J Mater Sci

Few-layer graphene films prepared from commercial copper foil tape J. J. Vivas-Castro1,*, G. Rueda-Morales1, G. Ortega-Cervantez1, L. A. Moreno-Ruiz2, and J. Ortiz-Lo´pez1 1 2

Departamento de Física, Instituto Politécnico Nacional, ESFM, Edificio 9, U.P.A.L.M., 07738 Mexico City, Mexico Instituto Politécnico Nacional, Centro de Nanociencias y Micro-Nanotecnologías, Av. Luis Enrique Erro S/N, U.P.A.L.M., 07738 Mexico City, Mexico

Received: 20 October 2016

ABSTRACT

Accepted: 16 December 2016

We present a facile, versatile and cost-effective method for the synthesis of mono- and bilayer graphene films on copper substrate using as carbon feedstock the pyrolysis products of the conductive adhesive polymer of a commercial copper tape commonly used in electron microscopy. A copper tape with adhesive on both sides is subjected to a heat treatment during 15 min at temperatures of 900, 1000, and 1050 °C under the flow of an Ar ? 3%H2 gas mixture. With this treatment, the tape adhesive polymer is pyrolized and the interaction of its decomposition products with the copper substrate gives rise to a graphene film of good structural quality mixed with amorphous carbon residues of the pyrolysis. For a temperature of 1050 °C (few degrees below the melting point of Cu), mono- and bilayer coexisting domains of graphene are obtained with almost 100% area coverage of the Cu substrate. For lower heat treatment temperatures, area coverage is reduced to 60–70% and the graphene film becomes predominantly bilayer. The treatment at the lowest temperature of 900 °C results in isolated hexagonal domains of graphene intermixed with a large amount of amorphous carbon residues and large uncovered areas of oxidized copper substrate. These results indicate that the number of active species for the formation of graphene films increases with increasing temperature, nevertheless limited by the copper melting point. Characterization of the obtained samples was performed with scanning electron microscopy, Raman scattering, and high-resolution transmission electron microscopy.

Ó

Springer Science+Business

Media New York 2016

Introduction Since the first method to isolate graphene by micromechanical cleavage of HOPG [1], several other methods of synthesis have been developed, such as

Address correspondence to E-mail: [email protected]

DOI 10.1007/s10853-016-0683-0

thermal decomposition of SiC [2], reduction of graphene oxide [3], and growth of graphene by CVD using different transition metals as substrate [4, 5]. Graphene synthesis on polycrystalline Cu using heat treatments offers a great opportunity for the

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growth of large-area, good structural quality single or few-layer films [6]. Annealing Cu substrates covered with a nanometer-thick film of poly-methyl methacrylate (PMMA) or other solid carbon sources to temperatures above 800° C yields good quality single-layer graphene [7]. However, to achieve such films requires deposition techniques such as spincoating, lithographic patterning [8] or ion implantation of C into Cu [9]. Moreover, it has been reported that the growth temperature plays an important role in the nucleation density, growth rate, percentage of coverage, and the number of layers of graphene film [10]. In this approach, the annealing temperature plays an important role affecting the density of nucleation sites, growth rate, coverage, and number of layers of the resulting graphene film. In this paper, we propose a facile single-step method to grow few-layer graphene using a commercial self-adhesive copper foil conductive tape commonly used in scanning electron microscopy in which the tape adhesive acts as carbon source. In this procedure, the copper tape is simply heated under the flow of an Ar and H2 gas mixture to temperatures just below the copper melting point and a graphene film grows on the copper surface from the pyrolysis products of the adhesive material. With this method, there is no need for cleaning the copper substrate nor to deposit any precursor on the copper substrate prior to synthesis. By using a double-sided adhesive tape, it is possible to grow graphene films on both sides of the copper foil. The adhesive material in the copper foil tape is an electrically conductive pressuresensitive acrylic whose exact composition is an industrial trade secret [11, 12]. However, as any acrylic compound, it decomposes at high temperatures providing the carbon source for graphene synthesis. In addition, the conductive adhesive acrylic contains highly conductive particles [11], which appear as residues of pyrolysis without substantially affecting graphene film growth. Since chemical composition of the acrylic adhesive should be very close to that of PMMA, our proposed method is in many respects equivalent to those that use a PMMA thin film on copper to grow graphene [7]. Within the proposed method, we show that the synthesis temperature plays an important role in coverage, number of layers, and structural quality of graphene on the surface of the Cu substrate. At a synthesis temperature of 1050 °C (about 35 °C below copper melting temperature), monolayer and bilayer

coexisting graphene films were obtained with excellent structural quality and almost complete coverage on the Cu substrate. For a threshold temperature of 900 °C, only small bilayer graphene domains are obtained accompanied with a substantial amount of amorphous carbon and uncovered areas of copper oxide.

Experimental For single and bilayer graphene synthesis on copper substrate, we employed a 1/4 in wide, 1/64 in (40 lm) thick copper foil conductive tape with adhesive on both sides (Tape 1182, 3M Electrical Products Division) shown in Fig. 1a, which is commonly used in scanning electron microscopy. To support a piece of tape, we used a fused quartz tube section cut along its diameter, as shown in Fig. 1b. This mounting geometry allows the growth of graphene on both upper and lower surfaces of the copper foil. The sample arrangement is inserted into a 1.4 cm inner diameter quartz tube, which in turn is inserted inside a cylindrical oven. For the synthesis, temperature is initially raised to 750 °C while the quartz tube is kept under dynamic vacuum. After few minutes, the tube is filled with an Ar/H2(3%) gas mixture and the Cu foil is placed inside the quartz tube close to the center of the furnace. The temperature is then raised and maintained during 15 min at a temperature of synthesis to 900, 1000, and 1050 °C (just below the melting point of Cu) while a flow of Ar/H2 gas mixture is maintained at rate of about 500 sccm. The system is finally cooled down to 200 °C at a rate of about 1 °C/s keeping the flow of the gas mixture for a while, as illustrated in Fig. 1c. The adhesive material in the copper foil tape is an electrically conductive pressure-sensitive acrylic whose exact composition is an industrial trade secret [11, 12]. According to manufacturer’s specifications, the adhesive in the copper foil conductive tape is 25-lm thick on each side [11]. The Raman spectrum of the adhesive shown in Fig. 1d displays features that confirm its acrylic composition, similar to those of PMMA. Typical vibrational modes of PMMA, corresponding to C–H (372–1447 cm-1 deformation, 1035–1337 cm-1 twisting, 1153 cm-1 wagging, 824–915 cm-1 rocking, and 2721–2957 cm-1 stretching), C–C (979 and 1596 cm-1), C–O (731 and

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Figure 1 a Photograph of the copper foil conductive adhesive tape used in the experiments. b Experimental arrangement used for the synthesis of graphene films from the copper tape. c Schematic

diagram of the heat treatments applied to the copper tape. d Raman spectra of the polymer adhesive of the copper tape which identifies it as a PMMA derivative.

1269 cm-1), and C=O (745 and 1728 cm-1) bonds are clearly present in the spectrum of Fig. 1d [13]. Weak bands not attributed to PMMA, located at 1640 cm-1 and in the 420–460 cm-1 range, may be tentatively assigned to phenyl ring (Ph) stretching and ring deformation modes (modes 21 and 18), respectively [14]. We speculate that the phenyl group may perhaps act as a seed group expediting self-assembly in graphene synthesis. Additionally, we detect some weak low frequency modes in the 200–340 cm-1 range that we attribute to copper oxide coming from metallic copper particles blended with the adhesive to make it conductive [11, 15–18]. The conductive adhesive is then probably a blend between dispersed copper particles and a polymer or copolymer containing a methyl and benzyl methacrylate units.

Pyrolysis of the acrylic adhesive is expected to occur around 310 °C, if we take the case of PMMA as benchmark [19]. An important requisite for the synthesis of graphene films from a polymer precursor is that its backbone must consist entirely of carbon atoms formed with simple aliphatic C–C bonds characterized by low bond dissociation energies, rather than formed with double, triple or aromatic/ heterocyclic C–C bonds which have higher bond dissociation energies [20]. The obtained graphene films on copper substrates were characterized by scanning electron microscopy (SEM) using a FEI-Sirion instrument operated at 5 kV with secondary electrons. Raman spectra and maps were measured directly from the prepared samples with a Labram HR800 (Horiba Jobin Yvon)

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equipment with 633 nm excitation. For Raman spectra, a 509 objective and 1.03 lm spot was used and Raman mapping was performed in 1.5 lm steps with 1009 objective and a 0.86 lm spot. For high-resolution transmission electron microscopy (HRTEM), a JEM-ARM200CF (JEOL) microscope was used. TEM samples were prepared by depositing a drop of ethanol directly on the sample (graphene film on copper substrate) on top of which a holey carbon-300 mesh TEM grid was placed. The grid was lifted off when the ethanol drop dried. With this procedure, some graphene flakes are transferred to the TEM grid.

Results In the proposed method of synthesis, the growth temperature plays an important role in the number of layers, structural quality, and coverage of the resulting graphene film on the copper substrate. By subjecting a copper tape with adhesive on both sides to 1050 °C, graphene films grow on both sides of the copper substrate. In reference to the arrangement described in Fig. 1, in Fig. 2a, we show a SEM image of a graphene film grown at 1050 °C on the upper face of the copper foil. The obtained graphene film shows full area coverage (dark contrast) and a multidomain structure with domain sizes no larger than 2 lm, separated by thin bright boundaries. The bright spots also seen in Fig. 2a correspond to rounded particles with diameters in the 50–200 nm range (see magnification in the inset). As will be discussed below, these particles correspond to amorphous carbon residues after thermal decomposition of the adhesive and represent the main source of carbon in the formation of graphene films. The image in Fig. 2b taken with backscattered electrons allows the observation of characteristic wrinkles of graphene grown on the Cu substrate in bright contrast. The dark spots on this image correspond to leftovers from the heat treatment, mostly composed of amorphous carbon as mentioned previously. This is in accord with previously reported results on graphene synthesis (for temperatures between 400 and 750 °C) using nanometer-thick PMMA films as solid precursor on Cu substrates [8, 21]. In our case, the adhesive film is considerably thicker (*25 lm) so that a considerable amount of these residues is observed.

For the same sample, the graphene film obtained on the lower face of the copper tape is shown in Fig. 2c. Uncovered areas of the Cu substrate are seen in gray color and indicate a lesser area coverage than for the upper face. Domains of hexagonal shape in dark contrast have regular and sharply defined boundaries. Distribution of domain sizes is more homogeneous for the lower film, ranging from 1 to 2 lm. These variations in graphene film coverage grown on the upper and lower parts of the copper tape are due to different exposure conditions to Ar/ H2 gas flow. The presence of wrinkles in the graphene film is clearly seen in the domain highlighted by the white rectangle in Fig. 2c. These wrinkles come about at the end of the synthesis process because upon cooling, the Cu tape shrinks and creates stress on the graphene film. The inset of Fig. 2c shows the topographical profile of the wrinkles along the indicated yellow path inside the domain. For a lower synthesis temperature of 1000 °C, graphene film coverage is notoriously reduced to the 60–70% range as illustrated in Fig. 2d, taken with the same magnification as Fig. 2a. Graphene film is identified with dark contrast while Cu substrate is in lighter contrast. Larger spots of residues (enclosed with white rectangles) are seen in Fig. 2d having 5–25 lm sizes. To investigate the nature of these residuals, in the image of Fig. 2e, we show an amplified view of one of them with backscattered electrons. The residual is composed of small bright particles of 100–500 nm embedded in a round dark matrix. The elemental chemical analysis by energydispersive X-ray spectroscopy (EDS) of this residual shown in Fig. 2f indicates that its composition is only of Cu, O, and C. Since the conductive adhesive is made from a PMMA derivative blended with copper particles, we deduce that the residuals are formed by oxidized Cu nanoparticles embedded in a carbon matrix (most seemingly amorphous) that did not end up participating in the assemblage of the graphene film. For an even lower synthesis temperature of 900 °C, pyrolysis of the adhesive is not complete and few graphene domains are found (\20% area coverage), surrounded by large areas of oxidized Cu substrate, as illustrated in the image of Fig. 2g. The electronbackscattered image of Fig. 2h shows (enclosed by a black square) details of residual material composed of an amorphous carbon matrix with embedded oxidized copper nanoparticles of the conductive

J Mater Sci

Figure 2 a SEM image of a graphene film grown at 1050 °C on the upper face of the copper foil. The film shows a multidomain structure separated by thin bright boundaries. The bright spots are leftovers from pyrolysis of the conductive polymer adhesive (see magnification in the inset). b Backscattered electron SEM image showing characteristic wrinkles of graphene grown on the Cu substrate. The dark spots on this image are leftovers of pyrolysis. c SEM image of the lower face of the copper tape. Hexagonal graphene domains are seen in dark contrast and uncovered areas of the Cu substrate are seen in lighter contrast. The white rectangle marks the presence of wrinkles in the graphene film whose topographical profile is shown in the inset. d SEM image of graphene film grown at 1000 °C showing a reduced area coverage. Large spots of pyrolysis residuals are enclosed with white

rectangles. e Backscattered electron image of an amplified view of one of the spots in d; the residual is composed of small bright particles embedded in a round dark matrix. f Energy-dispersive X-ray spectroscopy (EDS) elemental chemical analysis of residual shown (e). g SEM image of sample prepared at 900 °C, few graphene domains are found surrounded by large areas of oxidized Cu substrate. h Electron-backscattered image of pyrolysis residuals of the conductive adhesive, composed of an amorphous carbon matrix with embedded oxidized copper nanoparticles. The inset shows a magnified view of a portion of the residue. i EDS analysis of the sample prepared at 900 °C, very similar to the one prepared at 1000 °C, except for an increased intensity of O signal originating from large exposed areas of the oxidized copper substrate.

adhesive, as discussed above. The mosaic pattern in two tones of gray are crystalline domain regions of the oxidized copper substrate, some of them containing isolated graphene islands. The EDS analysis presented in Fig. 2i is quite similar to the one discussed for the sample prepared at 1000 °C (Fig. 2h)

except for an increased intensity of O signal originating from large exposed areas of the oxidized copper substrate due to reduced coverage of the graphene film [22]. To assess the number of layers and structural quality of graphene films, we took Raman scattering

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Figure 3 a Typical Raman spectra of mono- and bilayer graphene films taken from regions of samples in which graphene was detected. b Single Lorentzian fit of the 2D Raman band for monolayer graphene film. c Four Lorentzian fit of the 2D Raman

band of bilayer graphene film. d Characteristic Raman spectra taken from regions where graphene was not detected showing the presence of amorphous carbon and copper oxides.

spectra on several spots of both sides of the copper foil. All samples prepared at 1050, 1000, and 900 °C contain single- and double-layer graphene films, although the 900 °C sample has them in much less amount. Figure 3a shows representative measured spectra of single- and double-layer graphene, corresponding to films grown on the upper face of samples prepared at 1050 and 1000 °C, respectively. Three characteristic bands are featured in the 1100–3000 cm-1 spectral range, corresponding to the D, G, and 2D bands of graphene [23–25]. The defectinduced D band around 1325 cm-1 is related to longitudinal optical phonons (LO) around K or K’ points of the Brillouin zone [26, 27] made active by structural defects mainly located at the edges of

graphene domains. Meanwhile, the G band around 1582 cm-1 is due to the in-plane vibrational mode of sp2 carbon C–C bonds and the 2D band around 2638 cm-1 is typically the most prominent band in few-layer graphene, due to a second-order degenerated phonon process (iTO and LO) involving two iTO phonons near the K point of the Brillouin zone [28]. The 2D band for bilayer graphene is seen displaced to a slightly higher frequency of 2645 cm-1 [29]. For monolayer and bilayer graphene of good structural quality, the intensity relation I2D/IG between 2D and G bands is typically between 2 and 4, being smaller for bilayer [23]. As shown in Fig. 3b, the 2D band for our monolayer film is symmetric, has a I2D/IG = 2.5, and can be fitted with

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a single Lorentzian with a FWHM of 32 cm-1, similar to what Liu et al. have reported [30]. In contrast, the obtained bilayer film in Fig. 3c has a I2D/ IG = 1.6 with a wider FWHM (*50 cm-1) and is asymmetric, in good agreement with the work of Yu et al. [31]. In addition, the bilayer 2D band is well fitted with four Lorentzians at 2620, 2635, 2648, and 2660 cm-1 corresponding to processes involving interlayer interactions [24, 30]. Caution must be exercised when taking relative intensity of Raman I2D and IG bands as lone signature of monolayer and bilayer graphene. Relevant in this respect is the work of Yin et al. [32] who report that Raman I2D/IG intensity ratio may change up to an order of magnitude due to the presence of CuO and Cu2O films when the substrate is exposed to ambient conditions for long periods of time. In our case, however, our Raman spectra were taken immediately after synthesis so that copper oxide films should not be important in the Raman signal, as confirmed by the lack of signal of CuO and Cu2O (149, 225, and 645 cm-1) in Fig. 3a. The intensity ratio I2D/IG as well as the FWHM of 2D band also depend on stacking order of layers in bilayer graphene as described by Bayle et al. [33]. If stacking order is different from Bernal A–B stacking, the intensity ratio as well as FWHM of 2D band may be indistinguishable from characteristic values of monolayer graphene. Nevertheless, below we demonstrate the presence of mono- and bilayer graphene in our films using high-resolution transmission electron microscopy (HRTEM). For regions without graphene (mostly in samples grown at 900 and 1000 °C), the measured Raman signal is characteristic of amorphous carbon, as documented in Fig. 3d. Wide and weak D and G bands at 1326 and 1580 cm-1 are observed, together with new peaks appearing at low frequency that are identified as due to the presence of copper oxide CuO [15–17], while the band at 225 cm-1 corresponds to cuprous oxide copper Cu2O [18]. To analyze the homogeneity of the graphene films, we applied Raman mapping that resulted in the images shown in Fig. 4 taken on the upper faces of the copper foil. Examination of lower faces of the copper foil yielded similar analysis results. Columns (a), (b), and (c) in Fig. 4 correspond to samples synthesized at 1050, 1000, and 900 °C, respectively. Scanned areas in columns (a) and (b) show images of a 130 9 130 lm2 area, while column (c) corresponds

to an area of 25 9 25 lm2. The upper first row in Fig. 4 shows optical microscopy (OM) images of the scanned areas and the following rows show consecutive Raman maps of I2D/IG, 2D band FWHM, and IG/ID of the corresponding scanned regions shown in the first row. For the sample prepared at 1050 °C in column (a), the OM image shows a clearly different contrast dividing the image in almost two equal parts having a diagonal boundary that we have marked with a black line. This analyzed region corresponds to the neighborhood of a boundary between one region largely made of single-layer graphene in the left diagonal side and a region of predominant bilayer graphene on the other side. This is concluded by looking at the sequence of images below the OM image in column (a). Along all these images, the boundary of these regions is clearly present and marked with a white diagonal line. In the region at the left, values between 2.2 and 2.9 for the I2D/IG ratio predominate in the Raman map while on the region at the left side the predominant values are 1.2–1.8. For the 2D band FWHM, the values are 30–38 cm-1 at the left side and 42–49 cm-1 at the right side. The intensity ratio IG/ID between the G band and D band is a measure of the structural quality of sp2 carbonaceous materials; the larger its value the better structural quality of the material is. In the last row of column (a), the Raman map of IG/ID indicates that its value varies in the 5–15 range at the left region, while it varies between 1 and 5 on the right region. Given the values of the various Raman features revealed by the maps for this sample, it is concluded that to the left of the boundary the graphene film is mostly monolayer of good structural quality and to the right is mostly bilayer, as documented by various authors [34–36]. For the sample prepared at 1000 °C, similar examination of the Raman maps in column (b) of Fig. 4 reveals an analyzed region of good homogeneity, as seen directly by the OM image. For this sample, the I2D/IG is in the 1.4–1.8 range and the 2D band FWHM ranges between 45 and 55 cm-1, which points to a predominant bilayer graphene film with a relatively good structural quality with a IG/ID between 4 and 14. Finally, in Fig. 4c, a complete hexagonal domain is examined for the sample prepared at 900 °C. From the Raman maps, it is seen that the graphene film is in its majority bilayer (about 90%) since I2D/IG has values mostly in the 1.2–2 range

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Figure 4 Sequence of images that describe the analysis of graphene films obtained on the upper face of the copper foil with optical microscopy (OM) and Raman spectroscopy mapping. Column a corresponds to sample prepared at 1050 °C. Column b to sample prepared at 1000 °C. Column c to sample prepared at 900 °C. The first row is an optical image of the area analyzed for

each sample and the sequence of rows below show Raman mapping images of the same area observed with OM. Images below first row display in sequence the behavior of the intensity relation I2D/IG between Raman 2D and G bands, the Raman 2D band FWHM, and the intensity relation IG/ID between the Raman G and D bands.

and the 2D band FWHM is between 30 and 50 cm-1, while the structural quality is relatively good with a IG/ID between 2 and 10.

To confirm the presence of mono- and bilayer graphene in our synthesized films, an HRTEM image of a (partially transferred) film synthesized at 1050 °C

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Figure 5 a HRTEM image of transferred film synthesized at 1050 °C (scale bar indicates 1 nm). b Amplification of selected area with fast Fourier transform at the right-hand side showing that is monolayer graphene. c Amplification of selected area with fast Fourier transform at the right-hand side showing that is bilayer graphene with 14° stacking rotation between layers.

is presented in Fig. 5a, clearly showing the typical periodic structure of graphene. Figure 5b, c shows the magnified views of selected areas in Fig. 5a. Applying 2D fast Fourier transform to these areas results in the diffraction patterns shown at the righthand side, which prove the presence of mono- and bilayer graphene in Fig. 5b, c, respectively. For bilayer graphene, careful analysis of Fig. 5c shows two superposed patterns indicating a 14° stacking rotation between the layers [37, 38].

Discussion From SEM and Raman analyses, we find that coverage and layer number of synthesized graphene films show a clear dependence on the temperature of preparation. When the copper foil tape is introduced into the preheated system at 750 °C, the adhesive contracts, while volatile components evaporate and remaining carbonaceous residues form agglomerates on the copper substrate and act as carbon source for the growth of graphene. Undeniably, carbon source in our method is the amorphous carbon residues leftover from the thermal decomposition of the adhesive compound. Since the adhesive of the copper tape is a PMMA compound derivative, as seen from our Raman analysis, graphene film growth mechanisms in our method are similar to those considered in methods where graphene growth is obtained from PMMA nanometer-thick thin films on copper [8, 21].

However, because of the different chemical compositions and much greater thickness of the adhesive compound (25 lm) in our method, the breakage of carbon bonds that result in active graphene-forming species is more complicated. At a temperature of 900 °C, a great amount of amorphous carbon agglomerated residues dispersed over large areas of oxidized copper substrate. At these low temperatures, active carbon species have low mobility and are only able to reach a state of disordered carbon agglomerates. Similar effects have also been observed by other authors [39, 40]. As temperature of synthesis is increased, thermal decomposition of the adhesive compound is more effective, leaving smaller carbon residues since carbon active species with increased mobility become able to participate in the formation of graphene (see Fig. 6). The flow of Ar/H2 gas mixture must also be taken into account since H2 may react with carbon active species of the adhesive residues to produce volatile hydrocarbons that may participate as a secondary source of carbon in the growth of graphene in a CVD-like process. The contribution of active carbon precursors to graphene growth is expected to be rather insensitive to temperature of synthesis since carbon adsorption energy to the Cu substrate is rather small (0.02 eV). However, the contribution of hydrocarbon precursors should be more important at higher temperatures because breakage of C–H bonds to create carbon active species require more energy [39]. This may explain why in our case graphene area coverage

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Figure 6 Schematic representation of the growth mechanism of few-layer graphene from copper adhesive tape.

increases with increasing temperature. On the other hand, Cho et al. [40] have reported that at high temperatures, copper oxides as well as hydrocarbon residues may be removed during the synthesis, which is also what we observe in our case.

acknowledge the Centro de Nanociencia y MicroNanotecnologia of IPN for HRTEM and SEM analyses.

References Conclusions We demonstrate the effectiveness of the growth method of mono and bilayer graphene from a commercial double-sided adhesive copper tape commonly used in electron microscopy. Our findings show that the pyrolysis of the PMMA-derivative copper tape adhesive polymer delivers an adequate feedstock for the growth of high quality graphene, providing an added value to this laboratory product. The treatment temperature is an important parameter in the growth process that influences both the area coverage and the number of layers of the synthesized graphene film. A schematic description of the growth mechanism is proposed for the formation of graphene films as a function of temperature of synthesis.

[1]

[2]

[3]

[4]

[5]

[6]

Acknowledgements

[7]

JJVC is thankful to CONACyT-Mexico for a graduate student scholarship, while the other authors wish to thank SIP-IPN, COFAA-IPN/SIBE, and EDI-IPN for partial financial support. The authors gratefully

[8]

Novoselov K, Geim A, Morozov S, Jiang D, Zhang Y, Dubonos S, Grigorieva I, Firsov A (2004) Electric field effect in atomically thin carbon films. Science 306:666–669 Berger C, Song Z, Li X et al (2006) Electronic confinement and coherence in patterned epitaxial graphene. Science 312:1191–1195 Chua CK, Martin Pumera M (2014) Chemical reduction of graphene oxide: a synthetic chemistry viewpoint. Chem Soc Rev 43:291–312 Reina A, Jia X, Ho J et al (2009) Layer area, few layer graphene films on arbitrary substrate by chemical vapor deposition. Nano Lett 9:30–35 Yu Q, Lian J, Siriponglert S et al (2008) Graphene segregated on Ni Surface and transferred to insulators. Appl Phys Lett 93:113103–113105 Prekodravac J, Markovic Z, Jovanovic S et al (2015) The effect of annealing temperature and time on synthesis of graphene thin films by rapid thermal annealing. Synth Met 209:461–467 Sun Z, Yan Z, Yao J et al (2010) Growth of graphene from solid carbon sources. Nature 468:549–552 Wu W, Jauregui LA, Su Z et al (2011) Growth of single crystal graphene arrays by locally controlling nucleation on polycrystalline Cu using chemical vapor deposition. Adv Mater 23:4898–4903

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[9]

[10]

[11]

[12] [13]

[14]

[15]

[16]

[17]

[18]

[19] [20] [21]

[22]

[23] [24]

[25]

Lee JS, Jang CW, Kim JM et al (2014) Graphene synthesis by C implantation into Cu foils, graphene synthesis by ion implantation. Carbon 66:267–271 Xing S, Wu W, Wang Y et al (2013) Kinetic study of graphene growth: temperature perspective on growth rate and film thickness by chemical vapor deposition. Chem Phys Lett 580:62–66 Data Sheet, 1182 Tape copper foil, conductive adhesive on both sides, 3M Electrical Products Division, www.3m.com/ elpd M Electrical tape, Article Information Sheet, 3M Electrical Products Division, www.3m.com/elpd Haris MR, Kathiresan S, Mohan S (2010) FT-IR and FTRaman spectra and normal coordinate analysis of poly methyl methacrylate. Der Pharma Chem 2:316–323 Łapinski A, Spanget J, Langga˚rd Morten, Waluk J, Radziszewski JG (2001) Raman spectrum of the phenyl radical. J Phys Chem A 105(46):10520–10524 Francisco MS, Mastelaro VR (2001) Activity and characterization by XPS, HR-TEM, Raman spectroscopy, and BET surface area of CuO/CeO2-TiO2. J Phys Chem B 105:10515–10522 Larsson PO, Arne A (1998) Complete oxidation of CO, ethanol, and ethyl acetate over copper oxide supported on titania and ceria modified titania. J Catal 179:72–89 Wang Z, Pischedda V, Saxena SK, Lazor P (2002) X-ray diffraction and Raman spectroscopic study nanocrystalline CuO under pressures. Solid State Commun 121:275–279 Vera LP, Pe´rez JA, Riascos H (2013) Ana´lisis espectrosco´pico de las pelı´culas delgadas de o´xido de cobre y del plasma producido por deposicio´n de la´ser pulsado. Rev Colomb Fis 45:146–150 Mark JE (2007) Physical properties of polymers handbook. Springer, New York, pp 927–938 Sun JB, Hyunseob L, Ga-Young S (2011) Graphenes converted from polymers. J Phys Chem Lett 2:493–497 Li ZC, Wu P, Wang CX et al (2011) Low-temperature growth of graphene by chemical vapor deposition using solid and liquid carbon sources. ACS Nano 5:3385–3390 Chen S, Brown L, Levendorf M et al (2011) Oxidation resistance of graphene-coated Cu and Cu/Ni alloy. ACS Nano 5:1321–1327 Ferrari AC, Meyer JC, Scardaci V et al (2006) Raman spectrum of graphene and graphene layers. Phys Rev Lett 97:1–4 Gupta A, Chen G, Joshi P et al (2006) Raman scattering from high-frequency phonons in supported n-graphene layer films. Nano Lett 12(6):2667–2673 Malard LM, Pimenta MA, Dresselhaus G, Dresselhaus MS (2009) Raman spectroscopy in graphene. Phys Rep 473:51–87

[26] Ding F, Ji HX, Chen YH et al (2011) Stretchable graphene: a close look at fundamental parameters through biaxial straining. Nano Lett 10:3453–3458 [27] Ferrari AC (2007) Raman spectroscopy of graphene and graphite: disorder, electron–phonon coupling, doping and nonadiabatic effects. Solid State Commun 143:47–57 [28] Ferrari AC, Meyer JC, Scardaci Vet al (2006) Raman spectrum of graphene and graphene layers. Phys Rev Lett 97:1874011–187401-4. doi:10.1103/PhysRevLett.97.187401 [29] Park JS, Reina A, Saito R et al (2009) G0 band Raman spectra of single, double and triple layer graphene. Carbon 47:1303–1310 [30] Liu W, Li H, Xu C et al (2011) Synthesis of high-quality monolayer and bilayer graphene on copper using chemical vapor deposition. Carbon 49:4122–4130 [31] Yu Q, Jauregui LA, Wu W et al (2011) Control and characterization of individual grains and grain boundaries in graphene grown by chemical vapor deposition. Nat Mater 10:443–449 [32] Yin X, Li Yi, Ke F et al (2014) Evolution of the Raman spectrum of graphene grown on copper upon oxidation of the substrate. Nano Res 7(11):1613–1622 [33] Bayle M, Reckinger N, Huntzinger JR, Felten A, Bakaraki A, Landois P, Colomer JF, Henrard L, Zahab AA, Sauvajol JL, Paillet M (2015) Dependence of the Raman spectrum characteristics on the number of layers and stacking orientation in few-layer graphene. Phys Status Solidi B 252:2375–2379 [34] Yan K, Peng H, Zhou Y, Li H, Liu Z (2011) Formation of bilayer bernal graphene: layer-by-layer epitaxy via chemical vapor deposition. Nano Lett 11:1106–1110 [35] Murdock AT, Koos A, Britton TB et al (2013) Controlling the orientation, edge geometry, and thickness of chemical vapor deposition graphene. ACS Nano 2(7):1351–1359 [36] Lee S, Lee K, Zhong Z (2010) Wafer scale homogeneous bilayer graphene films by chemical vapor deposition. Nano Lett 10:4702–4707 [37] Muramatsu H, Kim YA, Yang KS, Cruz-Silva R, Toda I, Yamada T, Terrones M, Endo M, Hayashi T, Saitoh H (2014) Rice husk-derived graphene with nano-sized domains and clean edges. Small 10(14):2766–2770 [38] Gu W, Zhang W, Li X (2009) Graphene sheets from wormlike exfoliated graphite. J Mater Chem 19:3367–3369 [39] Cui T, Lv Ruitao, Zheng HH et al (2012) Low-temperature synthesis of multilayer graphene/amorphous carbon hybrid films and their potential application in solar cells. Nanoscale Res Lett 7:453-1–453-7. doi:10.1186/1556-276X-7-453 [40] Cho J, Gao L, Tian J et al (2011) Atomic-scale investigation of graphene grown on Cu foil and the effects of thermal annealing. ACS Nano 5:3607–3613