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polymer films deposited on pet substrates by RF reactive magnetron sputtering
Vacuum 89 (2013) 109e112
Contents lists available at SciVerse ScienceDirect
Vacuum journal homepage: www.elsevier.com/locate/vacuum
Characterization of composite SiOx/polymer films deposited on pet substrates by RF reactive magnetron sputtering Zhuang Liu a, b, *, Xinxin Ma a, ChunLi Yang b, Fangjun Xu a a b
School of Material Science and Engineering, Harbin Institute of Technology, Harbin 150001, China School of Light Industry, Harbin University of Commerce, Harbin 150028, China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 22 September 2011 Received in revised form 4 January 2012 Accepted 23 February 2012
Composite SiOx/polymer films have been prepared on polyethylene terephthalate (PET) substrates by radio frequency (RF) reactive magnetron co-sputtering, from which two balanced magnetrons are equipped with silica and dicyclopentadiene dioxide cured with maleic anhydride (DCPD/MA) targets. Morphology and composition of the deposited composite films have been analyzed by means of AFM, FTIR, and XPS. The influences of preparation procedure parameters, primarily including RF power densities and the ratio of RF powers delivered to the two targets, on the obtained films properties such as surface roughness, water vapor/oxygen transmission rate and flexibility have been investigated. As PDCPD=MA =PSiO2 , the ratio of RF powers delivered to the individual target changed from 0.13 to 7.5, the roughness of films decreases from 2.793 nm down to 0.9 nm and the numbers of cracks produced in the films after folding are reduced dramatically. At the ratio of RF power of 3, higher RF power densities and lower work pressure have better performance in preventing the permeation of water vapor and oxygen. The minimum transmission rates of water vapor and oxygen are 0.26 g/m2/24 h atm and 0.38 cc/m2/ day atm, respectively. Ó 2012 Elsevier Ltd. All rights reserved.
Keywords: Composite films Magnetron co-sputtering Polyethylene terephthalate (PET) Dicyclopentadiene dioxide
1. Introduction Polymers used as target in RF magnetron sputtering started from 1970s [1,2], of which polytetrafluoroethylene (PTFE) was mostly focused on and hydrocarbon targets such as polyethylene (PE) and polypropylene (PP) had also been investigated [3,4]. As the polymeric targets being sputtered, the polymer fragments are released from the targets and these fragments react and deposit on surfaces of the substrates. The films prepared by sputtering polymeric targets have similar compositions and structures to the targets. The coatings were apparently to prepare good dielectric films and low friction coatings. Optical applications were also considered. Recently, the more complicated composite films as protective coatings were prepared by RF magnetron co-sputtering polymer and SiO2 targets, such as SiO2/PTFE, SiO2/PI targets [5e7]. However, the preparations of polymer/inorganic composite coatings by magnetron sputtering are still in an initial research stage. Hence, the studies for preparing new polymer/inorganic composite are
* Corresponding author. School of Material Science and Engineering, Harbin Institute of Technology, West Da-Zhi Street, Harbin 150001, China. E-mail address: [email protected] (Z. Liu). 0042-207X/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.vacuum.2012.02.035
very important and promising. In previous works, few reports about barrier properties of composite films were reached. Therefore, we decided to prepare SiOx/polymer composite films by RF cosputtering form the two magnetrons equipped with SiO2 and DCPD/MA targets. The properties of SiOx/polymer composite films were investigated. 2. Experimental part A roll-to-roll web coating machine (JRJ-400, Beijing Orient Gide vacuum technology Co. Ltd) was used to deposited composite films on polyethylene terephthalate (PET) substrates. The device can handle webs with a width of up to 400 mm, and the rotation rate is adjustable between 100 and 5000 mm/min. The film thickness can be controlled by adjusting the rotation rate and the number of repetition of deposition. A SiO2 target in size of 600 120 mm2 and purity of 99.999% was set at the bottom of the vacuum chamber, and the distance between the target and the matrix fixed at 100 mm. Another polymer target, dicyclopentadiene dioxide cured with maleic anhydride (DCPD/MA), was equipped beside SiO2 target. Argon in purity of 99.99% was used for sputtering. The pressure in vacuum chamber was 103 Pa prior to sputtering, and the
110
Z. Liu et al. / Vacuum 89 (2013) 109e112 Table 1 Concentration of elements (at%). Ratio of RF power
Si
C
O
PDCPD=MA =PSiO2 PDCPD=MA =PSiO2 PDCPD=MA =PSiO2 PDCPD=MA =PSiO2
31.8 26.7 23.2 10.7
7.1 20.8 29.5 49.7
61.1 52.5 46.3 39.6
¼ ¼ ¼ ¼
0.13 1.5 3.0 7.5
3. Results and discussion 3.1. Deposition rate
Fig. 1. FTIR spectra of the films deposited at different PDCPD=MA =PSiO2 power ratios (a) 3, (b) 0.13, (c) 7.5.
In order to compare the deposition rate of composite SiOx/ polymer with that of SiOx coatings, the measurements of deposition rates of pure SiO2 and DCPD/MA were performed under the same conditions. Film thickness was measured by profilometry. It is well known that deposition rate of SiO2 is lower in comparison with polymers such as PTFE, PI, which were the same with DCPD/MA used as target. The deposition rate was around of 15 nm/min at the 3.6 W/cm2 of RF power density. 3.2. Structure of the composite films determined by FTIR
operating pressure was at 0.9 Pa. The range of RF power delivered to the SiO2 targets was from 100 W to 3000 W, and the range delivered to the DCPD/MA from 100 W to 1500 W. The chemical properties of the deposition SiOx/polymer films were characterized by using Fourier Transform Infrared (FTIR) with a resolution of 4 cm1 and AXIS Ultra X-ray photoelectron spectroscopy (XPS) with a energy resolution of 0.48 eV(Ag3d5/2), an operating voltage of 15 kV and a radiate current of 15 mA. The pressure during analysis was 1 109 mbar. Atomic force microscope (AFM) was performed to obtain the surface morphology and thickness of the coatings. The water vapor transmission rate (WVTR) was measured using a Permatran (MOCON Co., W1/50) with a sample size of 50 cm2 and a resolution of 0.001 g/m2/24 h. The oxygen transmission rate (OTR) was measured using an OX-tran (MOCON Co., 2/21) with a sample size of 50 cm2 and a resolution of 0.000001 cc/m2/day. The former measurements were taken at atmospheric pressure and an 100% relative humidity (RH), the latter at the same pressure and 0% RH. The flexion tests were carried out by means of self-developed equipment. Samples were set at two opposite sides on metals rods moved forwards and backwards oppositely. SEM observations were made after the flexion test.
Since SiOx/polymer composite films being transparent, the FTIR measurement with ATR accessory was carried out to investigate the change of the chemical structure of the obtained films at different PDCPD=MA =PSiO2 ratio. The absorption bands are identified in Fig. 1. The films have a complex chemical structure. The intensive asymmetric SieOeSi
Fig. 3. OTR and WVTR dependence on the power ratio PDCPD=MA =PSiO2 .
Fig. 2. XPS spectra (a) Si 2p, (b) C 1s at different PDCPD=MA =PSiO2 power ratios.
Z. Liu et al. / Vacuum 89 (2013) 109e112
111
Fig. 4. The SEM micrographs of SiOx (a) and SiOx/polymer (b) after 100 cycles.
and SieO stretching vibrations were detected at 1030e1190 and 650 cm1, on the other hand bending SieOeSi vibrations at 800e810 cm1. In the FTIR spectrum (see Fig. 1c), the epoxy group vibration was detected at 834 cm1. As PDCPD=MA =PSiO2 ratio being 3, this peak was weaken (illustrated in Fig. 1a); as ratio being 0.13, it disappeared. From the above information we could infer that the films deposited by co-sputtering the DCPD/MA and SiO2 targets contained epoxy molecular groups and the cross-linking phenomena between SieO and epoxy groups. 3.3. XPS analysis of composite SiOx/polymer films The XPS measurements have been performed in order to calculate the elemental content of SiOx/polymer films, observe the building of chemical bonds and reveal the relations between silicon content and the values of PDCPD=MA =PSiO2 ratio. Decrease of the PDCPD=MA =PSiO2 ratio leads to an increase in the silicon content, which can be deduced from the Si 2p data shown in Fig. 2a. The intensity of this peak decreases with increasing DCPD/MA content and reaches the lowest value at the power ratio PDCPD=MA =PSiO2 ¼ 7.5. The elemental concentrations calculated from the area of the Si 2p and C 1s peaks shows that the content of silicon decreases from 31.8% to 10.7% and content of carbon increases from 8.1% to 49.7% when the RF power ratio PDCPD=MA =PSiO2 increases from 0.13 to 7.5 (Table 1). Apparently, a low PDCPD=MA =PSiO2 ratio produces more SiO2-like coatings, which is accordance with the spectra measured by FTIR, discussed in the previous section. Fig. 2b shows the C 1s core levels measured for the samples deposited with different power ratio of PDCPD=MA =PSiO2 . Carbon bound to silicon might also contribute to the main component. However, obviously the difference between CeC and CeSi chemical shifts in C 1s cannot be resolved because of the close binding energies of these bonds. Therefore, the contribution of CeSi bonds to the C 1s peak are ignored. The Si 2p peak positions of Si0, Si1þ, Si2þ, Si3þ and Si4þ in SiOx are 99.7, 100.6, 101.6, 102.7 and 103.8 eV [8], which indicates that the most silicon of composite films is bound to oxygen due to the peak of Si 2p appearing at 103.3e103.7 eV (Fig. 2a). From the comparison C 1s peak components of different samples shown in Fig. 2b, the peaks between 288.3and 288.5 eV are more apparent with SiO2 content higher. Sample with higher PDCPD=MA =PSiO2 ratio show more CeC bonds .The higher binding energy of C 1s indicates that the carbon might have been oxidized and assigned to C]O, CeOeC, and OeC]O functional groups [7].
from the AFM scans. It decreased from 2.79 nm of the films with a high amount of SiOx prepared at the power ratio PDCPD=MA =PSiO2 ¼ 0.13 down to values of 0.9 nm of the films that have a more polymeric content prepared at the power ratio PDCPD=MA =PSiO2 ¼ 7.5. 3.5. The barrier properties of films Moisture and oxygen could cause food deterioration and electronic device aging, therefore the barrier to water vapor and oxygen is one of the critical characteristics. The permeation rates of water vapor and oxygen through the SiOx/polymer composite layers are shown in Fig. 3. It’s clear that the OTR and WVTR of SiOx/polymer decrease dramatically in comparison with uncoated PET. SiOx/polymer films compared with SiOx have better barrier ability from oxygen and water vapor, perhaps because the roughness of SiOx/polymer is lower than that of SiOx films, which indicates the defect concentration in co-sputtering SiOx/polymer network is lower than that in the single targets sputtering SiOx network. Thus, the co-sputtering SiOx/polymer films evidently increase the network compactness. 3.6. Flexion tests Fig. 4 shows the SEM micrographs of SiOx deposited at 2500 W and SiOx/polymer films deposited at PDCPD=MA =PSiO2 ¼ 3 after folding cycles. Parallel patterns of cracks of the SiOx films after the flexion test are apparent. This feature will significantly degrade the permeation behavior of water vapor and oxygen [9]. However, SiOx/ polymer films deposited at PDCPD=MA =PSiO2 ¼ 3 are folded after 100 times and no cracks produce on the films shown in Fig. 4b, which indicates the DCPD/MA increases dramatically the flexibility of SiOx films. 4. Conclusion It has been shown that composite polymer/SiOx can be prepared by RF co-sputtering from the two SiO2 and DCPD/MA targets. The roughness of films is low (0.9 nm). The barrier properties of PET are mostly improved, and the minimum transmission rates of water vapor and oxygen are 0.26 g/m2/24 h atm and 0.38 cc/m2/day atm, respectively. The barrier properties of composite films being folded are stable.
3.4. Morphology of films examined using AFM
References
The examination of the morphology of the prepared composite films was done by AFM. The roughness of the films was estimated
[1] Biederman H, Stelmashuk V, Kholodkov I, Choukourov A, Slavínská D. RF sputtering of hydrocarbon polymers and their derivatives. Surf Coat Technol 2003;174e175:27e32.
112
Z. Liu et al. / Vacuum 89 (2013) 109e112
[2] Biederman H. RF sputtering of polymers and its potential application. Vacuum 2000;59:594e9. [3] Stelmashuk V, Biederman H, Slavínská D, Trchová M, Hlidek P. RF magnetron sputtering of polypropylene. Vacuum 2004;75:207e15. [4] Kousal J, Hanus TJ, Choukourov A, Hlídek P, Biederman H, Slavínská D, et al. RF magnetron sputtering and evaporation of polyisobutylene and low density polyethylene. Surf Coat Technol 2005;200:472e5. [5] Drabik M, Kousal J, Pihosh Y, Choukourov A, Biedermana H, Slavinska D, et al. Composite SiO x/hydrocarbon plasma polymer films prepared by RF magnetron sputtering of SiO 2 and polyimide. Vacuum 2007;81:920e7.
[6] Pihosh Y, Biederman H, Slavinska D, Kousal J, Choukourova A, Trchova M, et al. Composite SiOx/fluorocarbon plasma polymer films prepared by r.f. magnetron sputtering of SiO2 and PTFE. Vacuum 2006;81:38e44. [7] Pihosh Y, Biederman H, Slavinska D, Kousal J, Choukourov A, Trchova M, et al. Composite SiOx/hydrocarbon plasma polymer films prepared by RF magnetron sputtering of SiO2 and polyethylene or polypropylene. Vacuum 2006;81:32e7. [8] Miyazaki H, Goto T. SiOx films prepared using RF magnetron sputtering with a SiO target. J Non-Crystalline Solids 2006;352:329e33. [9] Lin MC, Tseng CH, Chang LS, Wuu DS. Characterization of the silicon oxide thin films deposited on polyethylene terephthalate substrates by radio frequency reactive magnetron sputtering. Thin Solid Films 2007;515:4596e602.
Contents lists available at SciVerse ScienceDirect
Vacuum journal homepage: www.elsevier.com/locate/vacuum
Characterization of composite SiOx/polymer films deposited on pet substrates by RF reactive magnetron sputtering Zhuang Liu a, b, *, Xinxin Ma a, ChunLi Yang b, Fangjun Xu a a b
School of Material Science and Engineering, Harbin Institute of Technology, Harbin 150001, China School of Light Industry, Harbin University of Commerce, Harbin 150028, China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 22 September 2011 Received in revised form 4 January 2012 Accepted 23 February 2012
Composite SiOx/polymer films have been prepared on polyethylene terephthalate (PET) substrates by radio frequency (RF) reactive magnetron co-sputtering, from which two balanced magnetrons are equipped with silica and dicyclopentadiene dioxide cured with maleic anhydride (DCPD/MA) targets. Morphology and composition of the deposited composite films have been analyzed by means of AFM, FTIR, and XPS. The influences of preparation procedure parameters, primarily including RF power densities and the ratio of RF powers delivered to the two targets, on the obtained films properties such as surface roughness, water vapor/oxygen transmission rate and flexibility have been investigated. As PDCPD=MA =PSiO2 , the ratio of RF powers delivered to the individual target changed from 0.13 to 7.5, the roughness of films decreases from 2.793 nm down to 0.9 nm and the numbers of cracks produced in the films after folding are reduced dramatically. At the ratio of RF power of 3, higher RF power densities and lower work pressure have better performance in preventing the permeation of water vapor and oxygen. The minimum transmission rates of water vapor and oxygen are 0.26 g/m2/24 h atm and 0.38 cc/m2/ day atm, respectively. Ó 2012 Elsevier Ltd. All rights reserved.
Keywords: Composite films Magnetron co-sputtering Polyethylene terephthalate (PET) Dicyclopentadiene dioxide
1. Introduction Polymers used as target in RF magnetron sputtering started from 1970s [1,2], of which polytetrafluoroethylene (PTFE) was mostly focused on and hydrocarbon targets such as polyethylene (PE) and polypropylene (PP) had also been investigated [3,4]. As the polymeric targets being sputtered, the polymer fragments are released from the targets and these fragments react and deposit on surfaces of the substrates. The films prepared by sputtering polymeric targets have similar compositions and structures to the targets. The coatings were apparently to prepare good dielectric films and low friction coatings. Optical applications were also considered. Recently, the more complicated composite films as protective coatings were prepared by RF magnetron co-sputtering polymer and SiO2 targets, such as SiO2/PTFE, SiO2/PI targets [5e7]. However, the preparations of polymer/inorganic composite coatings by magnetron sputtering are still in an initial research stage. Hence, the studies for preparing new polymer/inorganic composite are
* Corresponding author. School of Material Science and Engineering, Harbin Institute of Technology, West Da-Zhi Street, Harbin 150001, China. E-mail address: [email protected] (Z. Liu). 0042-207X/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.vacuum.2012.02.035
very important and promising. In previous works, few reports about barrier properties of composite films were reached. Therefore, we decided to prepare SiOx/polymer composite films by RF cosputtering form the two magnetrons equipped with SiO2 and DCPD/MA targets. The properties of SiOx/polymer composite films were investigated. 2. Experimental part A roll-to-roll web coating machine (JRJ-400, Beijing Orient Gide vacuum technology Co. Ltd) was used to deposited composite films on polyethylene terephthalate (PET) substrates. The device can handle webs with a width of up to 400 mm, and the rotation rate is adjustable between 100 and 5000 mm/min. The film thickness can be controlled by adjusting the rotation rate and the number of repetition of deposition. A SiO2 target in size of 600 120 mm2 and purity of 99.999% was set at the bottom of the vacuum chamber, and the distance between the target and the matrix fixed at 100 mm. Another polymer target, dicyclopentadiene dioxide cured with maleic anhydride (DCPD/MA), was equipped beside SiO2 target. Argon in purity of 99.99% was used for sputtering. The pressure in vacuum chamber was 103 Pa prior to sputtering, and the
110
Z. Liu et al. / Vacuum 89 (2013) 109e112 Table 1 Concentration of elements (at%). Ratio of RF power
Si
C
O
PDCPD=MA =PSiO2 PDCPD=MA =PSiO2 PDCPD=MA =PSiO2 PDCPD=MA =PSiO2
31.8 26.7 23.2 10.7
7.1 20.8 29.5 49.7
61.1 52.5 46.3 39.6
¼ ¼ ¼ ¼
0.13 1.5 3.0 7.5
3. Results and discussion 3.1. Deposition rate
Fig. 1. FTIR spectra of the films deposited at different PDCPD=MA =PSiO2 power ratios (a) 3, (b) 0.13, (c) 7.5.
In order to compare the deposition rate of composite SiOx/ polymer with that of SiOx coatings, the measurements of deposition rates of pure SiO2 and DCPD/MA were performed under the same conditions. Film thickness was measured by profilometry. It is well known that deposition rate of SiO2 is lower in comparison with polymers such as PTFE, PI, which were the same with DCPD/MA used as target. The deposition rate was around of 15 nm/min at the 3.6 W/cm2 of RF power density. 3.2. Structure of the composite films determined by FTIR
operating pressure was at 0.9 Pa. The range of RF power delivered to the SiO2 targets was from 100 W to 3000 W, and the range delivered to the DCPD/MA from 100 W to 1500 W. The chemical properties of the deposition SiOx/polymer films were characterized by using Fourier Transform Infrared (FTIR) with a resolution of 4 cm1 and AXIS Ultra X-ray photoelectron spectroscopy (XPS) with a energy resolution of 0.48 eV(Ag3d5/2), an operating voltage of 15 kV and a radiate current of 15 mA. The pressure during analysis was 1 109 mbar. Atomic force microscope (AFM) was performed to obtain the surface morphology and thickness of the coatings. The water vapor transmission rate (WVTR) was measured using a Permatran (MOCON Co., W1/50) with a sample size of 50 cm2 and a resolution of 0.001 g/m2/24 h. The oxygen transmission rate (OTR) was measured using an OX-tran (MOCON Co., 2/21) with a sample size of 50 cm2 and a resolution of 0.000001 cc/m2/day. The former measurements were taken at atmospheric pressure and an 100% relative humidity (RH), the latter at the same pressure and 0% RH. The flexion tests were carried out by means of self-developed equipment. Samples were set at two opposite sides on metals rods moved forwards and backwards oppositely. SEM observations were made after the flexion test.
Since SiOx/polymer composite films being transparent, the FTIR measurement with ATR accessory was carried out to investigate the change of the chemical structure of the obtained films at different PDCPD=MA =PSiO2 ratio. The absorption bands are identified in Fig. 1. The films have a complex chemical structure. The intensive asymmetric SieOeSi
Fig. 3. OTR and WVTR dependence on the power ratio PDCPD=MA =PSiO2 .
Fig. 2. XPS spectra (a) Si 2p, (b) C 1s at different PDCPD=MA =PSiO2 power ratios.
Z. Liu et al. / Vacuum 89 (2013) 109e112
111
Fig. 4. The SEM micrographs of SiOx (a) and SiOx/polymer (b) after 100 cycles.
and SieO stretching vibrations were detected at 1030e1190 and 650 cm1, on the other hand bending SieOeSi vibrations at 800e810 cm1. In the FTIR spectrum (see Fig. 1c), the epoxy group vibration was detected at 834 cm1. As PDCPD=MA =PSiO2 ratio being 3, this peak was weaken (illustrated in Fig. 1a); as ratio being 0.13, it disappeared. From the above information we could infer that the films deposited by co-sputtering the DCPD/MA and SiO2 targets contained epoxy molecular groups and the cross-linking phenomena between SieO and epoxy groups. 3.3. XPS analysis of composite SiOx/polymer films The XPS measurements have been performed in order to calculate the elemental content of SiOx/polymer films, observe the building of chemical bonds and reveal the relations between silicon content and the values of PDCPD=MA =PSiO2 ratio. Decrease of the PDCPD=MA =PSiO2 ratio leads to an increase in the silicon content, which can be deduced from the Si 2p data shown in Fig. 2a. The intensity of this peak decreases with increasing DCPD/MA content and reaches the lowest value at the power ratio PDCPD=MA =PSiO2 ¼ 7.5. The elemental concentrations calculated from the area of the Si 2p and C 1s peaks shows that the content of silicon decreases from 31.8% to 10.7% and content of carbon increases from 8.1% to 49.7% when the RF power ratio PDCPD=MA =PSiO2 increases from 0.13 to 7.5 (Table 1). Apparently, a low PDCPD=MA =PSiO2 ratio produces more SiO2-like coatings, which is accordance with the spectra measured by FTIR, discussed in the previous section. Fig. 2b shows the C 1s core levels measured for the samples deposited with different power ratio of PDCPD=MA =PSiO2 . Carbon bound to silicon might also contribute to the main component. However, obviously the difference between CeC and CeSi chemical shifts in C 1s cannot be resolved because of the close binding energies of these bonds. Therefore, the contribution of CeSi bonds to the C 1s peak are ignored. The Si 2p peak positions of Si0, Si1þ, Si2þ, Si3þ and Si4þ in SiOx are 99.7, 100.6, 101.6, 102.7 and 103.8 eV [8], which indicates that the most silicon of composite films is bound to oxygen due to the peak of Si 2p appearing at 103.3e103.7 eV (Fig. 2a). From the comparison C 1s peak components of different samples shown in Fig. 2b, the peaks between 288.3and 288.5 eV are more apparent with SiO2 content higher. Sample with higher PDCPD=MA =PSiO2 ratio show more CeC bonds .The higher binding energy of C 1s indicates that the carbon might have been oxidized and assigned to C]O, CeOeC, and OeC]O functional groups [7].
from the AFM scans. It decreased from 2.79 nm of the films with a high amount of SiOx prepared at the power ratio PDCPD=MA =PSiO2 ¼ 0.13 down to values of 0.9 nm of the films that have a more polymeric content prepared at the power ratio PDCPD=MA =PSiO2 ¼ 7.5. 3.5. The barrier properties of films Moisture and oxygen could cause food deterioration and electronic device aging, therefore the barrier to water vapor and oxygen is one of the critical characteristics. The permeation rates of water vapor and oxygen through the SiOx/polymer composite layers are shown in Fig. 3. It’s clear that the OTR and WVTR of SiOx/polymer decrease dramatically in comparison with uncoated PET. SiOx/polymer films compared with SiOx have better barrier ability from oxygen and water vapor, perhaps because the roughness of SiOx/polymer is lower than that of SiOx films, which indicates the defect concentration in co-sputtering SiOx/polymer network is lower than that in the single targets sputtering SiOx network. Thus, the co-sputtering SiOx/polymer films evidently increase the network compactness. 3.6. Flexion tests Fig. 4 shows the SEM micrographs of SiOx deposited at 2500 W and SiOx/polymer films deposited at PDCPD=MA =PSiO2 ¼ 3 after folding cycles. Parallel patterns of cracks of the SiOx films after the flexion test are apparent. This feature will significantly degrade the permeation behavior of water vapor and oxygen [9]. However, SiOx/ polymer films deposited at PDCPD=MA =PSiO2 ¼ 3 are folded after 100 times and no cracks produce on the films shown in Fig. 4b, which indicates the DCPD/MA increases dramatically the flexibility of SiOx films. 4. Conclusion It has been shown that composite polymer/SiOx can be prepared by RF co-sputtering from the two SiO2 and DCPD/MA targets. The roughness of films is low (0.9 nm). The barrier properties of PET are mostly improved, and the minimum transmission rates of water vapor and oxygen are 0.26 g/m2/24 h atm and 0.38 cc/m2/day atm, respectively. The barrier properties of composite films being folded are stable.
3.4. Morphology of films examined using AFM
References
The examination of the morphology of the prepared composite films was done by AFM. The roughness of the films was estimated
[1] Biederman H, Stelmashuk V, Kholodkov I, Choukourov A, Slavínská D. RF sputtering of hydrocarbon polymers and their derivatives. Surf Coat Technol 2003;174e175:27e32.
112
Z. Liu et al. / Vacuum 89 (2013) 109e112
[2] Biederman H. RF sputtering of polymers and its potential application. Vacuum 2000;59:594e9. [3] Stelmashuk V, Biederman H, Slavínská D, Trchová M, Hlidek P. RF magnetron sputtering of polypropylene. Vacuum 2004;75:207e15. [4] Kousal J, Hanus TJ, Choukourov A, Hlídek P, Biederman H, Slavínská D, et al. RF magnetron sputtering and evaporation of polyisobutylene and low density polyethylene. Surf Coat Technol 2005;200:472e5. [5] Drabik M, Kousal J, Pihosh Y, Choukourov A, Biedermana H, Slavinska D, et al. Composite SiO x/hydrocarbon plasma polymer films prepared by RF magnetron sputtering of SiO 2 and polyimide. Vacuum 2007;81:920e7.
[6] Pihosh Y, Biederman H, Slavinska D, Kousal J, Choukourova A, Trchova M, et al. Composite SiOx/fluorocarbon plasma polymer films prepared by r.f. magnetron sputtering of SiO2 and PTFE. Vacuum 2006;81:38e44. [7] Pihosh Y, Biederman H, Slavinska D, Kousal J, Choukourov A, Trchova M, et al. Composite SiOx/hydrocarbon plasma polymer films prepared by RF magnetron sputtering of SiO2 and polyethylene or polypropylene. Vacuum 2006;81:32e7. [8] Miyazaki H, Goto T. SiOx films prepared using RF magnetron sputtering with a SiO target. J Non-Crystalline Solids 2006;352:329e33. [9] Lin MC, Tseng CH, Chang LS, Wuu DS. Characterization of the silicon oxide thin films deposited on polyethylene terephthalate substrates by radio frequency reactive magnetron sputtering. Thin Solid Films 2007;515:4596e602.