THE TRAPPING AND DISTRIBUTION OF CHARGE IN POLARIZED POLYMETHYLMETHACRYLATE UNDER ELECTRON-BEAM IRRADIATION

A scanning electron microscope (SEM) mirror-image method (MIM) is empl oyed to investigate the charging behaviour of polarized polymethylmeth acrylate (PMMA) under electron-beam irradiation. An ellipsoid is used to model the trapped charge distribution and a fitting method is emplo yed to calculate the total amount of the trapped charge and its distri bution parameters. The experimental results reveal that the charging a bility decreases with increasing applied electric field, which polariz es the PMMA sample, whereas the trapped charge distribution is elongat ed along the direction of the applied electric field and increases wit h increasing applied electric field. The charges are believed to be tr apped in some localization states, of activation energy and radius est imated to be about 19.6 meV and 4.6 x 10(-8) m, respectively.