NOVEL THROUGH-SUBSTRATE CHARGING METHOD FOR ELECTRET GENERATOR USING SOFT X-RAY IRRADIATION

A new charging method with soft X-ray irradiation has been investigated for MEMS electret generator. Since the radiation can penetrate through Si/glass substrate and generate ions inside air gap, electret can be charged even after assembling/packaging process. As proof of the concept, a CYTOP film was charged through the Al foil electrode using soft X-ray irradiation. We found that charging properties such as uniformity, stability and controllability are as good as those of electrets charged by conventional corona discharge. Although the charging time in air is longer than that for corona discharge, reduction of the charging time is possible by using higher-energy X-ray and other gases species with higher absorption factor to soft X-ray.