Electrical transport properties of small diameter single-walled carbon nanotubes aligned on ST-cut quartz substrates
© Watanabe et al.; licensee Springer. 2014
Received: 8 May 2014
Accepted: 19 July 2014
Published: 31 July 2014
A method is introduced to isolate and measure the electrical transport properties of individual single-walled carbon nanotubes (SWNTs) aligned on an ST-cut quartz, from room temperature down to 2 K. The diameter and chirality of the measured SWNTs are accurately defined from Raman spectroscopy and atomic force microscopy (AFM). A significant up-shift in the G-band of the resonance Raman spectra of the SWNTs is observed, which increases with increasing SWNTs diameter, and indicates a strong interaction with the quartz substrate. A semiconducting SWNT, with diameter 0.84 nm, shows Tomonaga-Luttinger liquid and Coulomb blockade behaviors at low temperatures. Another semiconducting SWNT, with a thinner diameter of 0.68 nm, exhibits a transition from the semiconducting state to an insulating state at low temperatures. These results elucidate some of the electrical properties of SWNTs in this unique configuration and help pave the way towards prospective device applications.
Single-walled carbon nanotubes (SWNTs), with their miniature size, low structural defects, and various other superior properties [1–4], are very attractive nanomaterials as basis for future electronic devices [5–7]. However, there are still many technical obstacles towards the realization of SWNT-based devices, such as the difficulty of their positioning on a substrate, as well as the lack of control of their chirality, which eventually defines their electronic properties. Furthermore, synthesized SWNTs by chemical vapor deposition (CVD) on a substrate are usually short (around 10 μm) and randomly dispersed, which makes it difficult for device fabrication. Recently, it has been reported that arrays of long (hundreds of microns) and horizontally highly aligned SWNTs could be synthesized on some single crystal substrates, such as ST-cut quartz  and sapphire . This is an important breakthrough, as the length of the synthesized SWNTs, and their high alignment, makes their electrical characterization and device fabrication much more accessible than ever before. Indeed, a field-effect transistor (FET) has been demonstrated using aligned SWNT arrays on an ST-cut quartz substrate . It is also noted that the latest Raman and photoluminescence data suggest that these SWNTs have predominantly semiconducting properties [10, 11]. However, and despite a lot of research work on SWNT array on ST-cut quartz [10, 12, 13], no data has been reported so far on the electrical properties or device fabrication of a single isolated SWNT on these substrates, except after their transfer onto silicon substrates . We believe that this is important in order to understand the underlying physics of the SWNTs in this unique configuration, which is crucial for any prospective device applications. Furthermore, it has been reported recently that the aligned SWNTs on ST-cut quartz substrates are in strong interaction with the substrate [14, 15], and the understanding of this interaction and its effects on the electrical transport properties of the SWNTs is therefore very important.
The lack of published data on an individual SWNT could be attributed to the technical difficulty in applying standard electron-beam lithography method for the fabrication of electrical terminals on an individual SWNT on these substrates, as it is usually inseparable from the other SWNTs in the arrays.
In this letter, we present a method for the fabrication of electrical terminals on individual SWNTs aligned on an ST-quartz substrate and the measurement of their electrical transport properties from room temperature down to 2 K. The method consists of CVD synthesis of an individual SWNT from evaporated metal catalyst pad and shadow mask evaporation of metallic electrical contacts on the SWNT. The thickness and dimensions of the catalyst pad are optimized to yield on average one long and horizontally aligned single SWNT after CVD synthesis. In contrast to standard electron-beam lithography technique, this method has the advantage of not exposing the SWNTs to any electron beam irradiation or chemicals that are reported to damage or/and contaminate the SWNTs [16, 17]. Furthermore, in order to minimize any damage or contamination of the SWNT before electrical properties measurements, scanning electron microscopy (SEM), Raman spectroscopy mapping, and atomic force microscopy (AFM) are performed only after all the electrical transport measurements are achieved. The electrical properties of individual SWNTs are measured using four-terminal method to minimize the effects of the contact resistance from the electrodes [18, 19]. The results are compared with theory and discussed in connection with the strong interaction with the substrate.
Electrodes on the SWNT are also fabricated using shadow mask evaporation technique. The metal masks are prepared by the same method as of that used for catalyst pattern. Palladium (Pd) is selected as the material of the electrodes because of its low contact resistance to SWNTs [20, 21]. The Pd electrodes, with a thickness of 50 nm, are EB evaporated in a four-terminal configuration, with a typical distance of 4.0 μm between adjacent electrodes. The electrical properties of the SWNTs are measured from room temperature down to 2 K, using a physical properties measurement system (PPMS, Quantum Design Inc., San Diego, CA, USA) for the temperature control. Voltages of approximately ±1 V are applied by a voltage source (33220A, Agilent, Santa Clara, MA, USA) through a 10 MΩ resistance connected in series with the sample, and the voltage is measured across the inner electrodes on the sample by a voltmeter (Model 2000 Multimeter, Keithley, Cleveland, OH, USA).
For imaging and analytical characterization of SWNTs under the terminals, Raman spectral mapping (RAMAN-11, Nanophoton Corp., Osaka, Japan), AFM system (Nanocute, SII NanoTechnology Inc.), and SEM system (SMI9800SE, SII NanoTechnology Inc.) are used. Raman spectroscopy is performed with a laser of 532 nm in wavelength and spot size of 0.5 μm. AFM is conducted in cyclic contact AC mode.
Results and discussion
First, the values of the resistance at room temperature are considered. The intrinsic resistance of a SWNT in the diffusive regime (non-ballistic) can be estimated from the formula R = R c + R Q (L/l + 1), where R c , R Q = h/4e2 ~ 6.45 kΩ, L, and l are the contact resistance between SWNT and the electrodes, the quantum resistance of a SWNT, the measured length of the SWNT, and the electron's mean free path, respectively . By comparing the 2 and 4-terminal resistances of our samples, and using L = 4 μm (distance between the inner voltage terminals), R c and l are estimated to be 8 and 19 kΩ, and 148 and 18 nm, for SWNT1 and SWNT2, respectively. The deduced mean free paths for SWNT1 and SWNT2 at 300 K are within the range of reported values for SWNTs [18, 33, 34]. Nevertheless, it is very difficult to compare directly with our samples because most of the published electrical transport properties data either do not define the chirality of the measured SWNTs or it is about SWNTs with larger diameters than ours. In general, the SWNT's resistance at high temperatures is theoretically attributed to inelastic scattering between electrons and acoustic phonons within the SWNT . However, the experimentally measured mean free paths of our SWNTs and others [18, 33, 34] are smaller by an order of magnitude than the theoretical calculations . Recently, this discrepancy has been successfully addressed by introducing the effect of surface polar phonons (SPPs) from the substrate [36, 37]. We speculate here that due to its narrower diameter, SWNT2 might be more susceptible to SPPs from the substrate, which enhance its room temperature resistance (i.e., shorter l) in comparison with SWNT1. It is noted from our results that the mechanisms defining the shift in the G-band and the electron's mean free path l should be uncorrelated; otherwise, we would expect SWNT1 to have a shorter l. This is indeed in support of an extrinsic contribution of SPPs from the substrate than an intrinsic one from the SWNTs' own phonons. Further detailed studies on both contributions are therefore needed in the future.
Since SWNT1 is a semiconductor, the measured decrease of its resistance from room temperature down to about 120 K cannot be attributed to an intrinsic metallic property . Based on the observed strong effect of the substrate on the G-band of SWNT1, we speculate that this metallic-like behavior could be originating from an interaction with the substrate that dominates at high temperature. Indeed, the expected semiconducting behavior of the resistance versus temperature is gradually recovered below around 120 K (Figure 4a). One possible indication for a semiconducting energy gap is a thermal activation dependence of the resistance versus temperature, i.e., in the form R ~ exp(U/kBT), where U and kB are an energy barrier and Boltzmann constant, respectively . In order to explore this behavior, a plot of Ln(R) versus 1/T is shown in Figure 4c, which could be very well fitted to the above activation formula from 60 K down to 5 K, with U ~ 0.6 meV. Assuming a standard semiconductor theory , this leads to a semiconducting energy gap of E g = 2U = 1.2 meV. This value is about 2 orders of magnitude smaller than the expected and directly measured energy gap of 1.11 eV for SWNT1 . This difference is not surprising as the simple activation formula above is used just as a qualitative guide, and the resistance versus temperature dependence of semiconducting SWNTs is very complex and there is no simple explicit formula in relation with E g . A more accurate technique of extracting E g is from voltage-current measurements with a gating voltage . However, this is not possible in our current experimental setup.
The resistance of sample SWNT2 increases with decreasing temperature down to 2 K. In order to explore any thermal activation behavior, Figure 4d shows a plot of Ln(R) versus 1/T. The data from room temperature down to 20 K can be fitted very well with the activation formula, leading to an energy gap of E g = 2U = 22 meV. This is in qualitative agreement with a semiconducting behavior in general but not quantitatively with E g = 1.42 eV for SWNT2 , which is due to the same reasons explained before. It is noted that SWNT2 does not exhibit any decrease of R with decreasing T as observed for SWNT1. This could be due to a weaker effect from the substrate (less up-shift in G-band) than that of SWNT1 because of possibly the larger E g of SWNT2.
Finally, the appearance of completely different properties for SWNT1 (TLL/CB) and SWNT2 (transition to an insulating state) at low temperatures and their relation with the observed strong interaction with the quartz substrate is currently not understood. Further theoretical and experimental efforts are underway to elucidate these effects.
In conclusion, a method is introduced to isolate and measure the electrical properties of individual SWNTs aligned on an ST-cut quartz substrate, from room temperature down to 2 K. The diameter and chirality of the measured SWNTs are accurately defined from resonant Raman spectroscopy and AFM. A significant up-shift in the G-band of the Raman spectra of the SWNTs is observed, which increases with increasing SWNTs diameter and indicates a strong interaction with the quartz substrate. A semiconducting SWNT (diameter 0.84 nm) shows Tomonaga-Luttinger liquid and Coulomb blockade behaviors at low temperatures. Another semiconducting SWNT (diameter of 0.68 nm) exhibits a transition from the semiconducting state to an insulating state at low temperatures. These results elucidate some of the electrical transport properties of SWNTs on ST-cut quartz substrates, which can be useful for prospective device applications.
This study was supported by Nano-Integration Foundry (NIMS) in ‘Nanotechnology Platform Project’ operated by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. ESS would like to acknowledge the support and hospitality of NIMS during his visit as a Guest Researcher.
- Tans SJ, Verschueren ARM, Dekker C: Room-temperature transistor based on a single carbon nanotube. Nature 1998, 393: 49–52.View ArticleGoogle Scholar
- Durkop T, Getty SA, Cobas E, Fuhrer MS: Extraordinary mobility in semiconducting carbon nanotubes. Nano Lett 2004, 4: 35–39.View ArticleGoogle Scholar
- Walters DA, Ericson LM, Casavant MJ, Liu J, Colbert DT, Smith KA, Smalley RE: Elastic strain of freely suspended single-wall carbon nanotube ropes. Appl Phys Lett 1999, 74: 3803–3805.View ArticleGoogle Scholar
- Yu MF, Files BS, Arepalli S, Ruoff RS: Tensile loading of ropes of single wall carbon nanotubes and their mechanical properties. Phys Rev Lett 2000, 84: 5552–5555.View ArticleGoogle Scholar
- Hong S, Myung S: Nanotube electronics - a flexible approach to mobility. Nat Nanotechnol 2007, 2: 207–208.View ArticleGoogle Scholar
- Cao Q, Han SJ: Single-walled carbon nanotubes for high-performance electronics. Nanoscale 2013, 5: 8852–8863.View ArticleGoogle Scholar
- Franklin AD, Chen ZH: Length scaling of carbon nanotube transistors. Nat Nanotechnol 2010, 5: 858–862.View ArticleGoogle Scholar
- Kang SJ, Kocabas C, Ozel T, Shim M, Pimparkar N, Alam MA, Rotkin SV, Rogers JA: High-performance electronics using dense, perfectly aligned arrays of single-walled carbon nanotubes. Nat Nanotechnol 2007, 2: 230–236.View ArticleGoogle Scholar
- Ago H, Nakamura K, Ikeda K, Uehara N, Ishigami N, Tsuji M: Aligned growth of isolated single-walled carbon nanotubes programmed by atomic arrangement of substrate surface. Chem Phys Lett 2005, 408: 433–438.View ArticleGoogle Scholar
- Ding L, Tselev A, Wang JY, Yuan DN, Chu HB, McNicholas TP, Li Y, Liu J: Selective growth of well-aligned semiconducting single-walled carbon nanotubes. Nano Lett 2009, 9: 800–805.View ArticleGoogle Scholar
- Ishigami N, Ago H, Imamoto K, Tsuji M, Iakoubovskii K, Minami N: Crystal plane dependent growth of aligned single-walled carbon nanotubes on sapphire. J Am Chem Soc 2008, 130: 9918–9924.View ArticleGoogle Scholar
- Yuan DN, Ding L, Chu HB, Feng YY, McNicholas TP, Liu J: Horizontally aligned single-walled carbon nanotube on quartz from a large variety of metal catalysts. Nano Lett 2008, 8: 2576–2579.View ArticleGoogle Scholar
- Liu BL, Wang C, Liu J, Che YC, Zhou CW: Aligned carbon nanotubes: from controlled synthesis to electronic applications. Nanoscale 2013, 5: 9483–9502.View ArticleGoogle Scholar
- Ding L, Zhou W, McNicholas TP, Wang J, Chu H, Li Y, Liu J: Direct observation of the strong interaction between carbon nanotubes and quartz substrate. Nano Res 2009, 2: 903–910.View ArticleGoogle Scholar
- Ozel T, Abdula D, Hwang E, Shim M: Nonuniform compressive strain in horizontally aligned single-walled carbon nanotubes grown on single crystal quartz. ACS Nano 2009, 3: 2217–2224.View ArticleGoogle Scholar
- Khamis SM, Jones RA, Johnson ATC: Optimized photolithographic fabrication process for carbon nanotube devices. AIP Adv 2011, 1: 022106.View ArticleGoogle Scholar
- Smith BW, Luzzi DE: Electron irradiation effects in single wall carbon nanotubes. J Appl Phys 2001, 90: 3509–3515.View ArticleGoogle Scholar
- Gao B, Chen YF, Fuhrer MS, Glattli DC, Bachtold A: Four-point resistance of individual single-wall carbon nanotubes. Phys Rev Lett 2005, 95: 196802.View ArticleGoogle Scholar
- Makarovski A, Zhukov A, Liu J, Finkelstein G: Four-probe measurements of carbon nanotubes with narrow metal contacts. Phys Rev B 2007, 76: 161405.View ArticleGoogle Scholar
- Javey A, Guo J, Wang Q, Lundstrom M, Dai HJ: Ballistic carbon nanotube field-effect transistors. Nature 2003, 424: 654–657.View ArticleGoogle Scholar
- Nosho Y, Ohno Y, Kishimoto S, Mizutani T: Relation between conduction property and work function of contact metal in carbon nanotube field-effect transistors. Nanotechnol 2006, 17: 3412–3415.View ArticleGoogle Scholar
- Saito R, Hofmann M, Dresselhaus G, Jorio A, Dresselhaus MS: Raman spectroscopy of graphene and carbon nanotubes. Adv Phys 2011, 60: 413–550.View ArticleGoogle Scholar
- Weisman RB, Bachilo SM: Dependence of optical transition energies on structure for single-walled carbon nanotubes in aqueous suspension: an empirical Kataura plot. Nano Lett 2003, 3: 1235–1238.View ArticleGoogle Scholar
- Zhang YY, Zhang J, Son HB, Kong J, Liu ZF: Substrate-induced Raman frequency variation for single-walled carbon nanotubes. J Am Chem Soc 2005, 127: 17156–17157.View ArticleGoogle Scholar
- Jorio A, Souza AG, Dresselhaus G, Dresselhaus MS, Swan AK, Unlu MS, Goldberg BB, Pimenta MA, Hafner JH, Lieber CM, Saito R: G-band resonant Raman study of 62 isolated single-wall carbon nanotubes. Phys Rev B 2002, 65: 155412.View ArticleGoogle Scholar
- Xiao JL, Dunham S, Liu P, Zhang YW, Kocabas C, Moh L, Huang YG, Hwang KC, Lu C, Huang W, Rogers JA: Alignment controlled growth of single-walled carbon nanotubes on quartz substrates. Nano Lett 2009, 9: 4311–4319.View ArticleGoogle Scholar
- Rutkowska A, Walker D, Gorfman S, Thomas PA, Macpherson JV: Horizontal alignment of chemical vapor-deposited SWNTs on single-crystal quartz surfaces: further evidence for epitaxial alignment. J Phys Chem C 2009, 113: 17087–17096.View ArticleGoogle Scholar
- Cronin SB, Swan AK, Unlu MS, Goldberg BB, Dresselhaus MS, Tinkham M: Measuring the uniaxial strain of individual single-wall carbon nanotubes: resonance Raman spectra of atomic-force-microscope modified single-wall nanotubes. Phys Rev Lett 2004, 93: 167401.View ArticleGoogle Scholar
- Yang W, Wang RZ, Yan H: Strain-induced Raman-mode shift in single-wall carbon nanotubes: calculation of force constants from molecular-dynamics simulations. Phys Rev B 2008, 77: 195440.View ArticleGoogle Scholar
- Gao B, Jiang L, Ling X, Zhang J, Liu ZF: Chirality-dependent Raman frequency variation of single-walled carbon nanotubes under uniaxial strain. J Phys Chem C 2008, 112: 20123–20125.View ArticleGoogle Scholar
- Li LL, Chang TC, Li GQ: Strain dependent G-band mode frequency of single-walled carbon nanotubes. Carbon 2011, 49: 4412–4419.View ArticleGoogle Scholar
- Datta S: Quantum Transport: Atom to Transistor. Cambridge: Cambridge University Press; 2005.View ArticleGoogle Scholar
- Purewal MS, Hong BH, Ravi A, Chandra B, Hone J, Kim P: Scaling of resistance and electron mean free path of single-walled carbon nanotubes. Phys Rev Lett 2007, 98: 186808.View ArticleGoogle Scholar
- Sundqvist P, Garcia-Vidal FJ, Flores F, Moreno-Moreno M, Gomez-Navarro C, Bunch JS, Gomez-Herrero J: Voltage and length-dependent phase diagram of the electronic transport in carbon nanotubes. Nano Lett 2007, 7: 2568–2573.View ArticleGoogle Scholar
- Perebeinos V, Tersoff J, Avouris P: Electron–phonon interaction and transport in semiconducting carbon nanotubes. Phys Rev Lett 2005, 94: 086802.View ArticleGoogle Scholar
- Chandra B, Perebeinos V, Berciaud S, Katoch J, Ishigami M, Kim P, Heinz TF, Hone J: Low bias electron scattering in structure-identified single wall carbon nanotubes: role of substrate polar phonons. Phys Rev Lett 2011, 107: 146601.View ArticleGoogle Scholar
- Perebeinos V, Rotkin SV, Petrov AG, Avouris P: The effects of substrate phonon mode scattering on transport in carbon nanotubes. Nano Lett 2009, 9: 312–316.View ArticleGoogle Scholar
- Kane CL, Mele EJ, Lee RS, Fischer JE, Petit P, Dai H, Thess A, Smalley RE, Verschueren ARM, Tans SJ, Dekker C: Temperature-dependent resistivity of single-wall carbon nanotubes. Europhys Lett 1998, 41: 683–688.View ArticleGoogle Scholar
- Kittel C: Introduction to Solid State Physics. New York: Wiley; 2004.Google Scholar
- Wong HSP, Akinwande D: Carbon Nanotube and Graphene Device Physics. Cambridge: Cambridge University Press; 2011.Google Scholar
- Bockrath M, Cobden DH, Lu J, Rinzler AG, Smalley RE, Balents L, McEuen PL: Luttinger-liquid behaviour in carbon nanotubes. Nature 1999, 397: 598–601.View ArticleGoogle Scholar
- Ishii H, Kataura H, Shiozawa H, Yoshioka H, Otsubo H, Takayama Y, Miyahara T, Suzuki S, Achiba Y, Nakatake M, Narimura T, Higashiguchi M, Shimada K, Namatame H, Taniguchi M: Direct observation of Tomonaga-Luttinger-liquid state in carbon nanotubes at low temperatures. Nature 2003, 426: 540–544.View ArticleGoogle Scholar
- Danilchenko BA, Shpinar LI, Tripachko NA, Voitsihovska EA, Zelensky SE, Sundqvist B: High temperature Luttinger liquid conductivity in carbon nanotube bundles. Appl Phys Lett 2010, 97: 072106.View ArticleGoogle Scholar
- Bockrath M, Cobden DH, McEuen PL, Chopra NG, Zettl A, Thess A, Smalley RE: Single-electron transport in ropes of carbon nanotubes. Science 1997, 275: 1922–1925.View ArticleGoogle Scholar
- Dayen JF, Wade TL, Rizza G, Golubev DS, Cojocaru CS, Pribat D, Jehl X, Sanquer M, Wegrowe JE: Conductance of disordered semiconducting nanowires and carbon nanotubes: a chain of quantum dots. Eur Physical J Appl Physics 2009, 48: 10604.View ArticleGoogle Scholar
- Kane C, Balents L, Fisher MPA: Coulomb interactions and mesoscopic effects in carbon nanotubes. Phys Rev Lett 1997, 79: 5086–5089.View ArticleGoogle Scholar
- Postma HWC, Teepen T, Yao Z, Grifoni M, Dekker C: Carbon nanotube single-electron transistors at room temperature. Science 2001, 293: 76–79.View ArticleGoogle Scholar
- Reich S, Thomsen C, Maultzsch J: Carbon Nanotubes: Basic Concepts and Physical Properties. Wiley-VCH: Weinheim; 2004.Google Scholar
- Bellucci S, Gonzalez J, Onorato P: Crossover from the Luttinger-liquid to Coulomb-blockade regime in carbon nanotubes. Phys Rev Lett 2005, 95: 186403.View ArticleGoogle Scholar
- Zhou CW, Kong J, Dai HJ: Electrical measurements of individual semiconducting single-walled carbon nanotubes of various diameters. Appl Phys Lett 2000, 76: 1597–1599.View ArticleGoogle Scholar
- Deshpande VV, Chandra B, Caldwell R, Novikov DS, Hone J, Bockrath M: Mott insulating state in ultraclean carbon nanotubes. Science 2009, 323: 106–110.View ArticleGoogle Scholar
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