Surface and volume charge transport properties of polyimide revealed by surface potential decay with genetic algorithm

It is very important to understand the surface and volume charge transportation properties of high insulating materials, such as polyimide, in order to find suitable method to mitigate the electrostatic discharge (ESD) of certain sensitive components on spacecraft. An isothermal surface potential decay (ISPD) experiment is performed inside a ground based vacuum chamber on polyimide under a simulated space environment. Immediately after low energy electron beam irradiation on polyimide, the 2D surface potential distributions are measured by a non-contact potential probe under five various temperatures from 298 to 338 K. The surface potential decay of the insulating material can be divided into two categories: transient process and steady state process. The steady state process is determined by the surface and volume charge transportation properties of dielectric. An ISPD model with genetic algorithm (GA) is developed to reveal the steady state surface potential decay experimental results. From the GA analysis, we obtain the surface resistivity, volume Ohmic resistivity, and charge carrier mobility of polyimide at various temperatures. After analyzing the surface and volume charge transportation properties of the material as a function of temperature, we find that the surface resistivity, volume Ohmic resistivity, and charge carrier mobility are well fitted with the Arrhenius law. Consequently, surface activation energy, volume activation energy, and _{trap energy} of polyimide are found as 0.30 eV, 0.32 eV, and 0.54 eV, respectively.