of IEEE Conference on Electrical Insulation and Dielectric Phenomena - (CEIDP '93).

[5]  Yuji Suzuki,et al.  High-speed electret charging using vacuum UV photoionization , 2011 .

[6]  Yuji Suzuki,et al.  Nano-cluster-enhanced high-performance perfluoro-polymer electrets for energy harvesting , 2011 .

[7]  M. Esashi,et al.  Charging Method of Micropatterned Electrets by Contact Electrification Using Mercury , 2005 .

[8]  B. Shore,et al.  Photoionization Processes in Gases , 1967 .

[9]  B. Gross.  Charge storage effects in dielectrics exposed to penetrating radiation , 1975 .

[10]  N. Kasagi,et al.  Low-voltage droplet manipulation using liquid dielectrophoresis on electret , 2010 .

[11]  B. L. Henke,et al.  X-Ray Interactions: Photoabsorption, Scattering, Transmission, and Reflection at E = 50-30,000 eV, Z = 1-92 , 1993 .

[12]  C. Leroy,et al.  Principles of Radiation Interaction in Matter and Detection , 2004 .

[13]  J. H. Hubbell,et al.  XCOM : Photon Cross Sections Database , 2005 .

[14]  T. Ohmi,et al.  Neutralization of static electricity by soft X-rays and vacuum UV radiation , 1994 .

[15]  T. Ishikawa,et al.  The Behavior of Ionization Chambers under the Irradiation of High Flux X-Ray Beam , 2022 .

[16]  N. Kasagi,et al.  Seismic Power Generator Using High-Performance Polymer Electret , 2006, 19th IEEE International Conference on Micro Electro Mechanical Systems.

[17]  S. M. Spearing,et al.  Materials issues in microelectromechanical systems (MEMS) , 2000 .

[18]  Yuji Suzuki,et al.  Recent progress in MEMS electret generator for energy harvesting , 2011 .

[19]  Y. Suzuki,et al.  Development of high-performance purfluorinated polymer electret , 2008, 2008 13th International Symposium on Electrets.

[20]  Zhiqiu Lv,et al.  PECVD SiO2/Si3N4 double layers electrets on glass substrate , 2008, IEEE Transactions on Dielectrics and Electrical Insulation.

[21]  B. Fallone,et al.  Production of foil electrets by ionizing radiation in air , 1983 .

[22]  Daigo Miki,et al.  A MEMS electret generator with electrostatic levitation for vibration-driven energy-harvesting applications , 2010 .

[23]  Ulrich Mescheder,et al.  Properties of SiO2 electret films charged by ion implantation for MEMS-based energy harvesting systems , 2009 .

[24]  Wouter Olthuis,et al.  On the charge storage and decay mechanism in silicon dioxide electrets , 1992 .

[25]  Y. Tai,et al.  Micro electret power generator , 2003, The Sixteenth Annual International Conference on Micro Electro Mechanical Systems, 2003. MEMS-03 Kyoto. IEEE.

[26]  Nano-cluster-enhanced High-performance Perfluoro-polymer Electrets for Micro Power Generation , .

[27]  Yoshinori Iguchi,et al.  Soft X-ray Charging Method for a Silicon Electret Condenser Microphone , 2010 .

[28]  B. Ziaie,et al.  A Micromachined Electret-Based Transponder for In Situ Radiation Measurement , 2006, IEEE Electron Device Letters.

[29]  Hiroshi Sameshima,et al.  Power output enhancement of a vibration-driven electret generator for wireless sensor applications , 2011 .

[30]  H. Amjadi.  Charge storage in double layers of thermally grown silicon dioxide and APCVD silicon nitride , 1999 .

[31]  S. Spearing,et al.  Characterization of silicon wafer bonding for power MEMS applications , 2003 .

[32]  Y. Iguchi,et al.  VIBRATION-DRIVEN MEMS ENERGY HARVESTER WITH VERTICAL ELECTRETS , 2010 .

[33]  Jacques Lewiner,et al.  Electrostatic Actuator with Electret , 1995 .