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Surface damage studies of ETFE polymer bombarded with low energy Si ions (⩽100 keV)
NIM B Beam Interactions with Materials & Atoms
Nuclear Instruments and Methods in Physics Research B 261 (2007) 1159–1161 www.elsevier.com/locate/nimb
Surface damage studies of ETFE polymer bombarded with low energy Si ions (6100 keV) Renato Amaral Minamisawa a, Adelaide De Almeida b, Satilmis Budak a, Volha Abidzina c, Daryush Ila a,* a
Center for Irradiation of Materials, Alabama A&M University, 4900 Meridian Street, Normal, AL 35762, USA b Departamento de Fisica, FFCLRP, Universidade de Sao Paulo, Ribeirao Preto, Sao Paulo, Brazil c Belarusian–Russian University, Mogilev, Belarus Available online 11 April 2007
Abstract Surface studies of ethylenetetrafluoroethylene (ETFE), bombarded with Si in a high-energy tandem Pelletron accelerator, have recently been reported. Si ion bombardment with a few MeV to a few hundred keV energies was shown to be sufficient to produce damage on ETFE film. We report here the use of a low energy implanter with Si ion energies lower than 100 keV, to induce changes on ETFE films. In order to determine the radiation damage, ETFE bombarded films were simulated with SRIM software and analyzed with optical absorption photometry (OAP), Raman and Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy to show quantitatively the physical and chemical property changes. Carbonization occurs following higher dose implantation, and hydroperoxides were formed following dehydroflorination of the polymer. 2007 Elsevier B.V. All rights reserved. PACS: 72.80.Le Keywords: ETFE; Polymer; Plasma; Radiation damage
1. Introduction A fluoropolymer is a polymer that contains atoms of fluorine, usually, polymerized tetrafluoroethylene. The resultant material has the lowest coefficient of friction of any known solid material and is inert to virtually all chemicals. ETFE is a polymer of ethylene and tetrafluoroethylene that uses a small amount of a modifier, often a thermonomer that gives the polymer unique thermal properties [1]. This polymer supports relatively high temperatures without deterioration and retains its properties at low temperature (100 K), can be processed by conventional thermoplastic techniques and is a flame retardant. It has good chemical and exceptional electrical resistance and also has higher impact, tensile strength and creep resistance than other fluorpolymers. *
Corresponding author. Tel.: +1 256 372 5877; fax: +1 256 372 8708. E-mail address: [email protected] (D. Ila).
0168-583X/$ - see front matter 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2007.04.034
ETFE has various applications, mainly, in the coating industry, in manufacturing, food and pharmaceutical packing, medical supplies and aerospace industries, as well as radiation dosimeters. In several of these applications the polymer is exposed to radiation, the damage from which will depend on the type, energy and intensity of radiation [2]. In this work, we report an investigation of the surface damage generated by Si ion implantation in ETFE polymer bombarded with energies that did not exceed 100 keV. The ion energy transferred to the polymer breaks the chains and releases atoms, creating vacancies [3,4]. Optical absorption photospectrometry (OAP), Raman spectroscopy and Fourier infrared transform attenuated total reflectance (FTIRATR) techniques will be used to determinate the chemical structure changes in the polymer. The results are useful for studies of radiation detection using the ETFE electret pattern state and for studies of the physical resistance of the polymer used for surface coating applications.
1160
R.A. Minamisawa et al. / Nucl. Instr. and Meth. in Phys. Res. B 261 (2007) 1159–1161
2. Materials and methods ETFE films with dimensions of 2.0 · 2.0 cm2 and 100 lm thick were bombarded using the AAMU-CIM low energy implanter NOVA with fluences of 1 · 1013, 1 · 1014, 1 · 1015, 1 · 1016 ions/cm2 for 100 keV Si and an extra fluence of 1 · 1017 ions/cm2 for 50 keV. The last fluence destroyed the material for 100 keV ion irradiation. The fluences were predicted evaluating the ETFE chemical characteristics and the SRIM 2003 simulation to define the limit of maximum damage supported by the material. In order to determine the damage products and structural changes in ETFE, optical analytical techniques were employed on the bombarded films after each fluence was accumulated, always comparing with the virgin sample. OAP measurements were performed using a Cary 5000 spectrophotometer. A Tensor 27 ATR-FTIR spectrometer equipped with the surface sensitive Pike-ATR accessory with a ZnSe crystal was employed to measure the ETFE bonds. The penetration of the evanescent wave is comparable with the implanted ion range reached in the species, minimizing the influence of the bulk substrate signal. In addition, Raman spectra were acquired using a LabRam spectrophotometer with a He–Ne laser (632.8 nm), also surface sensitive [5]. 3. Results and discussion The simulation of the 100 and 50 keV Si ion implantations were performed using SRIM 2003, which indicates a longitudinal range of 0.16 ± 0.03 lm and approximately 4780 vacancies produced per incident ion for 100 keV and 0.08 ± 0.02 lm longitudinal range and 1950 vacancies produced for 50 keV ion implantation in the ETFE thin film. The displacement energies for each atom of the polymeric matrix of ETFE [–CH2–CH2–CF2–CF2–] used in the simulation were calculated based in the chemical bond energies. The results of optical absorption photospectrometry are present in Fig. 1, which show the spectra obtained for virgin
2.0
films bombarded with accumulated fluences from 1015 to 1016 Si ions/cm2 for 100 keV irradiation, where only 1016 can be depicted. For lower fluences, no changes were observed. The spectrum for the virgin film indicates the presence of the normal single bonds in the polymer structure. The spectrum for ETFE bombarded with the fluence of 1 · 1016 ions/cm2 is slightly yellow giving the only visible indication of the formation of carbon double bonds and conjugated carbon bonds that absorb the blue light. These results are in agreement with previous observations of experiments with ion bombardment of ETFE using 100 keV Si [6]. The absorption is also a result of light scattered on the damaged surface because of the induced changes in roughness and in the implanted particles. No significant changes were observed in the samples irradiated with 50 keV Si ions. The results of the ATR-FTIR analysis are shown in Fig. 2. It is possible to observe the vibrations corresponding to characteristic peaks of the CF2 group in the range 1100–1400 cm 1 and the CH group in the range 900– 1100 cm 1. For fluences of 1013 to 1014 ions/cm2, there is no significant difference in the ATR spectra of the implanted and virgin samples. Beginning with 1014 for 100 keV and 1015 for 50 keV irradiation, there is an additional peak in 1100 cm 1, which is attributed to C–O, stretching vibration resulting from the formation of a small amount of hydroperoxides following the exposure to residual air in the implantation chamber. This bond is a consequence of hydrogen and fluorine leaving the polymer and allowing oxygen to attach to the dangling bonds [7,8]. Fig. 3 shows the Raman spectra comparing the effects of Si ion energy and fluence. The characteristic peaks of ETFE maintain their appearance up to the fluence of 1016 cm 2. This could be a sign of reduced damage due to implantation, but the Raman signal is believed to be collected from a depth more than that of the implanted layer and there may be a strong contribution of the virgin bulk material to this signal. The spectra for fluence 1016 cm 2 100 keV irradiation show a small peak at 1580 cm 1 due to graphitic formations.
100 keV Irradiation
1.2
50 keV Irradiation
1.8
Absorbance (A.U.)
1.4 1.2 1.0 0.8 0.6 0.4
Virgin Si-1e15/ETFE Si-1e16/ETFE Si-1e17/ETFE
1.0
Absorbance (A.U.)
Virgin Si-1e14/ETFE Si-1e15/ETFE Si-1e16/ETFE
1.6
0.8 0.6 0.4 0.2
0.2 0.0 200
400
Wavelength (nm)
600
0.0 200
400
Wavelength (nm)
Fig. 1. Optical absorption spectra of the implanted ETFE samples.
600
R.A. Minamisawa et al. / Nucl. Instr. and Meth. in Phys. Res. B 261 (2007) 1159–1161
50 keV Irradiation CF (1100-1400)cm -1 2
16
ion/cm
2
ETFE/10
15
ion/cm
2
ETFE/10
14
ion/cm
C-O
Absorbance (A.U.)
Absorbance (A.U.)
100 keV Irradiation CF 2 (1100-1400)cm -1 ETFE/10
2
ETFE/10
17
ion/cm
2
ETFE/10
16
ion/cm
2
ETFE/10
15
ion/cm
2
C-O
ETFE virgin
ETFE virgin
750
1161
1000
1250
1500
750
-1
1000
1250
1500
Wavenumber (cm-1)
Wavenumber (cm )
Fig. 2. ATR spectra of the implanted ETFE samples showing the appearance of C–O bonds at 1100 cm 1.
C-C streching
ETFE-virgin Si-1e17/ETFE
C-C streching 1580 cm
ETFE-virgin Si-1e15/ETFE
500
1000
ETFE-virgin Si-1e15/ETFE
Intensity (A.U.)
Intensity (A.U.)
ETFE-virgin Si-1e16/ETFE
CF CF2
ETFE-virgin Si-1e16/ETFE
-1
1580 cm
-1
ETFE-virgin Si-1e14/ETFE
ETFE-virgin Si-1e14/ETFE
CH2 scissoring
CF CF2
CH stretching
1500
3000
500
1000
ETFE-virgin Si-1e13/ETFE
CH2 scissoring CH stretching
1500
3000 -1
-1
Wavenumber (cm )
Wavenumber (cm )
Fig. 3. Raman spectra of the implanted ETFE samples: (a) Irradiated with 50 keV and (b) irradiated with 100 keV.
4. Conclusions We implanted Si ions with 100 and 50 keV in ETFE polymer films. The optical measurements performed on the implanted ETFE reveal low damage levels and little or no evidence of any chemical reaction between the implanted species and the host material. Although the Raman and FTIR analysis did not detect significant amounts of C–C bond, there is a certain degree of carbonization following higher dose implantation, indicated by the absorption of blue light in the UV-visible-near IR. FTIR measurements suggest the formation of hydroperoxides following dehydroflorination of the polymer. Acknowledgements This research was sponsored by the Center for Irradiation of Materials, Alabama A&M University and by the AAMURI Center for Advanced Propulsion Materials
under the Contract number NAG8-1933 from NASA, and by National Science Foundation under Grant No. EPS-0447675. References [1] G.M. Sessler, Introduction and Physical Principles of Electrets, in: G.M. Sessler (Ed.), Electrets, Springer–Verlag, New York, 1980. [2] M.A. Parada, A. de Almeida, Nucl. Instr. and Meth. B 191 (2002) 820. [3] A.L. Evelyn, D. Ila, R.L. Zimmerman, K. Bhat, D.B. Poker, D.K. Hensley, Mater. Res. Soc. Symp. Proc. 438 (1997) 499. [4] M.A. Parada, A. de Almeida, C. Muntele, I. Muntele, D. Ila, Surf. Coat. Technol. 196 (2005) 378. [5] C.R. Brundle, C.A. Evans Jr., S. Wilson, in: Encyclopedia of Materials Characterization: Surfaces, Interfaces, Thin Films, Butterworth– Heinemann, Boston, 1992. [6] R.A. Minamisawa, A. De Almeida, V. Abidzina, M.A. Parada, I. Muntele, D. Ila, Nucl. Instr. and Meth. 257 (2007) 568. [7] J. Brandup, E.H. Immergut, in: Polymer Handbook, third ed., John Wiley and Sons, USA, 1989. [8] N.B. Cothup, L.H. Daly, S.E. Wiberley, Introduction to Infrared and Raman Spectroscopy, third ed., Academic Press Inc., 1990.
Nuclear Instruments and Methods in Physics Research B 261 (2007) 1159–1161 www.elsevier.com/locate/nimb
Surface damage studies of ETFE polymer bombarded with low energy Si ions (6100 keV) Renato Amaral Minamisawa a, Adelaide De Almeida b, Satilmis Budak a, Volha Abidzina c, Daryush Ila a,* a
Center for Irradiation of Materials, Alabama A&M University, 4900 Meridian Street, Normal, AL 35762, USA b Departamento de Fisica, FFCLRP, Universidade de Sao Paulo, Ribeirao Preto, Sao Paulo, Brazil c Belarusian–Russian University, Mogilev, Belarus Available online 11 April 2007
Abstract Surface studies of ethylenetetrafluoroethylene (ETFE), bombarded with Si in a high-energy tandem Pelletron accelerator, have recently been reported. Si ion bombardment with a few MeV to a few hundred keV energies was shown to be sufficient to produce damage on ETFE film. We report here the use of a low energy implanter with Si ion energies lower than 100 keV, to induce changes on ETFE films. In order to determine the radiation damage, ETFE bombarded films were simulated with SRIM software and analyzed with optical absorption photometry (OAP), Raman and Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy to show quantitatively the physical and chemical property changes. Carbonization occurs following higher dose implantation, and hydroperoxides were formed following dehydroflorination of the polymer. 2007 Elsevier B.V. All rights reserved. PACS: 72.80.Le Keywords: ETFE; Polymer; Plasma; Radiation damage
1. Introduction A fluoropolymer is a polymer that contains atoms of fluorine, usually, polymerized tetrafluoroethylene. The resultant material has the lowest coefficient of friction of any known solid material and is inert to virtually all chemicals. ETFE is a polymer of ethylene and tetrafluoroethylene that uses a small amount of a modifier, often a thermonomer that gives the polymer unique thermal properties [1]. This polymer supports relatively high temperatures without deterioration and retains its properties at low temperature (100 K), can be processed by conventional thermoplastic techniques and is a flame retardant. It has good chemical and exceptional electrical resistance and also has higher impact, tensile strength and creep resistance than other fluorpolymers. *
Corresponding author. Tel.: +1 256 372 5877; fax: +1 256 372 8708. E-mail address: [email protected] (D. Ila).
0168-583X/$ - see front matter 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2007.04.034
ETFE has various applications, mainly, in the coating industry, in manufacturing, food and pharmaceutical packing, medical supplies and aerospace industries, as well as radiation dosimeters. In several of these applications the polymer is exposed to radiation, the damage from which will depend on the type, energy and intensity of radiation [2]. In this work, we report an investigation of the surface damage generated by Si ion implantation in ETFE polymer bombarded with energies that did not exceed 100 keV. The ion energy transferred to the polymer breaks the chains and releases atoms, creating vacancies [3,4]. Optical absorption photospectrometry (OAP), Raman spectroscopy and Fourier infrared transform attenuated total reflectance (FTIRATR) techniques will be used to determinate the chemical structure changes in the polymer. The results are useful for studies of radiation detection using the ETFE electret pattern state and for studies of the physical resistance of the polymer used for surface coating applications.
1160
R.A. Minamisawa et al. / Nucl. Instr. and Meth. in Phys. Res. B 261 (2007) 1159–1161
2. Materials and methods ETFE films with dimensions of 2.0 · 2.0 cm2 and 100 lm thick were bombarded using the AAMU-CIM low energy implanter NOVA with fluences of 1 · 1013, 1 · 1014, 1 · 1015, 1 · 1016 ions/cm2 for 100 keV Si and an extra fluence of 1 · 1017 ions/cm2 for 50 keV. The last fluence destroyed the material for 100 keV ion irradiation. The fluences were predicted evaluating the ETFE chemical characteristics and the SRIM 2003 simulation to define the limit of maximum damage supported by the material. In order to determine the damage products and structural changes in ETFE, optical analytical techniques were employed on the bombarded films after each fluence was accumulated, always comparing with the virgin sample. OAP measurements were performed using a Cary 5000 spectrophotometer. A Tensor 27 ATR-FTIR spectrometer equipped with the surface sensitive Pike-ATR accessory with a ZnSe crystal was employed to measure the ETFE bonds. The penetration of the evanescent wave is comparable with the implanted ion range reached in the species, minimizing the influence of the bulk substrate signal. In addition, Raman spectra were acquired using a LabRam spectrophotometer with a He–Ne laser (632.8 nm), also surface sensitive [5]. 3. Results and discussion The simulation of the 100 and 50 keV Si ion implantations were performed using SRIM 2003, which indicates a longitudinal range of 0.16 ± 0.03 lm and approximately 4780 vacancies produced per incident ion for 100 keV and 0.08 ± 0.02 lm longitudinal range and 1950 vacancies produced for 50 keV ion implantation in the ETFE thin film. The displacement energies for each atom of the polymeric matrix of ETFE [–CH2–CH2–CF2–CF2–] used in the simulation were calculated based in the chemical bond energies. The results of optical absorption photospectrometry are present in Fig. 1, which show the spectra obtained for virgin
2.0
films bombarded with accumulated fluences from 1015 to 1016 Si ions/cm2 for 100 keV irradiation, where only 1016 can be depicted. For lower fluences, no changes were observed. The spectrum for the virgin film indicates the presence of the normal single bonds in the polymer structure. The spectrum for ETFE bombarded with the fluence of 1 · 1016 ions/cm2 is slightly yellow giving the only visible indication of the formation of carbon double bonds and conjugated carbon bonds that absorb the blue light. These results are in agreement with previous observations of experiments with ion bombardment of ETFE using 100 keV Si [6]. The absorption is also a result of light scattered on the damaged surface because of the induced changes in roughness and in the implanted particles. No significant changes were observed in the samples irradiated with 50 keV Si ions. The results of the ATR-FTIR analysis are shown in Fig. 2. It is possible to observe the vibrations corresponding to characteristic peaks of the CF2 group in the range 1100–1400 cm 1 and the CH group in the range 900– 1100 cm 1. For fluences of 1013 to 1014 ions/cm2, there is no significant difference in the ATR spectra of the implanted and virgin samples. Beginning with 1014 for 100 keV and 1015 for 50 keV irradiation, there is an additional peak in 1100 cm 1, which is attributed to C–O, stretching vibration resulting from the formation of a small amount of hydroperoxides following the exposure to residual air in the implantation chamber. This bond is a consequence of hydrogen and fluorine leaving the polymer and allowing oxygen to attach to the dangling bonds [7,8]. Fig. 3 shows the Raman spectra comparing the effects of Si ion energy and fluence. The characteristic peaks of ETFE maintain their appearance up to the fluence of 1016 cm 2. This could be a sign of reduced damage due to implantation, but the Raman signal is believed to be collected from a depth more than that of the implanted layer and there may be a strong contribution of the virgin bulk material to this signal. The spectra for fluence 1016 cm 2 100 keV irradiation show a small peak at 1580 cm 1 due to graphitic formations.
100 keV Irradiation
1.2
50 keV Irradiation
1.8
Absorbance (A.U.)
1.4 1.2 1.0 0.8 0.6 0.4
Virgin Si-1e15/ETFE Si-1e16/ETFE Si-1e17/ETFE
1.0
Absorbance (A.U.)
Virgin Si-1e14/ETFE Si-1e15/ETFE Si-1e16/ETFE
1.6
0.8 0.6 0.4 0.2
0.2 0.0 200
400
Wavelength (nm)
600
0.0 200
400
Wavelength (nm)
Fig. 1. Optical absorption spectra of the implanted ETFE samples.
600
R.A. Minamisawa et al. / Nucl. Instr. and Meth. in Phys. Res. B 261 (2007) 1159–1161
50 keV Irradiation CF (1100-1400)cm -1 2
16
ion/cm
2
ETFE/10
15
ion/cm
2
ETFE/10
14
ion/cm
C-O
Absorbance (A.U.)
Absorbance (A.U.)
100 keV Irradiation CF 2 (1100-1400)cm -1 ETFE/10
2
ETFE/10
17
ion/cm
2
ETFE/10
16
ion/cm
2
ETFE/10
15
ion/cm
2
C-O
ETFE virgin
ETFE virgin
750
1161
1000
1250
1500
750
-1
1000
1250
1500
Wavenumber (cm-1)
Wavenumber (cm )
Fig. 2. ATR spectra of the implanted ETFE samples showing the appearance of C–O bonds at 1100 cm 1.
C-C streching
ETFE-virgin Si-1e17/ETFE
C-C streching 1580 cm
ETFE-virgin Si-1e15/ETFE
500
1000
ETFE-virgin Si-1e15/ETFE
Intensity (A.U.)
Intensity (A.U.)
ETFE-virgin Si-1e16/ETFE
CF CF2
ETFE-virgin Si-1e16/ETFE
-1
1580 cm
-1
ETFE-virgin Si-1e14/ETFE
ETFE-virgin Si-1e14/ETFE
CH2 scissoring
CF CF2
CH stretching
1500
3000
500
1000
ETFE-virgin Si-1e13/ETFE
CH2 scissoring CH stretching
1500
3000 -1
-1
Wavenumber (cm )
Wavenumber (cm )
Fig. 3. Raman spectra of the implanted ETFE samples: (a) Irradiated with 50 keV and (b) irradiated with 100 keV.
4. Conclusions We implanted Si ions with 100 and 50 keV in ETFE polymer films. The optical measurements performed on the implanted ETFE reveal low damage levels and little or no evidence of any chemical reaction between the implanted species and the host material. Although the Raman and FTIR analysis did not detect significant amounts of C–C bond, there is a certain degree of carbonization following higher dose implantation, indicated by the absorption of blue light in the UV-visible-near IR. FTIR measurements suggest the formation of hydroperoxides following dehydroflorination of the polymer. Acknowledgements This research was sponsored by the Center for Irradiation of Materials, Alabama A&M University and by the AAMURI Center for Advanced Propulsion Materials
under the Contract number NAG8-1933 from NASA, and by National Science Foundation under Grant No. EPS-0447675. References [1] G.M. Sessler, Introduction and Physical Principles of Electrets, in: G.M. Sessler (Ed.), Electrets, Springer–Verlag, New York, 1980. [2] M.A. Parada, A. de Almeida, Nucl. Instr. and Meth. B 191 (2002) 820. [3] A.L. Evelyn, D. Ila, R.L. Zimmerman, K. Bhat, D.B. Poker, D.K. Hensley, Mater. Res. Soc. Symp. Proc. 438 (1997) 499. [4] M.A. Parada, A. de Almeida, C. Muntele, I. Muntele, D. Ila, Surf. Coat. Technol. 196 (2005) 378. [5] C.R. Brundle, C.A. Evans Jr., S. Wilson, in: Encyclopedia of Materials Characterization: Surfaces, Interfaces, Thin Films, Butterworth– Heinemann, Boston, 1992. [6] R.A. Minamisawa, A. De Almeida, V. Abidzina, M.A. Parada, I. Muntele, D. Ila, Nucl. Instr. and Meth. 257 (2007) 568. [7] J. Brandup, E.H. Immergut, in: Polymer Handbook, third ed., John Wiley and Sons, USA, 1989. [8] N.B. Cothup, L.H. Daly, S.E. Wiberley, Introduction to Infrared and Raman Spectroscopy, third ed., Academic Press Inc., 1990.