Neutralization theory of static surface charges by an ionizer under wide gas pressure environments

The neutralization of static charges by an ionizer under wide gas pressure environments has been investigated theoretically, where the time required for the surface charge neutralization and the value of charge in-balance were predicted in terms of Knudsen numbers (Kn: mean free path of ion/characteristics length). The results show that: (1) the steady-state potential due to the charge in-balance (residual potential) increases with decreasing Kn and increases with increasing diffusion current ratio) for the positive- and negative-ion-generating gas environments (electronegative gas such as air, oxygen, etching gases, etc.); (2) the steady-state imbalance potential decreases with increasing Kn for electron-positive ion-generating gas such as nitrogen, noble gas, etc.; and (3) the charge neutralization time is much faster for electron-positive-ion-generating gas than that of the negative-positive-ion-generating environments under wide gas pressure conditions.