Charge dynamics in electron-irradiated polymers

Abstract

Recent studies of charge trapping and charge transport in polymer lms irradiated and charged with monoenergetic electrons of range smaller than the sample thickness and thereafter stored or annealed under various conditions are discussed. An analytical model used to describe the phenomena takes the following parameters into consideration: Charge and energy deposition pro les, charge drift due to a shallow-trap-modulated mobility, deep trapping without release, trap lling due to a nite trap density, and ohmic relaxation due to a radiation-induced conductivity during irradiation and its delayed component after irradiation. The model calculations show the e ect of various parameters on the shape of the initial charge distribution and on its evolution with annealing time. -Experiments with the laser-induced pressure-pulse LIPP method on 12 and 25 m thick uorocarbon and polyimide lms, charged with 10 or 20 keV electron beams, respectively, yield the charge distributions after irradiation and the changes of the distributions due to annealing of the samples at 120 C for various times. A comparison of experimental and analytical results reveals the trapping kinetics and permits to estimate the deep-trap density and the -product, where is the trap-modulated mobility and is the trapping time.

Experimental characterisation of charge distribution and transport in electron irradiated PMMA

“…There is now a considerable amount of literature concerned with experimental characterization of space charge [6][7][8][9] and with phenomenological models of space charge formation and discharge [10]. However space charge accumulation and discharge together with related trapping-detrapping phenomena are still relevant.…”

Investigation Into Surface Potential Decay of Polyimide by Unipolar Charge Transport Model

“…It was found that the carrier mobility of polyimide was in the range 2.06 × 10 −17 -3 × 10 −15 m 2 ·V −1 ·s −1 . In addition, Sessler et al [29], [30], [44] suggested that μ/P tr could be assumed as a constant, and μ/P tr was in the range from 3 × 10 −15 to 6 × 10 −13 m 2 ·V −1 for polyimide. According to [46], we set μ ≈ 3.15 × 10 −16 m 2 ·V −1 ·s −1 and μ/P tr ≈ 2.27 × 10 −13 m 2 ·V −1 in the following simulations.…”

“…Deep trapped charges can be thermally released to the shallow traps with a detrapping probability [25]. These charge transport processes of insulators are proved by experimental results by using space charge mapping techniques, such as pulsed electroacoustic (PEA) [26]- [28], laserinduced pressure pulse (LIPP) [29], [30], and pressure wave propagation [31]. Fig.…”

Study of degradation by heat and heat‐resistance property in electret condenser microphone

“…Figure 3 shows the numerically calculated variation of the surface potential from b = 0 µm to 12 µm. For the FEP 12.5 µm actually used for a fixed-electrode electret, the initial charge distribution is near 2 µm according to the data of Sessler and Yang [6]. At b = 2 µm, a potential of -165 V appears on the surface of the FEP.…”