- Email: [email protected]
Transparent carbon nanotube coatings
Applied Surface Science 252 (2005) 425–429 www.elsevier.com/locate/apsusc
Transparent carbon nanotube coatings M. Kaempgen a,*, G.S. Duesberg b, S. Roth a a
Max-Planck-Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany b Infineon Technologies, Corporate Research, Otto-Hahn-Ring 6, 81739 Munich, Germany
Received 5 January 2005; received in revised form 14 January 2005; accepted 16 January 2005 Available online 10 February 2005
Abstract Thin networks of carbon nanotubes (CNTs) are sprayed onto glass or plastic substrates in order to obtain conductive transparent coatings. Transparency and conductivity at room temperature of different CNT material are evaluated. CNT coatings maintain their properties under mechanical stress, even after folding the substrate. At a transparency of 90% for visible light we observe a surface resistivity of 1 kV/sq which is already a promising value for various applications. # 2005 Elsevier B.V. All rights reserved. Keywords: Carbon nanotubes; Transparent electrodes; ITO
Conductivity and high aspect ratio of carbon nanotubes (CNTs) are attractive properties for producing conductive composites with a minimum of material. This feature can be used in coatings to get transparent and conductive networks. There is an increasing interest in thin transparent networks since it has been demonstrated that they can be used for more than basic investigations [1–7]. There is also an upcoming potential for several applications such as transistors [8–11], diodes [12], sensors [13,14], optical modulators [15] or as conductive backbone for electrochemical polymer coating [16]. Since electronic and optical properties vary with CNT material, we started a comparative * Corresponding author. Tel.: +49 711 6891401; fax: +49 711 6891010. E-mail address: [email protected] (M. Kaempgen).
study on different CNT material in terms of simple conductive coatings. So far, several methods are used in order to get thin CNT networks such as filtration [7,15], drying from solvent [17], spin coating [11] or Langmuir–Blodgett [18] deposition. We used an air brush technique [16,19] which is a simple and quick method and allows to tune transparency easily between 0% and 100%. For that, a CNT [20] suspension in 1% sodium dodecyl sulfate (SDS, Sigma–Aldrich) in water was prepared with aid of ultrasound. The concentration was typically 1–2 mg/ml. The suspension was directly sprayed with an air brush pistol (Harder & Steenbeck, Germany) onto the substrate (Fig. 1). During the process, the substrate was kept at 100 8C on a hot plate to accelerate the drying of the fine droplets on the surface. Finally, the sample was immersed into pure water for 30 s to remove the surfactant and dried in air
0169-4332/$ – see front matter # 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2005.01.020
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M. Kaempgen et al. / Applied Surface Science 252 (2005) 425–429
Fig. 1. AFM image of a thin SWCNT network (left) and SEM image of a thick MWCNT network (right).
or on the hot plate again. UV–vis spectra were recorded in a double beam spectrometer (Perkin Elmer, Lambda 2) between 190 and 1100 nm. Measurements of surface resistivity are carried out in 4-lead configuration (Keithley 197 DMM) with pressed on contacts at room temperature. AFM was carried out on a Nanoscope IIIa (Digital Instruments, USA) and SEM on a S-800 (Hitachi, Japan). Typical images of sprayed CNT networks are shown in Fig. 1 in order to demonstrate the homogeneity at larger scales. Note, that the CNT materials used in these samples are different. Single walled CNTs (SWCNTs) are used for the left image, showing a thin network, whereas the thick network (right image) is prepared from multi walled CNTs (MWCNTs). However, the difference in density is only a result of the number of sprayed layers and not of the material used. Although no effort was put into special purification techniques, our networks look quite pure, at least on the macroscopic scale. We used the purest material available and the precursor suspension was dark but clear and free of any visible particles. From the images, it can be concluded that the network properties are dominated by the CNTs. However, contaminations from the CNT synthesis (amorphous carbon, metallic catalyst) cannot be avoided but they are small and have a very low aspect ratio compared to CNTs. These contaminations can lower the transmittance slightly but without any contribution to the conductivity because they do not percolate at this low density. The absolute thickness of the SWCNT films was determined by AFM at step edges. In Fig. 2, the correlation between transparency and thickness is
Fig. 2. Film thickness vs. transmittance plot of thin CNT networks.
presented. Due to heterogeneity on the nanometer scale the error bars of the measurement are relatively high. Although a decrease of height at higher transparency is observed, as expected, the high error bars prevent a clear standardization of our optical measurements. The results are in good agreement to data of other groups [15], further work is in progress to describe the sample properties in bulk units (e.g. V cm instead of V/sq). In order to average the poor homogeneity on the mscale, especially of thin CNT coatings (Fig. 1, left image), macroscopic substrates (quartz or plastics, 10 mm 10 mm) were used for all measurements. Transmittance and surface resistivity for both different CNT material and different coating thickness are measured at RT. Since surface resistivity changes with thickness of the coating, one has to look at the same transmittance to obtain a direct comparison. By this means, all results for various CNT coatings are summarized in a transmittance versus resistivity plot and compared to thin doped indium oxide (ITO), a standard material for transparent electrodes (Fig. 3). The results presented in Fig. 3 can be interpreted as follows: 1. It turns out that SWCNTs are more suitable for transparent conductive coatings than MWCNTs. Most likely this is due to a significantly higher diameter of each MWCNT which increases the light absorption but not the conductivity. For SWCNTs, we did not observe significant differences between different synthesis methods. The
M. Kaempgen et al. / Applied Surface Science 252 (2005) 425–429
Fig. 3. Transmittance vs. resistivity plot for sprayed CNT layers and ITO. Each curve represents different CNT material (black curves: MWCNT; grey curves: SWCNT; dark grey: ITO).
slightly better performance of laser ablated SWCNT material is probably due to longer CNTs. 2. Longer CNTs increase the conductivity for the same transparency since a decreased number of contacts exist and the electrical transport is dominated by contact resistances between the CNTs [21–23]. This effect is clearly observable for networks made of CNTs with specified length. The curves for CVD II and CVD III in Fig. 3 are from CVD MWCNTs with average lengths of 50 and 100 mm, respectively [24]. Although breaking of CNTs during the ultrasonic treatment may has taken place [25] the discussed tendency is still clearly recognizable. 3. In our samples, the conductivity comes close to that of ITO. For ITO coatings on plastic, a surface resistivity between 5 and 15 V/sq at 72% and 78% transmittance respectively was reported [26]. We found at 90% transmittance a resistivity of typically 1 kV/sq for CNT coatings. It is known that individual CNTs tolerate mechanical treatment such as bending, buckling or even certain degree of defect creation without loss of conductivity [27–29]. For macroscopic networks on flexible plastic substrates, the electrical properties also maintain under bending since the conductivity persists at the contacts between the CNTs [30]. An example is demonstrated in Fig. 4, which shows a homogeneous large area (10 cm 15 cm) CNT coating on a flexible polyester foil as substrate (left side).
427
Fig. 4. Flexible transparent coating of CNTs on a Polyester foil (left: slightly bent, right: same sample heavily crumpled). The multimeter display is to demonstrate the surface resistance in 2probe configuration (left: 1 MV, right: 12 MV).
Note that the connected multimeter is used only to demonstrate the conductivity of the sample. All values discussed here are measured afterwards in a 4-probe configuration. The CNT-coated plastic foil used in Fig. 4 shows a transmittance of about 97% and a surface resistivity of 20 kV/sq. This transparent CNT electrode works even in motion and shows long-term stability (now more than 1 year). After heavy crumpling an increase in resistivity to 70 kV/sq was observed (right side of Fig. 2). This is probably due to some abraded CNTs and bad electrical contacts since they have to cross kinks and valleys. However, it is important to note that the film is still conductive even after that heavy treatment. The performance of our films is not limited by the CNTs, but rather by the substrate. This behavior is not surprising since CNTs are known to be mechanically robust [31–33] and some CNT composites have shown a considerable toughness [34]. ITO will not show this flexibility and fail during this test (even though flexible ITO coatings on a polymer have been reported [26,35], their flexibility is very limited compared to CNT networks [36]). It is not only the simplicity of preparing such CNT coatings which makes them interesting for several applications; it is also notable that the high conductivity of ITO is not always required for transparent conductive coatings. Therefore, transparent electrodes based on CNTs have certain potential to replace ITO in at least some devices. Some applica-
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M. Kaempgen et al. / Applied Surface Science 252 (2005) 425–429
needs to combine optical and electronical experiments and the high conductivity of ITO is not absolutely required, CNT networks have a considerable potential as an alternative approach for transparent and conductive coatings.
Acknowledgements
Fig. 5. Required surface resistivity in typical applications for transparent conductive coatings compared to the performance of thin conductive CNT networks. EMI: electromagnetic interference (10 kHz–1 MHz) [37]; FPD: flat panel display (PET: polyethylene terephthalate) [38]; TS: touch screen [39]; EMS: electromagnetic shielding for cathode ray tubes [38]; ESD: electrostatic dissipation [40].
tions are already mentioned in the introduction part. In Fig. 5, we compared the resistivity of CNT coatings to target values for various applications. Thin conductive networks of CNT already fulfill the requirements for various applications. In case of electrostatic dissipation and touch screens, it is much easier to coat a surface with a conductive CNT layer than to mix a conductive composite, for example. Particularly electromagnetic shielding inside of cathode ray tubes seems to be a more promising market since the layer is protected against abrading. Cathode ray tubes are used for video display terminals and this is an important and growing application of transparent conductive layers [38]. Applications in flat panel displays seem to be reachable, particularly for coating of flexible polymers. Only shielding of electromagnetic interference (EMI) is out of reach, at least for transparent coatings. Since CNT form a thin and open network the dissipation of electromagnetic waves is not very effective. However, due to the simple manufacturing processing, making denser networks up to completely closed layers is easily possible for more effective electromagnetic shielding (Fig. 1). In conclusion, the outstanding geometrical, mechanical and electrical properties of CNTs allow the preparation of transparent and conductive coatings in large scale on nearly any substrate. Whenever one
This work is supported by the European Commision’s Sixth Framework Programme (SPANG project, contract no. NMP4-CT-2003-505483), by a grant of Fifth Framework Programme (CARDECOM Project contract no. G5RD-CT-2002-00685) and the German BMBF project (INKONAMI, FKZ: 13N8402). We thank Prof. Dr. Nicoloso (University of Darmstadt, Germany) for helpful discussions.
References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31]
H. Kataura, et al. Synth. Met. 103 (1999) 2555. O. Jost, et al. Appl. Phys. Lett. 75 (15) (1999) 2217. L. Kavan, et al. J. Phys. Chem. B 105 (2001) 10764. N. Minami, et al. Synth. Met. 116 (2001) 405. F. Hennrich, AIP Conf. Proc. 633 (2002) 619. L. Hu, et al. Nano Lett. 4 (12) (2004) 2513. N. Kouklin, et al. Appl. Phys. Lett. 85 (19) (2004) 4463. E.S. Snow, et al. J. Vac. Sci. Technol. B 22 (4) (2004) 1990. M.D. Lay, et al. Nano Lett. 4 (4) (2004) 603. M. Shirashi, et al. Chem. Phys. Lett. 394 (2004) 110. M.A. Meitl, et al. Nano Lett. 4 (9) (2004) 1643. Y. Zhou, et al. Nano Lett. 4 (10) (2004) 2031. Z. Li, et al. J. Adv. Mat. 16 (2004) 640. J. Abraham, et al. Smart Mater. Struct. 1045 (2004) 13. Z. Wu, et al. Science 305 (2004) 1273. N. Ferrer-Anglada, et al. Diam. Rel. Mater. 13 (2) (2004) 256. T. Sreekumar, et al. Chem. Mater. 15 (2003) 175. Y. Kim, et al. Jpn. J. Appl. Phys. 42 (2003) 7629. M. Kaempgen, et al. Synth. Met. 135 (2003) 755. SWCNTs (HiPco, Laser) from CNI, Houston, USA; MWCNTs from Infineon Technologies, Munich, Germany. A.B. Kaiser, et al. Phys. Rev. B 57 (1998) 3. K. Liu, et al. Prog. Nanostruct., AIP, New York, 1998, p. 61. M. Shirashi, et al. Synth. Met. 9198 (2002) 1. G. Duesberg, et al. Diam. Rel. Mater. 13 (2004) 354. K.L. Lu, et al. Carbon 34 (1996) 814. J. Herrero, et al. Vacuum 67 (2002) 611. A. Hirsch, Ang. Chem. Int. Ed. 41 (11) (2002) 1853. P.J. de Pablo, et al. Appl. Phys. Lett. 80 (8) (2002) 1462. E.D. Minot, et al., Phys. Rev. Lett. 90 (15) (2003) 156401-1. M.S. Fuhrer, et al. Physica E 6 (2000) 868. K. El-Hami, et al. Synth. Met. 132 (2003) 123.
M. Kaempgen et al. / Applied Surface Science 252 (2005) 425–429 [32] [33] [34] [35] [36]
M.R. Falvo, et al. Microsc. Microanal. 4 (1999) 504. P. Poncharat, et al. Science 283 (1999) 1513. J.G. Smith Jr., et al. Polymer 45 (2004) 825. P.E. Burrows, et al. Displays 22 (2001) 65. Y. Leterrier, et al. Thin Solid Films 460 (2004) 156.
[37] [38] [39] [40]
429
CP Films Inc., USA. (www.cpfindusprod.com). B.G. Lewis, et al. MRS Bull. (2004). Y. Matsui, et al. Mater. Res. Soc. 621 (2000) Q4.9.1. H.J. Mair, S. Roth (Eds.), Elektrisch leitende Kunststoffe, Publisher: Carl Hanser Verlag, Munich Wien, 1989p. 108.
Transparent carbon nanotube coatings M. Kaempgen a,*, G.S. Duesberg b, S. Roth a a
Max-Planck-Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany b Infineon Technologies, Corporate Research, Otto-Hahn-Ring 6, 81739 Munich, Germany
Received 5 January 2005; received in revised form 14 January 2005; accepted 16 January 2005 Available online 10 February 2005
Abstract Thin networks of carbon nanotubes (CNTs) are sprayed onto glass or plastic substrates in order to obtain conductive transparent coatings. Transparency and conductivity at room temperature of different CNT material are evaluated. CNT coatings maintain their properties under mechanical stress, even after folding the substrate. At a transparency of 90% for visible light we observe a surface resistivity of 1 kV/sq which is already a promising value for various applications. # 2005 Elsevier B.V. All rights reserved. Keywords: Carbon nanotubes; Transparent electrodes; ITO
Conductivity and high aspect ratio of carbon nanotubes (CNTs) are attractive properties for producing conductive composites with a minimum of material. This feature can be used in coatings to get transparent and conductive networks. There is an increasing interest in thin transparent networks since it has been demonstrated that they can be used for more than basic investigations [1–7]. There is also an upcoming potential for several applications such as transistors [8–11], diodes [12], sensors [13,14], optical modulators [15] or as conductive backbone for electrochemical polymer coating [16]. Since electronic and optical properties vary with CNT material, we started a comparative * Corresponding author. Tel.: +49 711 6891401; fax: +49 711 6891010. E-mail address: [email protected] (M. Kaempgen).
study on different CNT material in terms of simple conductive coatings. So far, several methods are used in order to get thin CNT networks such as filtration [7,15], drying from solvent [17], spin coating [11] or Langmuir–Blodgett [18] deposition. We used an air brush technique [16,19] which is a simple and quick method and allows to tune transparency easily between 0% and 100%. For that, a CNT [20] suspension in 1% sodium dodecyl sulfate (SDS, Sigma–Aldrich) in water was prepared with aid of ultrasound. The concentration was typically 1–2 mg/ml. The suspension was directly sprayed with an air brush pistol (Harder & Steenbeck, Germany) onto the substrate (Fig. 1). During the process, the substrate was kept at 100 8C on a hot plate to accelerate the drying of the fine droplets on the surface. Finally, the sample was immersed into pure water for 30 s to remove the surfactant and dried in air
0169-4332/$ – see front matter # 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2005.01.020
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M. Kaempgen et al. / Applied Surface Science 252 (2005) 425–429
Fig. 1. AFM image of a thin SWCNT network (left) and SEM image of a thick MWCNT network (right).
or on the hot plate again. UV–vis spectra were recorded in a double beam spectrometer (Perkin Elmer, Lambda 2) between 190 and 1100 nm. Measurements of surface resistivity are carried out in 4-lead configuration (Keithley 197 DMM) with pressed on contacts at room temperature. AFM was carried out on a Nanoscope IIIa (Digital Instruments, USA) and SEM on a S-800 (Hitachi, Japan). Typical images of sprayed CNT networks are shown in Fig. 1 in order to demonstrate the homogeneity at larger scales. Note, that the CNT materials used in these samples are different. Single walled CNTs (SWCNTs) are used for the left image, showing a thin network, whereas the thick network (right image) is prepared from multi walled CNTs (MWCNTs). However, the difference in density is only a result of the number of sprayed layers and not of the material used. Although no effort was put into special purification techniques, our networks look quite pure, at least on the macroscopic scale. We used the purest material available and the precursor suspension was dark but clear and free of any visible particles. From the images, it can be concluded that the network properties are dominated by the CNTs. However, contaminations from the CNT synthesis (amorphous carbon, metallic catalyst) cannot be avoided but they are small and have a very low aspect ratio compared to CNTs. These contaminations can lower the transmittance slightly but without any contribution to the conductivity because they do not percolate at this low density. The absolute thickness of the SWCNT films was determined by AFM at step edges. In Fig. 2, the correlation between transparency and thickness is
Fig. 2. Film thickness vs. transmittance plot of thin CNT networks.
presented. Due to heterogeneity on the nanometer scale the error bars of the measurement are relatively high. Although a decrease of height at higher transparency is observed, as expected, the high error bars prevent a clear standardization of our optical measurements. The results are in good agreement to data of other groups [15], further work is in progress to describe the sample properties in bulk units (e.g. V cm instead of V/sq). In order to average the poor homogeneity on the mscale, especially of thin CNT coatings (Fig. 1, left image), macroscopic substrates (quartz or plastics, 10 mm 10 mm) were used for all measurements. Transmittance and surface resistivity for both different CNT material and different coating thickness are measured at RT. Since surface resistivity changes with thickness of the coating, one has to look at the same transmittance to obtain a direct comparison. By this means, all results for various CNT coatings are summarized in a transmittance versus resistivity plot and compared to thin doped indium oxide (ITO), a standard material for transparent electrodes (Fig. 3). The results presented in Fig. 3 can be interpreted as follows: 1. It turns out that SWCNTs are more suitable for transparent conductive coatings than MWCNTs. Most likely this is due to a significantly higher diameter of each MWCNT which increases the light absorption but not the conductivity. For SWCNTs, we did not observe significant differences between different synthesis methods. The
M. Kaempgen et al. / Applied Surface Science 252 (2005) 425–429
Fig. 3. Transmittance vs. resistivity plot for sprayed CNT layers and ITO. Each curve represents different CNT material (black curves: MWCNT; grey curves: SWCNT; dark grey: ITO).
slightly better performance of laser ablated SWCNT material is probably due to longer CNTs. 2. Longer CNTs increase the conductivity for the same transparency since a decreased number of contacts exist and the electrical transport is dominated by contact resistances between the CNTs [21–23]. This effect is clearly observable for networks made of CNTs with specified length. The curves for CVD II and CVD III in Fig. 3 are from CVD MWCNTs with average lengths of 50 and 100 mm, respectively [24]. Although breaking of CNTs during the ultrasonic treatment may has taken place [25] the discussed tendency is still clearly recognizable. 3. In our samples, the conductivity comes close to that of ITO. For ITO coatings on plastic, a surface resistivity between 5 and 15 V/sq at 72% and 78% transmittance respectively was reported [26]. We found at 90% transmittance a resistivity of typically 1 kV/sq for CNT coatings. It is known that individual CNTs tolerate mechanical treatment such as bending, buckling or even certain degree of defect creation without loss of conductivity [27–29]. For macroscopic networks on flexible plastic substrates, the electrical properties also maintain under bending since the conductivity persists at the contacts between the CNTs [30]. An example is demonstrated in Fig. 4, which shows a homogeneous large area (10 cm 15 cm) CNT coating on a flexible polyester foil as substrate (left side).
427
Fig. 4. Flexible transparent coating of CNTs on a Polyester foil (left: slightly bent, right: same sample heavily crumpled). The multimeter display is to demonstrate the surface resistance in 2probe configuration (left: 1 MV, right: 12 MV).
Note that the connected multimeter is used only to demonstrate the conductivity of the sample. All values discussed here are measured afterwards in a 4-probe configuration. The CNT-coated plastic foil used in Fig. 4 shows a transmittance of about 97% and a surface resistivity of 20 kV/sq. This transparent CNT electrode works even in motion and shows long-term stability (now more than 1 year). After heavy crumpling an increase in resistivity to 70 kV/sq was observed (right side of Fig. 2). This is probably due to some abraded CNTs and bad electrical contacts since they have to cross kinks and valleys. However, it is important to note that the film is still conductive even after that heavy treatment. The performance of our films is not limited by the CNTs, but rather by the substrate. This behavior is not surprising since CNTs are known to be mechanically robust [31–33] and some CNT composites have shown a considerable toughness [34]. ITO will not show this flexibility and fail during this test (even though flexible ITO coatings on a polymer have been reported [26,35], their flexibility is very limited compared to CNT networks [36]). It is not only the simplicity of preparing such CNT coatings which makes them interesting for several applications; it is also notable that the high conductivity of ITO is not always required for transparent conductive coatings. Therefore, transparent electrodes based on CNTs have certain potential to replace ITO in at least some devices. Some applica-
428
M. Kaempgen et al. / Applied Surface Science 252 (2005) 425–429
needs to combine optical and electronical experiments and the high conductivity of ITO is not absolutely required, CNT networks have a considerable potential as an alternative approach for transparent and conductive coatings.
Acknowledgements
Fig. 5. Required surface resistivity in typical applications for transparent conductive coatings compared to the performance of thin conductive CNT networks. EMI: electromagnetic interference (10 kHz–1 MHz) [37]; FPD: flat panel display (PET: polyethylene terephthalate) [38]; TS: touch screen [39]; EMS: electromagnetic shielding for cathode ray tubes [38]; ESD: electrostatic dissipation [40].
tions are already mentioned in the introduction part. In Fig. 5, we compared the resistivity of CNT coatings to target values for various applications. Thin conductive networks of CNT already fulfill the requirements for various applications. In case of electrostatic dissipation and touch screens, it is much easier to coat a surface with a conductive CNT layer than to mix a conductive composite, for example. Particularly electromagnetic shielding inside of cathode ray tubes seems to be a more promising market since the layer is protected against abrading. Cathode ray tubes are used for video display terminals and this is an important and growing application of transparent conductive layers [38]. Applications in flat panel displays seem to be reachable, particularly for coating of flexible polymers. Only shielding of electromagnetic interference (EMI) is out of reach, at least for transparent coatings. Since CNT form a thin and open network the dissipation of electromagnetic waves is not very effective. However, due to the simple manufacturing processing, making denser networks up to completely closed layers is easily possible for more effective electromagnetic shielding (Fig. 1). In conclusion, the outstanding geometrical, mechanical and electrical properties of CNTs allow the preparation of transparent and conductive coatings in large scale on nearly any substrate. Whenever one
This work is supported by the European Commision’s Sixth Framework Programme (SPANG project, contract no. NMP4-CT-2003-505483), by a grant of Fifth Framework Programme (CARDECOM Project contract no. G5RD-CT-2002-00685) and the German BMBF project (INKONAMI, FKZ: 13N8402). We thank Prof. Dr. Nicoloso (University of Darmstadt, Germany) for helpful discussions.
References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31]
H. Kataura, et al. Synth. Met. 103 (1999) 2555. O. Jost, et al. Appl. Phys. Lett. 75 (15) (1999) 2217. L. Kavan, et al. J. Phys. Chem. B 105 (2001) 10764. N. Minami, et al. Synth. Met. 116 (2001) 405. F. Hennrich, AIP Conf. Proc. 633 (2002) 619. L. Hu, et al. Nano Lett. 4 (12) (2004) 2513. N. Kouklin, et al. Appl. Phys. Lett. 85 (19) (2004) 4463. E.S. Snow, et al. J. Vac. Sci. Technol. B 22 (4) (2004) 1990. M.D. Lay, et al. Nano Lett. 4 (4) (2004) 603. M. Shirashi, et al. Chem. Phys. Lett. 394 (2004) 110. M.A. Meitl, et al. Nano Lett. 4 (9) (2004) 1643. Y. Zhou, et al. Nano Lett. 4 (10) (2004) 2031. Z. Li, et al. J. Adv. Mat. 16 (2004) 640. J. Abraham, et al. Smart Mater. Struct. 1045 (2004) 13. Z. Wu, et al. Science 305 (2004) 1273. N. Ferrer-Anglada, et al. Diam. Rel. Mater. 13 (2) (2004) 256. T. Sreekumar, et al. Chem. Mater. 15 (2003) 175. Y. Kim, et al. Jpn. J. Appl. Phys. 42 (2003) 7629. M. Kaempgen, et al. Synth. Met. 135 (2003) 755. SWCNTs (HiPco, Laser) from CNI, Houston, USA; MWCNTs from Infineon Technologies, Munich, Germany. A.B. Kaiser, et al. Phys. Rev. B 57 (1998) 3. K. Liu, et al. Prog. Nanostruct., AIP, New York, 1998, p. 61. M. Shirashi, et al. Synth. Met. 9198 (2002) 1. G. Duesberg, et al. Diam. Rel. Mater. 13 (2004) 354. K.L. Lu, et al. Carbon 34 (1996) 814. J. Herrero, et al. Vacuum 67 (2002) 611. A. Hirsch, Ang. Chem. Int. Ed. 41 (11) (2002) 1853. P.J. de Pablo, et al. Appl. Phys. Lett. 80 (8) (2002) 1462. E.D. Minot, et al., Phys. Rev. Lett. 90 (15) (2003) 156401-1. M.S. Fuhrer, et al. Physica E 6 (2000) 868. K. El-Hami, et al. Synth. Met. 132 (2003) 123.
M. Kaempgen et al. / Applied Surface Science 252 (2005) 425–429 [32] [33] [34] [35] [36]
M.R. Falvo, et al. Microsc. Microanal. 4 (1999) 504. P. Poncharat, et al. Science 283 (1999) 1513. J.G. Smith Jr., et al. Polymer 45 (2004) 825. P.E. Burrows, et al. Displays 22 (2001) 65. Y. Leterrier, et al. Thin Solid Films 460 (2004) 156.
[37] [38] [39] [40]
429
CP Films Inc., USA. (www.cpfindusprod.com). B.G. Lewis, et al. MRS Bull. (2004). Y. Matsui, et al. Mater. Res. Soc. 621 (2000) Q4.9.1. H.J. Mair, S. Roth (Eds.), Elektrisch leitende Kunststoffe, Publisher: Carl Hanser Verlag, Munich Wien, 1989p. 108.