Thermally stimulated discharge current studies of corona polarized pristine and swift heavy ion irradiated kapton-H polyimide

Abstract

Thermally stimulated discharge (tsd) current technique has been used to investigate the corona polarized pristine and swift heavy ion irradiated kapton-H polyimide. The samples of thickness 25 µm were irradiated with 100 MeV Fe + beam (fluence: 1.8 × 10 11 , 2.3 × 10 12 and 1.4 × 10 13 ions/cm 2 ). Corona charged pristine kapton-H samples show two tsd current peaks (P 1 and P 2 ) ∼40-70 and 150-190 • C, respectively. The peak P 1 is in the normal current direction and P 2 is in the abnormal current direction. These peaks are attributed to space charge relaxation process owing to the surface and bulk energy traps, respectively. Thex/d value (x is the mean penetration depth and d is the thickness of the sample) estimated for pristine kapton-H polyimide comes out to be 0.32 and suggests that the space charge distribution is approximated by space charge limited current (SCLC) distribution. However, the SCLC distribution in irradiated sample is not confirmed by largex/d value (0.86). The activation energies estimated from Bucci plot method for peaks P 1 and P 2 vary from 0.66 to 0.97 eV and from 0.92 to 1.31 eV, respectively, depending on the corona voltage. The charge trapping density for surface and bulk traps comes out to be (0.3-10.2) × 10 17 and (4.9-14.6) × 10 17 m −3 , respectively. In the irradiated samples, abnormal tsd currents dominate and there is an enhancement in the bulk charge trapping density (13.2 × 10 18 m −3 ). This enhancement is due to the formation of double/triple bonds and free radicals in irradiated samples. The irradiated corona polarized samples after prolonged aging (10-30 days) show a high temperature maximum with average activation energy of 0.90 eV. This current maximum has been associated with the space charge relaxation process due to bulk deep charge trapping levels.

Thermally stimulated spontaneous current investigations in 75 MeV oxygen-ion-irradiated kapton-H polyimide

“…As the work function of Bi and Al is less than the work function of polyimide sample used, so it make non-ohmic contact with kapton-H polyimide, and the work function of Cr, Cu and Au is more than the work function of sample used in the present investigations that will make ohmic contact with kapton-H polyimide. Figure 2 (Figure 2(a)-(d)) in high fluence-irradiated samples shows a continuous detrapping of charge carriers without giving any current maxima and from this, we are not able to ascertain any particular dielectric relaxation process associated with bulk detrapping centers (6). Spontaneous currents in M 1 -P-M 2 systems lead to polymer electric polarization without application of any external field and occurrence of electrets state in polymer layer.…”

“…Email: sharmaanu81@gmail.com the output will generally be the contribution of different origins (6,7). Hence, a thermally stimulated spontaneous current (TSSC) technique which will provide current from a non-electret polymer deserves a great deal of consideration (8,9).…”

The use of the final thermally stimulated discharge current technique to study the molecular movements around glass transition

“…On the base of TSDC curves obtained for different experimental conditions, at temperatures above room temperature, there were three relaxation peaks distinguished at temperature ranges 343-363 K, 363 -403 K and 403-443 K respectively. These peaks are attributed to space charge relaxation process owing to the surface and bulk energy traps, respectively [15]. Three peaks were observed in thermally stimulated current spectra and they are attributed to the shallow and deep trap levels present in Kapton [18].…”

“…The question about the dominant carrier species responsible for electrical conduction is not correlated with molecular movement. The molecular mobility in PI was investigated by dielectric relaxation spectroscopy [13,14] and by the thermally stimulated discharge current (TSDC) [15,16]. From dielectric measurements it is assumed that the dielectric loss peak at 333 K is mainly governed by the γ-relaxation, the real part ε' of the dielectric permittivity in the temperature range 343-453 K is mainly governed by dipolar and space charge relaxations and in high temperature region (453-513 K) the increase in ε' with temperature is mainly due to interfacial polarization [14].…”

Study of trap structure of thermally polarized polyimide

“…As the polymer surfaces are nonreactive and surface modification involves the generation of high‐energy species such as radicals, ions, and excited electronic state to promote the surface reaction. Surface modification of polymer film is quite often, if it is subjected to high‐energy species such as flame, plasma, UV, laser, X‐ray and γ‐ray, electron beam, ion beam, high electric field, and temperature 1–3. Therefore, the study of surface traps/defects is essential to understand complete electrical morphology of polymer through suitable technique.…”