Effect of Ar + Ion Implantation on Electrical Conductivity of Polycarbonate P. K. Goyal, V. Kumar, Renu Gupta, S. Kumar, P. Kumar, and D. Kanjilal Citation: AIP Conference Proceedings 1349, 543 (2011); doi: 10.1063/1.3605973 View online: http://dx.doi.org/10.1063/1.3605973 View Table of Contents: http://scitation.aip.org/content/aip/proceeding/aipcp/1349?ver=pdfcov Published by the AIP Publishing Articles you may be interested in Electrical conduction in 100 keV Kr+ ion implanted poly (ethylene terephthalate) AIP Conf. Proc. 1447, 595 (2012); 10.1063/1.4710144 Study of Electrical Conductivity of Kr + Ion implanted Polycarbonate in Relation to Carbon Structure AIP Conf. Proc. 1393, 147 (2011); 10.1063/1.3653652 Effect of dc electric field on conductivity and giant permittivity of K x Ti y Ni 1 − x − y O Appl. Phys. Lett. 90, 242913 (2007); 10.1063/1.2743929 Surface electrical conductivity in ultrathin single-wall carbon nanotube/polymer nanocomposite films Appl. Phys. Lett. 88, 164101 (2006); 10.1063/1.2193812 Dielectrophoresis of nanoscale double-stranded DNA and humidity effects on its electrical conductivity Appl. Phys. Lett. 87, 183102 (2005); 10.1063/1.2117626
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Effect of Ar+ Ion Implantation on Electrical Conductivity of Polycarbonate P. K. Goyala*, V. Kumara, Renu Guptaa, S. Kumara, P. Kumarb and D. Kanjilalb a
b
Department of Physics, Kurukshetra University, Kurukshetra-136 119, India Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi-110 067, India * E-mail:
[email protected]
Abstract. The samples of Polycarbonate (PC) have been implanted to 100 keV Ar+ ions at the fluences 5x1015- 2x1016 cm-2. It has been observed that the surface conductivity of these implanted samples enhances with increasing implantation dose. Such an increase in the conductivity may be as a result of the formation of conjugated double bonds and carbonization of the implanted layer. Keywords: Ion-Implantation, Surface Conductivity, Polycarbonate. PACS: 81.05.Lg, 81.15.Lm, 81.40.Rs.
INTRODUCTION Due to good spatial localization of the implanted atoms and fine control on the implantation dose, the ion implantation technique is often used for the modification of surface properties of the materials as per specific requirements. As a result of the ion implantation in polymers, the polymer structure and properties change considerably due to two major processes involved i.e. chain scissioning and crosslinking [1-2]. The various effects such as ionization, displacing of atoms, sputtering, carbonization, production of free radicals etc. [2-4] are responsible for the modification of various electrical, optical and dielectric properties of polymers. In this work, polycarbonate samples were implanted to 100 keV Ar+ ions up to the fluence of 2x1016 cm-2 and their surface conductivity and chemical structure were studied by different techniques.
New Delhi, India. The residual pressure in the implanter target chamber was about 10-6 torr. The ion current density was kept below 500 nA/cm2 to prevent the thermal degradation of the samples. The electrical conductivity measurements, at room temperature, were then carried out with two point probe method using Keithley 5110 Digital Electrometer, interfaced with computer. The Raman spectra of the virgin and ion implanted polycarbonate samples were analysed to determine the changes in chemical composition of this polymer as a result of implantation.
RESULTS AND DISCUSSION The voltage and current values for virgin and Ar+ implanted PC samples in the voltage range 0-100V were recorded at room temperature. The V-I characteristics of virgin and implanted samples are shown in Figure 1. The electrical conductivity of the implanted surface has been determined using the relation [5]
EXPERIMENTAL The bulk sheet of polycarbonate (monomer composition C16H14O3) of thickness 250 micron procured from Goodfellow, United Kingdom was cut into samples of area 15x15 mm2. These samples were irradiated to 100 keV Ar+ ions at the doses 5x1015, 1x1016 and 2x1016 ions/cm2 at room temperature using Low Energy Ion Beam Facility (LEIBF) at IUAC,
σs =
cosh −1 (d 2r0 ) πR
where, σs = surface conductivity, d = separation between electrodes, r0 = radius of the circular electrode and R = resistance measured on the conductive surface.
Solid State Physics, Proceedings of the 55th DAE Solid State Physics Symposium 2010 AIP Conf. Proc. 1349, 543-544 (2011); doi: 10.1063/1.3605973 © 2011 American Institute of Physics 978-0-7354-0905-7/$30.00
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TABLE 1. Electrical Conductivity of Virgin and Ar+ Ion Implanted Polycarbonate.
1.2E-07 virgin 5x10^15 1.0E-07
1x10^16 2x10^16
Sr. No.
Current (A)
8.0E-08
6.0E-08
4.0E-08
2.0E-08
Ion Dose (ion/cm2)
Surface Conductivity (S)
1
virgin
3.64E-14
2
5x1015
3.04E-11
3
1x1016
2.62E-10
4
16
7.70E-10
2x10
0.0E+00 5
25
45
65
85
105
Voltage (V)
FIGURE 1. V-I Characteristics of virgin and ion implanted polycarbonate.
The measured values of surface conductivity at different implantation doses have been listed in Table 1. From this table, it is clear that the value of electrical conductivity increases from ~10-14 S for virgin PC sample to ~10-9 S for the sample implanted to the dose 2x1016 ions/cm2. Such an increase in the conductivity may be explained on the basis of the fact that ion implantation in polymers, leads to the formation of free radicals & dangling bonds, release of low molecular weight volatile species like hydrogen, trapping of high molecular weight fragments, etc leading to the creation of carbonaceous clusters on the implanted surface which are rich in charge carriers [6-7] which provide the continuous path for the charge transfer within the insulating polymer chain. The creation of such carbonaceous clusters on the implanted surface has been confirmed through Raman spectroscopy (Figure 2) which revealed that all characteristic peaks of virgin PC have disappeared with the appearance of a band at wavenumber ~1530 cm-1 corresponding to the characteristic G-bands of hydrogenated amorphous carbon [6-7].
CONCLUSION The surface conductivity of 100 keV Ar+ implanted PC has been found to increase up to 5 orders of magnitudes at the implantation dose of 2x1016 ions/cm2. The formation of a three dimensional carbonaceous network consisting of disordered bonds emerges in the implanted regions of the polycarbonate as confirmed through Raman analysis is considered responsible for increased surface conductivity in implanted samples.
ACKNOWLEDGEMENTS Two of the authors (P. K. Goyal & V. Kumar) are thankful to Council of Scientific & Industrial Research (CSIR) New Delhi, India for financial assistance in form of Senior Research Fellowship (SRF).
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FIGURE 2. Raman spectra of Virgin and Implanted polycarbonate.
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