Catalyst-Free Growth of Nanocrystalline Graphene/Graphite Patterns from Photoresist

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Catalyst-free growth of nanocrystalline graphene/graphite patterns from photoresist

ARTICLE in CHEMICAL COMMUNICATIONS · MARCH 2013 Impact Factor: 6.83 · DOI: 10.1039/c3cc00089c · Source: PubMed

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Catalyst-free growth of nanocrystalline graphene/

Cite this: Chem. Commun., 2013, graphite patterns from photoresist† 49, 2789 Zengxing Zhang,*ab Binghui Ge,c Yunxian Guo,a Dongsheng Tang,d Received 5th January 2013, Xiaojuan Wanga and Fengli Wangb Accepted 19th February 2013

DOI: 10.1039/c3cc00089c www.rsc.org/chemcomm

Catalyst-free growth of a nanocrystalline few-layer graphene patterns with different thicknesses can be easily and accurately (or graphite) film from photoresist on variable substrates was defined and assembled. The easy approach to make graphene/ demonstrated. The thickness of the film can be easily controlled graphite patterns should be helpful for designing pure carbon from 1 nm to hundreds of nanometers. With this method, devices, such as electronics, transparent electrodes and graphene/graphite patterns with different thicknesses have been chemical or biosensors.18,19 designed for integrated electronics. The catalyst-free growth of nanocrystalline few-layer graphene (or graphite) film from photoresist is schematically Graphene is a single layer of carbon atoms with a honeycomb demonstrated in Fig. 1A. The source photoresist used here is structure.1 It has attracted great attention due to its unique RZJ-304 or S-1813. Both of them are positive. In a typical structure and excellent electrical, mechanical and thermal procedure, the photoresist is firstly spin-coated on SiO2/Si properties.2–7 Among these studies, growth of graphene is substrates and baked at 110 1C for 2 minutes, it is then very important as it is the foundation for further studies and annealed in a horizontal quartz tube under vacuum and applications. Graphene can be obtained by mechanical peeling- protection of 100 SCCM 5% H2/Ar gas flow. A large-area film off,1 chemical exfoliation,8,9 annealing SiC10 or chemical vapor can be formed on the substrates at a temperature of 1000 1C. deposition (CVD)11–13 methods. From these methods, CVD We also found that the products can be produced on variable seems to be the most promising way to produce large-area substrates in this way. Besides SiO2/Si substrates, we have 14,15 graphene at low cost. However, in this procedure, graphene tried quartz, Si, Cu film, Al2O3 ceramic, and so on. The is often grown on a metal film catalyst and needs to be samples produced on these substrates all have similar X-ray transferred. The inevitable transfer process often results in breaks, wrinkles, chemical pollutions and increasing the cost. It is thus very valuable to develop a catalyst-free method to directly grow graphene on substrate.16–18 Here, we demonstrate a simple approach to directly grow large-area nanocrystalline few-layer graphene (or graphite) films from photoresist on variable substrates without catalyst. Their thickness can be controlled easily from 1 nm to hundreds of nanometers. Due to the well-known properties of photoresist, graphene/graphite

a Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, School of Physics Science and Engineering, Tongji University, Shanghai 200092, China. E-mail: [email protected] b MOE Key Laboratory of Advanced Micro-structured Materials, School of Physics Fig. 1 (A) Schematic growth process of a few-layer nanographene film from

Science and Engineering, Tongji University, Shanghai 200092, China photoresist on SiO2/Si substrate. (B) The thickness dependent curve of nano- c Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, crystalline few-layer graphene (or graphite) on photoresist. (C) An AFM image of Chinese Academy of Sciences, Beijing 100190, China carbon layers with the thickness of 1 nm from photoresist with the thickness of d College of Physics and Information Science, Hunan Normal University, 10 nm. (D) Optical microscope image of a nanocrystalline graphene/graphite

Changsha 410081, China pattern of diﬀerent thicknesses on SiO2/Si substrate to form a sketch of the † Electronic supplementary information (ESI) available. See DOI: 10.1039/ graphene honeycomb lattice. The thickness of the schematic carbon atoms is c3cc00089c 180 nm, the bonds, 70 nm and the background area, 1.5 nm.

This journal is c The Royal Society of Chemistry 2013 Chem. Commun., 2013, 49, 2789--2791 2789 Communication ChemComm photoelectron spectroscopy (XPS) and Raman spectroscopy to see in Fig. 2C that the atomic structure is a hexagonal spectra (see Fig. S1 and S2 in ESI†). honeycomb. It should be noted here that the SAED pattern The thickness of the produced film can be controlled easily. includes two sets of hexagonal spots, which means that there In our experiment, we found that the thickness of the produced should be two pieces of crystalline graphene overlapped in the samples is mostly linearly dependent on that of the source examined area. Considering that it is difficult to find large-area photoresist, which grows at around 1/10 after annealing at uniform HRTEM images of graphene, it could be decided 1000 1C (Fig. 1B). Through controllably varying the thickness that the obtained film is mainly composed of nanocrystalline of the photoresist, the products can be obtained from around graphene of tens of nanometers, which is consistent to the 1 nm to hundreds of nanometers easily. In order to get an results of Raman spectroscopy in the ESI.† ultrathin film around 1 nm, the as-received RZJ-304 photoresist Fig. S2 (ESI†) shows the Raman spectroscopy results of the needs to be diluted to 1/100 by propylene glycol monomethyl samples on different substrates. The results exhibit similar ether acetate (PMA) and spin-coated on substrates at 7000 rpm features with a strong D band and a G band, indicating that for 1 minute so as to obtain about 10 nm-thick photoresist. The the samples on different substrates have a similar crystal surface profile of the as-produced film from B10 nm-thick structure. The D band originates from the in-plane defects photoresist on SiO2/Si substrates was examined with atomic and edge effect in the graphene. There is almost no D band force microscopy (AFM) and a typical AFM image is shown in in the perfect large-area graphene. With the size decreasing, the Fig. 1C. The thickness of the film is around 1 nm, which is D band starts to appear due to the edge effect.20,21 And it almost similar to that of monolayer graphene. becomes strong when the size decreases to nanoscale.17,22,23 As we all know, photoresist is sensitive to specific light and The formation of the nanocrystalline few-layer graphene can can be accurately defined for certain patterns. Thus, by our be understood easily. A similar growth process has often been discovered approach, graphene/graphite structures with differ- used to grow carbon fibres.24 The source material of photoresist ent thicknesses can be easily produced just by patterning mainly includes aromatic molecules. These aromatic molecules different thicknesses of photoresist and annealing at 1000 1C can be carbonized and graphitized at high temperature. Based (Fig. 1D). Fig. 1D also exhibits that the product is uniform on on the experimental results of the growth of carbon fibres, the large scale. Beyond the above, we also found that nanocrystal- aromatic molecules start to graphitize at around 1000 1C. This line few-layer graphene film can be produced in a CVD way should be the reason that we can get nanocrystalline few-layer instead of the above-mentioned in situ annealing. While we graphene. Furthermore, it should be noted here that it is annealed the substrates partially covered by photoresist, an possible to get high quality graphene if a higher temperature ultrathin carbon film of around 1.5 nm can be obtained on the is used to anneal the samples, e.g. a temperature above 2000 1C. clean substrates near the photoresist within 1 cm (see Methods The electrical properties of graphene or graphite are strongly and Fig. S3d in ESI†). This is due to a small quantity of dependent on their thickness. We measured the sheet resis- photoresist molecules being vaporized from the photoresist tance of the as-produced samples with a four-point probe and transported onto the contiguous substrates to form nano- method. The results exhibit that the sheet resistance value of graphene during the growing process. the nanographene of around 1 nm is about 30 KO &À1. It is one The crystal structure of the products was examined with order higher than typical CVD-derived graphene because the transmission electron microscopy (TEM) and the results are samples are mainly nanocrystalline graphene.19 When the displayed in Fig. 2A–C. Fig. 2A–C are the results of a sample thickness increases to 180 nm, it is reduced by a factor of grown on Cu substrate and transferred to a Cu grid. The around 150 to about 200 O &À1, which is close to reported CVD selected area electron diffraction (SAED) pattern in Fig. 2A graphite on a Co catalyst.19 This thickness-dependent electro- exhibits that the product is of the hexagonal crystalline struc- nic property could be employed to design carbon electronics. ture of graphene. Fig. 2B is a high-resolution TEM (HRTEM) Graphene/graphite structures can be employed as field- image. Crystal lattice fringes can be observed in the image. In effect transistors (FETs), where graphene serves as active chan- order to clearly examine the lattice structure of the sample, the nels, and graphite, as electrodes.19 With our method, it is very Fourier filtered image of Fig. 2B is shown in Fig. 2C. It is clear easy to fabricate such structures and assemble them with the current photolithography technique, which is schematically displayed in Fig. 3A. As shown in Fig. 3A, 1.8 mm-thick photo-

resist pattern is firstly defined on SiO2/Si substrates with photolithography, and then annealed at 1000 1C under vacuum

and protection of H2/Ar gas flow. This leads to the photoresist pattern being transformed into around 180 nm-thick graphite with ultrathin carbon layers of 1.5 nm formed around it (step 2 in Fig. 3A). The growth of the ultrathin film is due to the above- mentioned CVD process, where the vaporized photoresist Fig. 2 (A) SAED pattern of the nanographene from photoresist, exhibiting an obvious hexagonal structure of graphene. (B) HRTEM image of the nano- molecules from the photoresist pattern are transported onto graphene from photoresist. Lattice fringes can be found in the image. (C) Fourier the contiguous parts resulting in ultrathin few-layer graphene filtered image of that indicated in B. formed around the photoresist on almost the whole substrate.

2790 Chem. Commun., 2013, 49, 2789--2791 This journal is c The Royal Society of Chemistry 2013 ChemComm Communication

can be easily and accurately defined and assembled. This easy approach to design graphene/graphite patterns should be helpful in developing pure carbon electronics. The work was supported by NSFC (11104204, 91121010), Shanghai Pujiang Program (12PJ1408900), the Fundamental Research Funds for the Central Universities (1370219139) and the Program for Changjiang Scholars and Innovative Research Team in University (IRT0964). Notes and references

1 A. K. Geim and K. S. Novoselov, Nat. Mater., 2007, 6, 183–191. 2 K.S.Novoselov,A.K.Geim,S.V.Morozov,D.Jiang,Y.Zhang,S.V. Dubonos, I. V. Grigorieva and A. A. Firsov, Science, 2004, 306, 666–669. 3 Y. Zhang, Y.-W. Tan, H. L. Stormer and P. Kim, Nature, 2005, 438, 201–204. 4 P. Avouris, Z. Chen and V. Perebeinos, Nat. Nanotechnol., 2007, 2, 605–615. 5 X. Wang, Y. Ouyang, X. Li, H. Wang, J. Guo and H. Dai, Phys. Rev. Lett., 2008, 100, 206803. 6 C. Lee, X. Wei, J. W. Kysar and J. Hone, Science, 2008, 321, 385–388. 7 A. A. Balandin, S. Ghosh, W. Bao, I. Calizo, D. Teweldebrhan, F. Miao and C. N. Lau, Nano Lett., 2008, 8, 902–907. Fig. 3 (A) Schematic growth process of a graphene/graphite integrated circuit 8 S. Stankovich, D. A. Dikin, R. D. Piner, K. A. Kohlhaas, A. Kleinhammes, Y. Jia, Y. Wu, S. T. Nguyen and R. S. Ruoff, Carbon, on SiO2/Si substrate. (B) Optical microscope image of a graphene/graphite integrated circuit directly grown on SiO /Si substrate. The inset is the enlarged 2007, 45, 1558–1565. 2 9 W. Gao, L. B. Alemany, L. Ci and P. M. Ajayan, Nat. Chem., 2009, 1, image of the central part of the circuit. (C) I –V curves of the device dependent D DS 403–408. on different gate voltages. (D) Transfer characteristic curve of the device at the 10 C. Berger, Z. Song, X. Li, X. Wu, N. Brown, C. Naud, D. Mayou, T. Li, VDS of 0.5 V. J. Hass, A. N. Marchenkov, E. H. Conrad, P. N. First and W. A. de Heer, Science, 2006, 312, 1191–1196. 11 X. Li, W. Cai, J. An, S. Kim, J. Nah, D. Yang, R. Piner, By using photolithography alignment, the second photoresist A. Velamakanni, I. Jung, E. Tutuc, S. K. Banerjee, L. Colombo and R. S. Ruoff, Science, 2009, 324, 1312–1314. pattern is defined to cover the wanted parts (step 3 in Fig. 3A). 12 A. N. Obraztsov, Nat. Nanotechnol., 2009, 4, 212–213. After oxygen plasma etching and photoresist removal, the 13 A. Reina, X. Jia, J. Ho, D. Nezich, H. Son, V. Bulovic, designed graphene/graphite structures come into being. M. S. Dresselhaus and J. Kong, Nano Lett., 2008, 9, 30–35. 14 J. Kwak, J. H. Chu, J.-K. Choi, S.-D. Park, H. Go, S. Y. Kim, K. Park, Fig. 3B shows a typical optical microscope image of the S.-D. Kim, Y.-W. Kim, E. Yoon, S. Kodambaka and S.-Y. Kwon, Nat. assembled transistor arrays, which are grown on a 300 nm- Commun., 2012, 3, 645. thick thermal SiO dielectric on p-doped Si substrate. The 15 Z. Sun, Z. Yan, J. Yao, E. Beitler, Y. Zhu and J. M. Tour, Nature, 2010, 2 468, 549–552. electronic properties of the devices are characterized with a 16 J. Chen, Y. Wen, Y. Guo, B. Wu, L. Huang, Y. Xue, D. Geng, D. Wang, Keithley 4200 SCS semiconductor analyzer in air at room G. Yu and Y. Liu, J. Am. Chem. Soc., 2011, 133, 17548–17551. temperature, and the results are displayed in Fig. 3C and D. 17 L. Zhang, Z. Shi, Y. Wang, R. Yang, D. Shi and G. Zhang, Nano Res., 2011, 4, 315–321. The ID–VDS characteristic curves in Fig. 3C clearly show that the 18 K. S. Novoselov, V. I. Falko, L. Colombo, P. R. Gellert, M. G. Schwab conductance of the device increases with the gate voltage and K. Kim, Nature, 2012, 490, 192. decreasing from 20 V to À80 V. Fig. 3D is the corresponding 19 J.-U. Park, S. Nam, M.-S. Lee and C. M. Lieber, Nat. Mater., 2012, 11, 120–125. transfer characteristic curve of the device, which exhibits a 20 A. C. Ferrari and J. Robertson, Phys. Rev. B: Condens. Matter, 2000, slight ambipolar property with the neutrality point at around 61, 14095–14107. 40 V. The results indicate that the produced devices are p-type. 21 F. Yu, H. Q. Zhou, Z. X. Zhang, D. S. Tang, M. J. Chen, H. C. Yang, G. Wang, H. F. Yang, C. Z. Gu and L. F. Sun, Appl. Phys. Lett., 2012, The p-type behavior of our devices could be mainly due to the 100, 101904. defects in graphene, since p-type characteristic is often found 22 S. K. Jerng, D. S. Yu, Y. S. Kim, J. Ryou, S. Hong, C. Kim, S. Yoon, in reduced graphene FETs from graphene oxide.25,26 The mobi- D. K. Efetov, P. Kim and S. H. Chun, J. Phys. Chem. C, 2011, 115, 2 À1 À1 4491–4494. lity of the obtained film is around 4 cm V s , which is lower 23 M. H. Ru¨mmeli, A. Bachmatiuk, A. Scott, F. Bo¨rrnert, J. H. Warner, than typical CVD graphene, but comparable to graphene V. Hoffman, J.-H. Lin, G. Cuniberti and B. Bu¨chner, ACS Nano, 2010, obtained by the Hummers method.18 4, 4206–4210. 24 M. B. Va´zquez-Santos, E. Geissler, K. La´szlo´, J.-N. Rouzaud, In summary, we thus demonstrated a simple and cheap A. Martıńez-Alonso and J. M. D. Tascoń, J. Phys. Chem. C, 2011, method for controllable growth of nanocrystalline few-layer 116, 257–268. graphene (or graphite) films with different thicknesses from 25 Z. Zhang, Z. Sun, J. Yao, D. V. Kosynkin and J. M. Tour, J. Am. Chem. Soc., 2009, 131, 13460–13463. photoresist without catalyst on variable substrates. With the 26 X. Li, H. Wang, J. T. Robinson, H. Sanchez, G. Diankov and H. Dai, current photolithography method, graphene/graphite patterns J. Am. Chem. Soc., 2009, 131, 15939–15944.

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