Thermal Currents from Corona Charged Mylar

Abstract

Thermal currents have been obtained from corona-charged Mylar. The results are interpreted in terms of electron and/or ion trapping and subsequent release upon reheating. A theory is developed for thermal release of these ``near surface'' charged specimens when no external field is applied. A new method is presented to obtain energies for a series of peaks present in complex thermal current spectra. The trapping parameters are also determined using both the initial rise analysis of Garlick and Gibson, and the curve fitting technique of Cowell and Woods. The results are consistent with four discrete traps in Mylar at depths of 0.55, 0.85, 1.4 and 2.2 (all ±0.1) eV. The 0.55- and 0.85-eV traps are electronic, that at 1.4 eV is either an electronic trap with a Coulomb barrier, or ionic. The 2.2-eV trap is either ionic, interfacial, or involves dissociation of a complex with subsequent release of an electron to the conduction band. Assuming that the traps empty under monomolecular conditions, analysis of the thermal-current peaks yields trap densities of the order of 1016/cm3, an electron mobility—lifetime product of about 10−10 cm2/V, and escape probabilities that agree with those determined from isothermal charge decay.