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Annealing of PEEK, PET and PI implanted with Co ions at high fluencies
Nuclear Instruments and Methods in Physics Research B 307 (2013) 598–602
Contents lists available at SciVerse ScienceDirect
Nuclear Instruments and Methods in Physics Research B journal homepage: www.elsevier.com/locate/nimb
Annealing of PEEK, PET and PI implanted with Co ions at high fluencies A. Mackova a,b,⇑, P. Malinsky a,b, R. Miksova a,b, H. Pupikova a,b, R.I. Khaibullin c, V.F. Valeev c, V. Svorcik d, P. Slepicka d a
Nuclear Physics Institute of the Academy of Sciences of the Czech Republic v.v.i., 250 68 Rez, Czech Republic Department of Physics, Faculty of Science, J.E. Purkinje University, Ceske mladeze 8, 400 96 Usti nad Labem, Czech Republic c Radiation Physics Laboratory, Kazan Physical-Technical Institute, Sibirsky Trakt 10/7, 420029 Kazan, Russia d Department of Solid State Engineering, Institute of Chemical Technology, 166 28 Prague, Czech Republic b
a r t i c l e
i n f o
Article history: Received 25 September 2012 Received in revised form 13 November 2012 Accepted 19 November 2012 Available online 21 January 2013 Keywords: Co-ion implantation Polymers Depth profiles RBS TEM AFM
a b s t r a c t The properties of implanted polymers strongly depend on the implantation ion fluence and on the properties of the implanted atoms. The stability of synthesized nano-structures during further technological steps like annealing is of importance for their possible applications. Polyimide (PI), polyetheretherketone (PEEK), and polyethyleneterephtalate (PET) were implanted with 40 keV Co+ ions at room temperature at fluences ranging from 0.2 1016 cm 2 to 1.0 1017 cm–2 and annealed at a temperature of 200 °C. The implanted depth profiles of as-implanted and annealed samples, determined by the RBS method, were compared with the results of SRIM 2012 simulations. The structural and compositional changes of the implanted and subsequently annealed polymers were characterized by RBS and UV–vis spectroscopy. The surface morphology of as-implanted and annealed samples was examined by the AFM method and their electrical properties by sheet resistance measurement. Ó 2013 Elsevier B.V. All rights reserved.
1. Introduction Metal/polymer nanostructured materials are of high importance for plastic electronics [1,2]. Metal ion implantation on polymers at ion energies below 100 keV to very high fluences leads to the formation of metal-rich, carbonized surface layers with interesting physico-chemical properties. Ion implantation at high fluencies is also accompanied by several interesting phenomena such as metal-atom nucleation into nanoparticles with specific electromagnetic and optical properties. The properties of metal-implanted polymers can further be affected by annealing. The properties of three different synthetic polymers implanted with 40 keV Co+ ions to high fluences and annealed at a temperature of 200 °C have been studied by various methods with the aim of obtaining more complete information on the processes induced by ion implantation and annealing and on their effect on the properties of the nanostructures formed on different polymers. 2. Experimental PI, PEEK and PET 50-lm thick foils supplied by Goodfellow Ltd., were implanted with 40 keV Co+ ions to the fluencies ranging from ⇑ Corresponding author at: Nuclear Physics Institute of the Academy of Sciences of the Czech Republic v.v.i., 250 68 Rez, Czech Republic. Tel.: +420 266 172 102. E-mail address: [email protected] (A. Mackova). 0168-583X/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.nimb.2012.11.078
0.2 1016 to 1.0 1017 cm–2 on the ILU-3 accelerator designed in the Kazan Physical-Technical Institute, Russia. The implantation was performed at RT and at an ion current density of 4 lA cm 2. The implanted samples were subjected to annealing at a temperature of 200 °C, which is below or above the glassy transition temperature Tg of polymers under study (for PET, PEEK and PI, the glassy transition temperatures are 98 °C, 145 °C and 250 °C, respectively). This temperature had been chosen to facilitate comparison with our previous experiments on implanted polymers [3]. The depth profiles of the implanted Co atoms and the composition of the implanted layers were determined by Rutherford BackScattering spectrometry (RBS). RBS spectra were measured using a beam of 2.0 MeV He+ ions. The primary beam comes at an angle of 0° with respect to the sample surface normal. An Ultra-Ortec PIPS detector recorded He+ ions scattered at a laboratory scattering angle of 170°. The typical beam current was 20 nA. To reduce the effects of sample degradation during the RBS analysis, several particular spectra were measured on different beam spots and the final spectrum was obtained by summing the individual spectra. The RBS spectra were evaluated by means of the GISA [4] code using cross-section data from IBANDL [5]. The surface morphology of the implanted polymers was characterized by Atomic Force Microscopy (AFM) using Digital Instruments CP II Veeco in tapping mode with a silicon tip (a spring constant of 20–80 N/m). The arithmetic average height parameter (Ra) is defined as the average absolute deviation of the roughness
A. Mackova et al. / Nuclear Instruments and Methods in Physics Research B 307 (2013) 598–602
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Fig. 1. The Co concentration profiles determined by RBS for implantation fluences of 0.2 1016 cm 2 and 1.0 1016 cm–2 in (a) PEEK, (b) PET after the annealing procedure at a temperature of 200 °C. The SRIM-simulated profile is shown by the solid line. The Co depth profiles in PI are analogous to PEEK.
irregularities from the mean line over one sampling length [6]. The sheet resistance of the as-implanted and annealed samples was measured using the standard two-point technique with Keithley 487 picoampermeter under a pressure of 103 Pa and in the voltage interval 0–150 V. The UV–vis measurement in a wavelength range of 150–800 nm was performed using a Perkin–Elmer device [7]. 3. Results and discussion The depth profiles of the implanted Co atoms in as-implanted PET and PEEK (ion fluencies of 0.2 1016 and 1.0 1016 cm 2)
and the same polymers annealed at 200 °C for 20 min, determined by RBS, are shown in Fig. 1. The measured depth profiles are compared to those simulated by the SRIM 2012 code [8]. The discrepancies between the measured and simulated profiles are obvious. The measured depth profiles in the as-implanted samples are much broader than the simulated ones. For all three polymers, the values of the range straggling DRP of the measured profiles are about twice as high as the simulated ones, whereas the PEEK and PI depth profiles are similar. Rather slight differences between the measured and simulated projected ranges RP are also observed. The annealing of the samples implanted to the fluencies below 1.0 1016 cm 2 does slightly influence the
Fig. 2. The concentration depth profiles of oxygen, determined from the RBS spectra, in (a) PET, (b) PI and (c) PEEK, implanted with 40 keV Co ions at a fluence ranging from 0.2 1016 cm 2 to 1.0 1017 cm 2 and annealed at 200 °C for 20 min.
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A. Mackova et al. / Nuclear Instruments and Methods in Physics Research B 307 (2013) 598–602
Fig. 3. The AFM images of PI and PET implanted with 40 keV Co+ ions: (a) PI as-implanted at a fluence of 0.2 1016 cm 2, (b) PI implanted at a fluence of 0.2 1016 cm 2 and annealed at 200 °C for 20 min, (c) PI implanted at a fluence of 1.0 1017 cm 2 and annealed, (d) PET as-implanted at a fluence of 0.2 1016 cm 2, (e) PET implanted at a fluence of 0.2 1016 cm 2 and annealed, and (f) PET implanted at a fluence of 1.0 1016 cm 2 and annealed.
shape of the depth profiles and the position of the concentration maximum. The most pronounced change in the position and shape of the Co depth profile is observed after the annealing of the PET implanted at a fluence above 1.0 1016 cm 2. Similar
phenomena are observed at the PET implanted and annealed by different ion species see also [3,9]. The shift of the maximum Co concentration after annealing may be related to the thermal diffusion of Co particles.
Fig. 4. The UV–vis spectra of as-implanted (a), (c) and annealed (b), (d) polymers, PI and PET, implanted with 40 keV Co+ ions, at fluencies below 1 1017 cm at 200 °C.
2
and annealed
A. Mackova et al. / Nuclear Instruments and Methods in Physics Research B 307 (2013) 598–602
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Fig. 5. The electric resistance of as-implanted and annealed (a) PET, (b) PI and (c) PEEK.
The depletion of light elements caused by heavy ion irradiation leads to a gradual carbonisation of the irradiated polymers. This well-known effect has been observed elsewhere [10,11]. The subsequent annealing can cause a structural reconstruction of the polymer. The polymer implanted to high fluencies exhibits a significant enrichment in carbonized structures with conjugated bonds and a minority of radicals in the implanted layer. The carbonized layer represents a diffusion barrier for an oxygen from the ambient atmosphere as was shown in [12]. The oxygen depth profiles in the implanted surface layer, determined from the RBS spectra on the as-implanted sample, subsequently annealed at 200 °C, are shown in Fig. 2. An oxygen depletion to 30% of the virgin oxygen concentration in PEEK and 50% in PI was observed after the implantation to ion fluences of 1.0 1017 cm 2. A negligible oxygen depletion was noticed in the as-implanted PET. However, the annealing of PET and PI, implanted to a fluence of 1.0 1017 cm 2, results in an oxygen depletion to 15% and 50% of its initial concentration in PI and PET, respectively (see Fig. 2b and a). On the other hand, the annealing leads to slight oxygen enrichment in the ion implanted surface layer of PEEK (Fig. 2c). Typical AFM images of PI and PET implanted at fluencies below 1.0 1017 cm 2 and annealed at 200 °C for 20 min are shown in Fig. 3. It is evident that the annealing of the samples implanted to a fluence of 0.2 1016 cm 2 leads to slight changes in the sur-
face morphology, manifested by an increase of the surface roughness Ra. The increase in Ra is greater for the samples implanted at a fluence above 1.0 1016 cm 2 and annealed at 200 °C. There is a large difference between the morphology of annealed PET and PI samples implanted at different ion fluencies, a ‘spiky’ structure on the implanted and annealed PET sample (see Fig. 3d–f) is replaced by a ‘bulge’ structure on the PI sample under the same preparation conditions (see Fig. 3a–c). The implanted and annealed PEEK samples do not show dramatic changes in the surface morphology after the annealing procedure. UV–vis spectroscopy is used for the characterisation of the structural changes after the ion implantation. The typical UV– vis spectra from the implanted PI and PET samples are shown in Fig. 4a, c. Ion irradiation creates compact carbonaceous clusters, which may also be responsible for enhanced electrical conductivity, a narrower optical band gap and higher optical absorbance [13]. The absorbance increases dramatically even for the lowest ion fluence of 0.2 1016 cm 2. With increasing ion fluence, the absorbance increases gradually in the case of PET (see Fig. 4c). In PEEK and PI, the saturation of absorbance is observed for an implantation fluence of about 1.0 1017 cm 2. This finding is in agreement with our previous experiments performed with different ion species [14]. The UV–vis absorbance of as-implanted PI is very little influenced by the sample annealing (see Fig. 4a and b). In PEEK and PET, the annealing at 200 °C results
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in an absorbance increase for all the implanted fluencies (see Fig. 4c and d). The measurement of the electrical resistance in as-implanted and annealed polymers is presented in Fig. 5a–c for PET, PI and PEEK, respectively. The resistance is a decreasing function of the ion fluence. The observed resistance evolution is comparable with that reported in [14,15]. After the annealing, the resistance further decreases in the case of PET and PEEK for implantation fluencies above 5 1016 cm 2 (see Fig. 5a). In PI, however, annealing does not change the electrical resistance significantly (see Fig. 5b).
investigations, the ion implantation, accompanied by polymer carbonisation, leads to a rapid decrease of electrical sheet resistance, which could be further decreased by annealing. Acknowledgements The research has been realised at the CANAM (Center of Accelerators and Nuclear Analytical Methods) infrastructure and has been supported by project No. P108/12/G108 and LM 2011019. References
4. Conclusions The structural and compositional changes of PET, PI and PEEK implanted by 40 keV Co+ ions and annealed at 200 °C for 20 min were studied using RBS and UV–vis spectroscopy. The measured as-implanted Co profiles differ from those simulated by the SRIM code, which does not take into account the gradual degradation of the polymer matrix during the implantation process. For all the polymers, the measured profile width is about twice as high as the simulated one. The annealing of the samples implanted at fluencies below 1.0 1016 cm 2 slightly influences the shape of the depth profiles and the position of the concentration maximum. The most pronounced profile change is observed on PET. It may be concluded that the annealing under the present conditions does not enhance the mobility of the implanted Co atoms much in PEEK and PI below an implantation fluence of 1.0 1016 cm 2. Specific changes in the polymer surface morphology are observed on AFM images, with the most significant ones occurring on PI implanted to different ion fluencies. The annealing causes an enhancement of the UV–vis absorbance of PEEK and PET implanted polymers, which could be connected to the structural changes followed by a decrease of electrical sheet resistance. In accordance with earlier
[1] A.L. Stepanov, R.I. Khaibullin, Rev. Adv. Mater. Sci. 7 (2004) 108–125. [2] F.S. Teixeira, M.C. Salvadori, M. Cattani, I.G. Brown, J. Appl. Phys. 105 (2009) 064313. [3] P. Malinsky, A. Mackova, V. Hnatowicz, R.I. Khaibullin, V.F. Valeev, P. Slepicka, V. Svorcik, M. Slouf, V. Perina, Nucl. Instr. Meth. Phys. Res. B 272 (2012) 396– 399. [4] J. Saarilahti, E. Rauhala, Nucl. Instr. Meth. Phys. Res. B64 (1992) 734. [5] IBANDL,. [9] A. Mackova, P. Malinsky, R. Miksova, R.I. Khaibullin, V.F. Valeev, V. Svorcik, P. Slepicka, M. Slouf, Appl. Surf. Sci. (2010), http://dx.doi.org/10.1016/ j.apsusc.2012.12.071. [10] D. Fink (Ed.), Fundamentals of Ion-Irradiated Polymers, Springer, Berlin, Heidelberg, 2004. [11] V. Hnatowicz, J. Vacik, J. Cervena, V. Perina, V. Svorcik, Rybka, Nucl. Instr. Meth. Phys. Res. B 136–138 (1998) 568. [12] V. Popok, Rev. Adv. Mater. Sci. 30 (2012) 1–26. [13] J. Tauc, R. Grigorovici, A. Bavcu, Phys. Status Solidi 15 (1996) 627. [14] A. Mackova, J. Bocan, R.I. Khaibullin, V.F. Valeev, P. Slepicka, P. Sajdl, V. Švorcˇík, Nucl. Instr. Meth. Phys. Res. B 267 (2009) 1549–1552. [15] W. Yuguang, Z. Tonghe, Z. Huixing, Z. Xiaoji, D. Zhiwei, Surf. Coat. Technol. 131 (2000) 520.
Contents lists available at SciVerse ScienceDirect
Nuclear Instruments and Methods in Physics Research B journal homepage: www.elsevier.com/locate/nimb
Annealing of PEEK, PET and PI implanted with Co ions at high fluencies A. Mackova a,b,⇑, P. Malinsky a,b, R. Miksova a,b, H. Pupikova a,b, R.I. Khaibullin c, V.F. Valeev c, V. Svorcik d, P. Slepicka d a
Nuclear Physics Institute of the Academy of Sciences of the Czech Republic v.v.i., 250 68 Rez, Czech Republic Department of Physics, Faculty of Science, J.E. Purkinje University, Ceske mladeze 8, 400 96 Usti nad Labem, Czech Republic c Radiation Physics Laboratory, Kazan Physical-Technical Institute, Sibirsky Trakt 10/7, 420029 Kazan, Russia d Department of Solid State Engineering, Institute of Chemical Technology, 166 28 Prague, Czech Republic b
a r t i c l e
i n f o
Article history: Received 25 September 2012 Received in revised form 13 November 2012 Accepted 19 November 2012 Available online 21 January 2013 Keywords: Co-ion implantation Polymers Depth profiles RBS TEM AFM
a b s t r a c t The properties of implanted polymers strongly depend on the implantation ion fluence and on the properties of the implanted atoms. The stability of synthesized nano-structures during further technological steps like annealing is of importance for their possible applications. Polyimide (PI), polyetheretherketone (PEEK), and polyethyleneterephtalate (PET) were implanted with 40 keV Co+ ions at room temperature at fluences ranging from 0.2 1016 cm 2 to 1.0 1017 cm–2 and annealed at a temperature of 200 °C. The implanted depth profiles of as-implanted and annealed samples, determined by the RBS method, were compared with the results of SRIM 2012 simulations. The structural and compositional changes of the implanted and subsequently annealed polymers were characterized by RBS and UV–vis spectroscopy. The surface morphology of as-implanted and annealed samples was examined by the AFM method and their electrical properties by sheet resistance measurement. Ó 2013 Elsevier B.V. All rights reserved.
1. Introduction Metal/polymer nanostructured materials are of high importance for plastic electronics [1,2]. Metal ion implantation on polymers at ion energies below 100 keV to very high fluences leads to the formation of metal-rich, carbonized surface layers with interesting physico-chemical properties. Ion implantation at high fluencies is also accompanied by several interesting phenomena such as metal-atom nucleation into nanoparticles with specific electromagnetic and optical properties. The properties of metal-implanted polymers can further be affected by annealing. The properties of three different synthetic polymers implanted with 40 keV Co+ ions to high fluences and annealed at a temperature of 200 °C have been studied by various methods with the aim of obtaining more complete information on the processes induced by ion implantation and annealing and on their effect on the properties of the nanostructures formed on different polymers. 2. Experimental PI, PEEK and PET 50-lm thick foils supplied by Goodfellow Ltd., were implanted with 40 keV Co+ ions to the fluencies ranging from ⇑ Corresponding author at: Nuclear Physics Institute of the Academy of Sciences of the Czech Republic v.v.i., 250 68 Rez, Czech Republic. Tel.: +420 266 172 102. E-mail address: [email protected] (A. Mackova). 0168-583X/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.nimb.2012.11.078
0.2 1016 to 1.0 1017 cm–2 on the ILU-3 accelerator designed in the Kazan Physical-Technical Institute, Russia. The implantation was performed at RT and at an ion current density of 4 lA cm 2. The implanted samples were subjected to annealing at a temperature of 200 °C, which is below or above the glassy transition temperature Tg of polymers under study (for PET, PEEK and PI, the glassy transition temperatures are 98 °C, 145 °C and 250 °C, respectively). This temperature had been chosen to facilitate comparison with our previous experiments on implanted polymers [3]. The depth profiles of the implanted Co atoms and the composition of the implanted layers were determined by Rutherford BackScattering spectrometry (RBS). RBS spectra were measured using a beam of 2.0 MeV He+ ions. The primary beam comes at an angle of 0° with respect to the sample surface normal. An Ultra-Ortec PIPS detector recorded He+ ions scattered at a laboratory scattering angle of 170°. The typical beam current was 20 nA. To reduce the effects of sample degradation during the RBS analysis, several particular spectra were measured on different beam spots and the final spectrum was obtained by summing the individual spectra. The RBS spectra were evaluated by means of the GISA [4] code using cross-section data from IBANDL [5]. The surface morphology of the implanted polymers was characterized by Atomic Force Microscopy (AFM) using Digital Instruments CP II Veeco in tapping mode with a silicon tip (a spring constant of 20–80 N/m). The arithmetic average height parameter (Ra) is defined as the average absolute deviation of the roughness
A. Mackova et al. / Nuclear Instruments and Methods in Physics Research B 307 (2013) 598–602
599
Fig. 1. The Co concentration profiles determined by RBS for implantation fluences of 0.2 1016 cm 2 and 1.0 1016 cm–2 in (a) PEEK, (b) PET after the annealing procedure at a temperature of 200 °C. The SRIM-simulated profile is shown by the solid line. The Co depth profiles in PI are analogous to PEEK.
irregularities from the mean line over one sampling length [6]. The sheet resistance of the as-implanted and annealed samples was measured using the standard two-point technique with Keithley 487 picoampermeter under a pressure of 103 Pa and in the voltage interval 0–150 V. The UV–vis measurement in a wavelength range of 150–800 nm was performed using a Perkin–Elmer device [7]. 3. Results and discussion The depth profiles of the implanted Co atoms in as-implanted PET and PEEK (ion fluencies of 0.2 1016 and 1.0 1016 cm 2)
and the same polymers annealed at 200 °C for 20 min, determined by RBS, are shown in Fig. 1. The measured depth profiles are compared to those simulated by the SRIM 2012 code [8]. The discrepancies between the measured and simulated profiles are obvious. The measured depth profiles in the as-implanted samples are much broader than the simulated ones. For all three polymers, the values of the range straggling DRP of the measured profiles are about twice as high as the simulated ones, whereas the PEEK and PI depth profiles are similar. Rather slight differences between the measured and simulated projected ranges RP are also observed. The annealing of the samples implanted to the fluencies below 1.0 1016 cm 2 does slightly influence the
Fig. 2. The concentration depth profiles of oxygen, determined from the RBS spectra, in (a) PET, (b) PI and (c) PEEK, implanted with 40 keV Co ions at a fluence ranging from 0.2 1016 cm 2 to 1.0 1017 cm 2 and annealed at 200 °C for 20 min.
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A. Mackova et al. / Nuclear Instruments and Methods in Physics Research B 307 (2013) 598–602
Fig. 3. The AFM images of PI and PET implanted with 40 keV Co+ ions: (a) PI as-implanted at a fluence of 0.2 1016 cm 2, (b) PI implanted at a fluence of 0.2 1016 cm 2 and annealed at 200 °C for 20 min, (c) PI implanted at a fluence of 1.0 1017 cm 2 and annealed, (d) PET as-implanted at a fluence of 0.2 1016 cm 2, (e) PET implanted at a fluence of 0.2 1016 cm 2 and annealed, and (f) PET implanted at a fluence of 1.0 1016 cm 2 and annealed.
shape of the depth profiles and the position of the concentration maximum. The most pronounced change in the position and shape of the Co depth profile is observed after the annealing of the PET implanted at a fluence above 1.0 1016 cm 2. Similar
phenomena are observed at the PET implanted and annealed by different ion species see also [3,9]. The shift of the maximum Co concentration after annealing may be related to the thermal diffusion of Co particles.
Fig. 4. The UV–vis spectra of as-implanted (a), (c) and annealed (b), (d) polymers, PI and PET, implanted with 40 keV Co+ ions, at fluencies below 1 1017 cm at 200 °C.
2
and annealed
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Fig. 5. The electric resistance of as-implanted and annealed (a) PET, (b) PI and (c) PEEK.
The depletion of light elements caused by heavy ion irradiation leads to a gradual carbonisation of the irradiated polymers. This well-known effect has been observed elsewhere [10,11]. The subsequent annealing can cause a structural reconstruction of the polymer. The polymer implanted to high fluencies exhibits a significant enrichment in carbonized structures with conjugated bonds and a minority of radicals in the implanted layer. The carbonized layer represents a diffusion barrier for an oxygen from the ambient atmosphere as was shown in [12]. The oxygen depth profiles in the implanted surface layer, determined from the RBS spectra on the as-implanted sample, subsequently annealed at 200 °C, are shown in Fig. 2. An oxygen depletion to 30% of the virgin oxygen concentration in PEEK and 50% in PI was observed after the implantation to ion fluences of 1.0 1017 cm 2. A negligible oxygen depletion was noticed in the as-implanted PET. However, the annealing of PET and PI, implanted to a fluence of 1.0 1017 cm 2, results in an oxygen depletion to 15% and 50% of its initial concentration in PI and PET, respectively (see Fig. 2b and a). On the other hand, the annealing leads to slight oxygen enrichment in the ion implanted surface layer of PEEK (Fig. 2c). Typical AFM images of PI and PET implanted at fluencies below 1.0 1017 cm 2 and annealed at 200 °C for 20 min are shown in Fig. 3. It is evident that the annealing of the samples implanted to a fluence of 0.2 1016 cm 2 leads to slight changes in the sur-
face morphology, manifested by an increase of the surface roughness Ra. The increase in Ra is greater for the samples implanted at a fluence above 1.0 1016 cm 2 and annealed at 200 °C. There is a large difference between the morphology of annealed PET and PI samples implanted at different ion fluencies, a ‘spiky’ structure on the implanted and annealed PET sample (see Fig. 3d–f) is replaced by a ‘bulge’ structure on the PI sample under the same preparation conditions (see Fig. 3a–c). The implanted and annealed PEEK samples do not show dramatic changes in the surface morphology after the annealing procedure. UV–vis spectroscopy is used for the characterisation of the structural changes after the ion implantation. The typical UV– vis spectra from the implanted PI and PET samples are shown in Fig. 4a, c. Ion irradiation creates compact carbonaceous clusters, which may also be responsible for enhanced electrical conductivity, a narrower optical band gap and higher optical absorbance [13]. The absorbance increases dramatically even for the lowest ion fluence of 0.2 1016 cm 2. With increasing ion fluence, the absorbance increases gradually in the case of PET (see Fig. 4c). In PEEK and PI, the saturation of absorbance is observed for an implantation fluence of about 1.0 1017 cm 2. This finding is in agreement with our previous experiments performed with different ion species [14]. The UV–vis absorbance of as-implanted PI is very little influenced by the sample annealing (see Fig. 4a and b). In PEEK and PET, the annealing at 200 °C results
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A. Mackova et al. / Nuclear Instruments and Methods in Physics Research B 307 (2013) 598–602
in an absorbance increase for all the implanted fluencies (see Fig. 4c and d). The measurement of the electrical resistance in as-implanted and annealed polymers is presented in Fig. 5a–c for PET, PI and PEEK, respectively. The resistance is a decreasing function of the ion fluence. The observed resistance evolution is comparable with that reported in [14,15]. After the annealing, the resistance further decreases in the case of PET and PEEK for implantation fluencies above 5 1016 cm 2 (see Fig. 5a). In PI, however, annealing does not change the electrical resistance significantly (see Fig. 5b).
investigations, the ion implantation, accompanied by polymer carbonisation, leads to a rapid decrease of electrical sheet resistance, which could be further decreased by annealing. Acknowledgements The research has been realised at the CANAM (Center of Accelerators and Nuclear Analytical Methods) infrastructure and has been supported by project No. P108/12/G108 and LM 2011019. References
4. Conclusions The structural and compositional changes of PET, PI and PEEK implanted by 40 keV Co+ ions and annealed at 200 °C for 20 min were studied using RBS and UV–vis spectroscopy. The measured as-implanted Co profiles differ from those simulated by the SRIM code, which does not take into account the gradual degradation of the polymer matrix during the implantation process. For all the polymers, the measured profile width is about twice as high as the simulated one. The annealing of the samples implanted at fluencies below 1.0 1016 cm 2 slightly influences the shape of the depth profiles and the position of the concentration maximum. The most pronounced profile change is observed on PET. It may be concluded that the annealing under the present conditions does not enhance the mobility of the implanted Co atoms much in PEEK and PI below an implantation fluence of 1.0 1016 cm 2. Specific changes in the polymer surface morphology are observed on AFM images, with the most significant ones occurring on PI implanted to different ion fluencies. The annealing causes an enhancement of the UV–vis absorbance of PEEK and PET implanted polymers, which could be connected to the structural changes followed by a decrease of electrical sheet resistance. In accordance with earlier
[1] A.L. Stepanov, R.I. Khaibullin, Rev. Adv. Mater. Sci. 7 (2004) 108–125. [2] F.S. Teixeira, M.C. Salvadori, M. Cattani, I.G. Brown, J. Appl. Phys. 105 (2009) 064313. [3] P. Malinsky, A. Mackova, V. Hnatowicz, R.I. Khaibullin, V.F. Valeev, P. Slepicka, V. Svorcik, M. Slouf, V. Perina, Nucl. Instr. Meth. Phys. Res. B 272 (2012) 396– 399. [4] J. Saarilahti, E. Rauhala, Nucl. Instr. Meth. Phys. Res. B64 (1992) 734. [5] IBANDL,