Transparent Conducting Graphene Hybrid Films To Improve

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Transparent conducting graphene hybrid films to improve electromagnetic interference (EMI) shielding performance of graphene Limin Ma, Zhengang Lu, Jiubin Tan, Jian Liu, Xuemei Ding, Nicola Black, Tianyi Li, John C. Gallop, and Ling Hao ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.7b09372 • Publication Date (Web): 11 Sep 2017 Downloaded from http://pubs.acs.org on September 12, 2017

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ACS Applied Materials & Interfaces

Transparent Conducting Graphene Hybrid Films to Improve Electromagnetic Interference (EMI) Shielding Performance of Graphene Limin Ma,†, ‡ Zhengang Lu,*† Jiubin Tan,† Jian Liu,† Xuemei Ding,† Nicola Black,‡ Tianyi Li,‡ John Gallop,‡ and Ling Hao‡ †

Ultra-Precision Optical and Electronic Instrument Engineering Centre, Harbin Institute of

Technology, Harbin, 150001, People’s Republic of China. ‡

National Physical Laboratory, Hampton Road, Teddington, TW11 0LW, United Kingdom.

KEYWORDS: graphene, metallic network, EMI shielding, optical transparency, hybrid film.

ABSTRACT

Conducting graphene-based hybrids have attracted considerable attention in recent years for their scientific and technological significance in many applications. In this work, conductive graphene hybrid films, consisting of a metallic network fully encapsulated between monolayer graphene and quartz-glass substrate were fabricated and characterized for their electromagnetic interference shielding capabilities. Experimental results show that by integration with a metallic

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network, the sheet resistance of graphene was significantly suppressed from 813.27 Ω/sq to 5.53 Ω/sq with an optical transmittance at 91%. Consequently, the microwave shielding effectiveness (SE) exceeding 23.60 dB at Ku-band, and 13.48 dB at Ka-band. The maximum SE value was 28.91 dB at 12 GHz. Compared with the SE of pristine monolayer graphene 3.46 dB, the SE of graphene hybrid film was enhanced by 25.45 dB (99.7% energy attenuation). At 94% optical transmittance, the sheet resistance was 20.67 Ω/sq and the maximum SE value was 20.86 dB at 12 GHz. Our results show that hybrid graphene films incorporate both high conductivity and superior electromagnetic shielding comparable to existing ITO shielding modalities. The combination of high conductivity and shielding along with the materials’ earth-abundant nature, and facile large-scale fabrication, make these graphene hybrid films highly attractive for transparent EMI shielding.

1. INTRODUCTION In recent decades, the understanding of electromagnetic fields and technologies has expanded significantly.1-3 Most electronic devices, regardless of intended daily operation, industrial manufacture or scientific research, can emit electromagnetic waves at radio frequencies in high quantities.4,5 Prominent studies in this field have suggested that such electromagnetic pollution may be harmful to human health.6 This ambient electromagnetic radiation can also interfere with other nearby precise electronic instruments or circuitry and negatively affect their lifetime and ability to function.7,8 To avoid these adverse effects, electromagnetic interference (EMI) shielding is becoming increasingly important.4-10 Among EMI shielding techniques, transparent EMI shielding is vital for optoelectronic devices with optical windows.11-17 Specific examples can be seen in aerospace equipment, medical devices, communication facilities, and electronic


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displays. One of the key challenges for transparent EMI shielding is how to achieve both strong shielding performance and good optical transmittance simultaneously. Transparent conductive oxides (TCOs), especially indium tin oxide (ITO), are the primary choice to respond to these demands. However, they suffer from limited abundance of indium, weak electromagnetic shielding effectiveness (SE), and poor UV and IR transmittance.18 Carbon-based nanomaterials such as graphene, carbon nanocoils, carbon nanofibres and carbon nanotube (CNT) have been widely studied and shown strong potential for transparent EMI shielding. This is due to their unique properties including high conductivity and aspect ratio, broadband transmission spectrum (Vis−IR), mechanical durability, flexibility, and environmental stability.19-23 In particular, graphene has been seen as a potential substitute for ITO in the broader field of transparent conductors.24-29 However, the SE of monolayer graphene is only 2.27 dB when produced by chemical vapour deposition (CVD) in the microwave range,30,31 which is insufficient for most EMI shielding applications require SE larger than 10 dB or even larger than 20 dB at some cases. Moreover, a majority of the reported graphene-based materials for EMI shielding are opaque or offer poor transparency for high EMI SE.32-34 Recently attempts have focused on improving the EMI shielding performance of transparent graphene-based materials to address these issues.30-41 An example can be seen in work done by Hong et al. which showed a SE of 6.91 dB at 2.2−7 GHz for triple-layer CVD graphene.30 Kim et al. also reported a SE of 6.37 dB at 0.5−8.5 GHz with a light transmittance of 62% for reduced graphene oxide (RGO) sheets interleaved between polyetherimide (PEI) films fabricated by electrophoretic deposition (EPD).35 Moon et al. reported an average of 15 dB rejection with >70% visible transparency for a few layers of epitaxial graphene at 12–18 GHz.38


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EMI shielding performance is related to materials’ sheet resistance (Rs), with lower Rs values leading to higher shielding performance due to the higher conductivity.37,42 Based on theoretical analysis, Hong et al suggested that the SE of monolayer graphene could be improved from 2.27 dB to 16.5 dB with a decrease in Rs from 635 Ω/sq to its theoretical minimum of 30 Ω/sq.24 However, with current limitations in manufacturing technology, such high quality graphene is yet unattainable. Currently the Rs of monolayer graphene produced by scalable production methods, including CVD and epitaxial growth, is on the order of hundreds of Ω/sq, and above the ideal 30 Ω/sq.34,43,44 For RGO the Rs is even higher.45 In order to bring graphene closer to meet these demands of high conductivity and transparency various strategies have been reported.46-50 For instance, Bult et al. reported a RS of ∼50 Ω/sq at 89% visible transmittance achieved for four-layer chemically doped n- or p-type graphene transparent conducting electrodes (TCs).51 Deng et al. also fabricated TCs based on a metallic nanowire network encapsulated between monolayer graphene and a plastic substrate, which achieved RS of ∼8 Ω/sq at 94% transmittance.52 Lastly, Ahn et al. reported a RS of 53.8 Ω/sq with 89.3% transmittance at 550 nm for a copper nanowire- graphene core-shell nanostructure synthesized using lowtemperature plasma-enhanced CVD process.53 In the work presented here, we demonstrate that the sheet resistance of monolayer graphene can be significantly reduced and EMI shielding performance consequently improved through the construction of graphene hybrid films. This graphene hybrid film consists of a metallic network fully encapsulated between monolayer graphene and quartz-glass substrate. Compared with graphene by itself, the microwave shielding performance of graphene hybrid films improved considerably, owing to increased microwave reflectivity with improved electrical conductivity. Films were characterized through Raman spectroscopy, and optical microscopy. Two type of


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graphene hybrid films, a 320 µm (G/320M) and 160 µm (G/160M), were successfully fabricated using a CVD process atop a metallic network. The Rs values, EMI shielding performance, and optical transmission of graphene hybrid films were evaluated with the van der Pauw method, a vector network analyser, and a spectrophotometer, respectively. 2. EXPERIMENTAL SECTION 2.1 MATERIALS The quartz-glass substrates were obtained from CNBM Kinglass Ltd. (Quzhou, China), and network masks were fabricated by China Electronics Technology Group Corporation (Nanjing, China). Graphene films were produced by Hefei Vigon Material Technology CO., Ltd. 2.2 FABRICATION OF METALLIC NETWORK After cutting the quartz-glass substrates into 4 inch diameter circular wafers, surfaces were wiped clean using a cloth dipped in alcohol. Prior to sputtering, the quartz-glass substrates were washed in a solution of H2SO4 and H2O2 for 10 min at 120 °C. Then a 400−450 nm thick Al layer was sputtered onto the substrates via a Kurt J. Lesker Lab-18 sputtering system at 1000 W for 27.5 min. A 1.1 µm thick photoresist RZJ−304 (25cp viscosity, Suzhou Ruihong Ltd. China) was then spin-coated on the Al film. A network mask prepared by e-beam direct writing was covered on the surface by photoresist and exposed for 5 seconds to a mask aligner (Karl Suss MA/BA6). After being developed by RZX-3038 (Suzhou Ruihong Ltd. China) developer for 50 seconds, the samples were baked at 80 °C for 20 minutes, and then 120 °C for 30 minutes. The uncovered Al film was then removed by etching in a solution of H3PO4: CH3COOH: HNO3 (16: 2: 1) at 40 °C for 170 seconds. Excess photoresist was removed by fuming substrates in HNO3.


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2.3 SYNTHESIS OF GRAPHENE Copper foil (Alfa Aesar, 40 µm thick, 99.8% purity) was placed at the centre of a tube furnace (MTI, OTF-1200x), the foil was heated to the temperature of 1000 °C under H2 at 60 Pa for 30 min. CH4 gas was then introduced into the quartz tube for 2 h. The furnace was then cooled to room temperature under H2 and CH4 mixture gas. Graphene coated copper foils were then removed from the furnace. 2.4 ASSEMBLING OF GRAPHENE HYBRID FILMS Polymethyl methacrylate (PMMA) was used to transfer the graphene from the copper foil to the metallic network. The graphene-covered copper foil was spin-coated with PMMA at 3500 rmp for 1 minute. Following drying the copper substrate was removed in Marble’s etchant (HCl: H2O: CuSO4 = 50 mL: 50 mL: 10 g). Samples were removed from Marble’s etchant and placed in deionized water for 5 minutes. PMMA/graphene films were then stamped onto metallic network and dried. Tweezers and crystallisation dishes were cleaned using a cloth dipped in acetone, and then washed using isopropyl alcohol before the acetone had fully dried. Samples were placed in an acetone bath for ∼2 hour to remove the bulk of the PMMA. Samples were transferred to a new acetone bath and left overnight to remove residual PMMA from the graphene surfaces. Finally, samples were left to rest for 1 h in an isopropyl alcohol bath to remove residual acetone, and then allowed to dry. 2.5 CHARACTERIZATION AND MEASUREMENT Atomic Force Microscope (AFM) was carried out using a Bruker ICON microscope with PFQNE SiN tips in tapping mode. Raman spectroscopy measurements were performed at ambient conditions using a Renishaw InVia RM1000 Raman system with a 514 nm laser at an


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incident Power of 0.22 mW using a 100x objective lens. Visible transmittance was measured with a UV-310PC spectrophotometer (Shimadzu, Japan) at wavelengths of 400−700 nm. The electromagnetic shielding effectiveness was measured in the 26.5−40 GHz (Ka-band) and 12−18 GHz (Ku-band) using an antenna system with an E8363B PNA Vector Network analyzer (Agilent, United States) and transmitter and receiver antennas. The microwave reflection loss (RL) in the Ka-band was measured using the Radar Cross Section measurement method by an E8363B PNA Vector Network analyzer (Agilent, United States). 3. RESULTS AND DISCUSSION 3.1. SYNTHESIS OF HYBRID GRAPHENE FILM Two Al-based metallic network films with periods of 160 and 320 µm (160M and 320M) were combined with graphene films for our two sample types G/160M and G/320M respectively. An illustration of the synthesis process for these hybrid films can be seen in Figure 1.

Figure 1. Synthesis process for graphene hybrid film, using an Al-based metallic network. 3.2. SURFACE MORPHOLOGICAL ANALYSIS


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a

b

c

d

100 µm

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e

f

100 µm

Figure 2. (a & b) Qualitative demonstration of the transparency of G/320M and G/160M laid over a photograph. (c & d) Micrographs of G/320M and G/160M, respectively. (e) AFM image of the graphene hybrid film crossing Al wire. (f) Height profile taken along blue line on AFM image shown in Figure 2e. To show qualitatively the inherent transparent nature of these films two samples were placed atop a photograph which was taken by one of the author Limin Ma. Figure 2a and b present this photograph with the G/320M and G/160M hybrid films. To reveal the surface morphology of the graphene hybrid films, we present both AFM images and optical micrographs shown in Figure 2c-f. Figure 2c, d show that the period of the metallic networks is 320 µm and 160 µm, respectively. In the AFM image of graphene hybrid sample as shown in Figure 2e, the Al wire is visible and a complimentary line scan shown in Figure 2f shows the corresponding height profile


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along the blue line in Figure 2e. By measuring the step height in the line profile, we can obtain that the thickness of Al wire is 400 nm, and the line-width is approximately 3.5 µm. 3.3. RAMAN STUDIES

Figure 3. (a) Raman spectrum of the graphene hybrid film, taken at the section of Al wire, and void substrate, respectively. (b) Raman spectra of the line shown in the inset image for graphene hybrid film. Raman spectra of the graphene hybrid films are shown in Figure 3 and Figure 4. Two prominent peaks G near 1582cm-1 and 2D peaks near 2670cm-1 in both representative spectra in Figure 3a indicating not only successful transfer onto the Al network, but also that the graphene studied is predominantly monolayer because of the intensity of G/2D peak ratio ∼0.5 which is a typical value for monolayer graphene.54,55 The absence of the disorder-related D peak near 1350 cm-1 typify the defect-free for graphene on void quartz-glass with Al wire absence.54,56 Compared with the graphene on void quartz-glass substrate also in Figure 3a, the Raman spectra of graphene on Al wires shows a sloping background due to the photoluminescence of the Al


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network. Additionally, the Al network provides surface enhanced Raman spectroscopy (SERS) data such that the D, G and 2D peaks in Figure 3a can be enhanced.57 The Raman profile

Figure 4. (a) Optical microscopy of the Raman mapping section for graphene hybrid film. (b & c & d) Raman mapping of D, G, and 2D peak respectively for graphene hybrid film. (e & f) Raman mapping of G/2D, and D/G intensity for graphene hybrid film. breakdown of this region in Figure 3b shows how the Raman signal increases in the presence of the Al network. Complementary Raman maps, as shown in Figure 4, show the complete adhesion of graphene onto the Al network. The intensity maps in Figure 4b−d show


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enhancement of graphene peaks D, G, and 2D due to near-field plasmonic effects in the vicinity of Al network.57 According to Figure 4e, the intensity of G/2D shows that the graphene present is monolayer in the void regions of the network. The ratio is slightly higher over the Al network, and this is due to SERS enhancement of each peak not being equal, which is dependent on the Al plasmon frequency distribution. Figure 4f, illustrates a low intensity of the disorder-induced D peak (1455 cm-1) is observed relative to that of the G peak (1598 cm-1) with peak intensity ratios (D/G values) in the range of 0.03 to 0.2 for graphene on Al network. The D peak largely comes from the disorder at the edge of the Al network boundary. The D peak also represents an edge effect, and thus the less pronounced the D peak the less edge effects present and the better the graphene’s coherency to the Al.58 For completeness, the supplementary information contains corresponding Raman maps of the full width at half maximum (FWHM) (Figure S1-S3) and the peak positions (Figure S4-S6). The peaks only broaden slightly in the presence of Al due to a convolution of Raman scattering with the Al luminescence. The sharpness of all peaks shows that the luminescence effect does not severely disturb the Raman assignment. The position shifts of the G and 2D peaks provide information on mechanical strain and doping.54 Compared with graphene on void quartz-glass, graphene on or even near Al wires shows mechanical strain. 3.4. Optical transparency The normalized visible transmittance of the monolayer graphene, metallic network, and graphene hybrid films are plotted in Figure 5. The monolayer graphene exhibits an average visible transmittance of 96.8% at 400−700 nm. This is slightly lower than the reported value of 97.7%,59


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Figure 5. Normalized visible transmittance of monolayer graphene, metallic network, and graphene hybrid films. this discrepancy is accounted for by the 5 µm thick PMMA layer covering on graphene sheet. It was necessary to leave the PMMA layer intact until Raman and microwave measurements were completed to protect the graphene from damage during testing. The measured average visible transmittance of samples 160M and 320M were 95.0%, and 97.8%, respectively without added graphene. The graphene/PMMA sheet introduced an expected 3.0−4.9% loss of visible transmittance when compared to the corresponding unaltered metal network. Thus, the average visible transmittance of the combined graphene hybrid films G/160M and G/320M was 91.0% and 94.0%, respectively. 3.5. Conductive properties and electromagnetic shielding performance The sheet resistance of the monolayer graphene, metallic network and graphene hybrid films were measured by van der Pauw method.60 The reported values are based on an average of 10


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measurements for each sample. The sheet resistance of our CVD monolayer graphene is as high as 813.27 Ω/sq. After integration with the Al network, the sheet resistance decreased to an average of 5.53 Ω/sq and 20.67 Ω/sq for G/160M and G/320M, respectively. This can be compared to the sheet resistance of the Al network samples without graphene 160M and 320M with values of 4.66 Ω/sq and 18.75 Ω/sq respectively. The sheet resistance of graphene hybrid films slightly increased from that of Al network, which may be caused by some corrosion and oxidation of the Al network during the graphene transfer process.49 The electromagnetic SE is always used for evaluating shielding performance, and is defined as SE (dB) = -10 log (Pi/P0)

(1)

Among which Pi, P0 is the incident power and transmitted power, respectively. The SE measurement was carried out using an antenna system at Ku-band (12−18 GHz) and Ka-band (26.5−40 GHz). Figure 6a and b show that after integrating graphene with the metallic networks

Figure 6. SE of monolayer graphene, metal network, and graphene hybrid films (a) at 12-18 GHz, and (b) 26.5-40 GHz.


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Table 1. Electromagnetic shielding and visible transmittance for different EMI shielding materials.

EMI shielding material

Frequency/GHz

SE/dB

Visible transmittance

Ref.

Silver nanowires

8−12

12.5−16

80%

13

Monolayer graphene

2.2−7

2.27

97%

24

RGO/PEI films

0.5−8.5

6.37

62%

29

Graphene network

10

12.86

70.85%

30

A few layers of epitaxial graphene

12−18

15

70%

32

Triangular ring mesh

12−18

17−21

95%

61

Metal mesh prepared by electrohydrodynamic jet printing

8−12

20

88.2%

62

Graphene hybrid film G/320M

26.5−40

8.09−8.53

94%

Present work


26.5−40

13.48−14.52

91%

Present work


12−18

16.36−20.86

94%

Present work


12−18

23.60−28.91

91%

Present work

the microwave SE of the graphene hybrid films is higher than both graphene and metallic network apart. The SE enhancement is more dramatic when comparing the hybrid films against the pristine monolayer graphene and is presented in Figure 6. The SE of the graphene

hybrid

film G/160M sees an increase from 3.46 dB to 28.91 dB, a shift of 25.45 dB (99.7% energy attenuation) at 12 GHz. Similar behaviour is observed at 26.5 GHz with an increase from 3.46 dB to 14.52 dB, a shift of 11.06 dB (92.17% energy attenuation). These experimental results indicate that the SE of a monolayer graphene can be significantly enhanced through integration with an Al network. Thus, results indicate that the graphene hybrid films can yield an SE > 23.60 dB with visible transmittance of 91%, or an SE > 16.36 dB with visible transmittance of 94% at 12-18 GHz, which are comparable with the performance of other transparent EMI shielding materials listed in Table 1. As shown in Figure 6a and 6b, the SE of metallic network decreased as the frequency increased. While the SE of graphene is about 3.46 dB at both Ku-band and Ka-band, which did


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not change much as the frequency increased. Since both the SE curves of metallic network and graphene are smooth and can be extrapolated from Ku-band to Ka-band, or from Ka-band to Ku-band, surely the SE of graphene and metallic network hybrid film can be extrapolated to each other by carefully calculation.

As the shielding mechanism is an important aspect for an EMI shielding material,61 we also measured the reflection loss (RL) at 26.5-40 GHz of G/160M using a Radar-Cross-Section (RCS) measurement system in a microwave chamber. The corresponding result is shown in Figure 7a. Here, RL > -1.18 dB is observed across the range of 26.5 to 40 GHz. The relationship between RL and reflectance (R) can be written as RL (dB) = −10 log10 |R|

(2)

In addition, the transmittance (T) and absorbance (A) can be calculated by SE (dB) = −10 log10 |T|

(3)

A+R+T=1

(4)

Figure 7. (a) The reflection loss, and (b) reflectance, transmittance and absorbance of graphene hybrid film G/160M at 26.5-40 GHz.


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As shown in Fig. 7b, the reflectance > 76.3%, while the absorbance < 19.2% for G/160M in the range of 26.5-40 GHz. It can be seen here that reflection component is the major shielding mechanism which occupies most of the energy attenuation in this band. This can be compared with pristine monolayer graphene as shown in Fig. S7 and S8. For the graphene hybrid films, the microwave reflectance is significantly enhanced, the absorbance is partially reduced, and the transmittance is reduced all which lead to an improved SE value. The work presented here provides evidence through this improved SE value to the validity and utility of a graphene metallic network hybrid film. From a methodology stand point, our data suggests these hybrid films could become the foundation of future studies and frameworks to help bring graphene shielding materials to the forefront of the field. It should be pointed out that, if another metal with comparable conductive properties were used to make the metallic network, such as gold or copper,49 and silver,41 then the sheet resistance could be further reduced and the SE could be further improved. Besides, we can see that better shielding performance of metallic network leads to better shielding performance of graphene hybrid film. Decreasing the period, increasing the thickness and line-width of the metallic network could reduce the sheet resistance and improve the SE further more. However, decreasing the period and increasing the line-width of metallic network would reduce the optical transmittance. While increasing the thickness of metallic network would not impact the optical transmittance that much. The shape of network is also an important factor to determine the shielding performance. Changing the shape of metallic network from grid to ring with same period and line-width would improve the SE by 2 dB at 12-18 GHz,63 the effect of network shape for

graphene hybrid film will be discussed in detail in our future work. The graphene hybrid film not only provides a continuous conducting film that metallic network cannot, but also provides


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strong electromagnetic SE that monolayer graphene cannot provide. Thus, these two materials form a composite or hybrid film that opens up new possibilities and opportunities to the electromagnetic shielding field. There may also be additional surface effects from the graphene that contribute to an overall increase in corrosion and damage resistance to the underlying metallic network. Comparing with the graphene/metallic mesh/transparent dielectric (GMTD) hybrid structures we published before,43 the hybrid films in this work are completely different. First, for GMTD the transparent dielectric is presented between graphene and metallic mesh to separate them from each other, making it an interleaved structure. The transparent dielectric is necessary and cannot be replaced by conductive materials. Besides, the thickness of dielectric can strongly affect the EMI shielding performance of this multi-layer structure. While in this work we are focusing on a graphene hybrid film which graphene was directly transferred onto the surface of metallic network. The substrate here is only to support the graphene and metallic network film, which kind of material and the thickness of substrate are not to matter. Second, GMTD are non-conducting multi-layer structure as a whole; while the hybrid films in this work are very good conductors; this difference leads to different applications. Third, for GMTD hybrid structure, the microwave shielding mechanism is combined absorption and reflection, in some cases absorption is the main microwave shielding mechanism. While here for the graphene hybrid films, reflection is the main microwave shielding mechanism, and absorption is not much. Fourth, for the GMTD hybrid structure, each layer of graphene film or metallic film are independent, and it is hard to characterize the GMTD hybrid structure as a whole except for measuring microwave shielding and optical transmitting performance. While in this work for graphene hybrid films, graphene and metallic network fit closely to form one film. So we can characterize the hybrid film as a whole using Raman, optical imaging and AFM.


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CONCLUSION In conclusion, the integration of graphene and metallic network into graphene hybrid films were fabricated and tested here to highlight their potential for both high conductivity and EMI shielding effects. These fabricated films possessed comparable optical transparency and electrical properties to existing ITO films currently being used for shielding. Our work followed two types of graphene hybrid films from fabrication, spin coating, patterning and through to characterization. Our first hybrid film, G/160M, exhibited 91% optical transmittance, 5.53 Ω/sq sheet resistance, and maximum SE of 28.91 dB at 12 GHz. Similar behaviour was seen in G/320 with 94% optical transmittance, 20.67 Ω/sq and a maximum SE of 20.86 dB at 12 GHz. In both cases, films showed superior properties when the metallic network and graphene were combine versus their independent behaviour. The significant enhancement of EMI shielding performance compared with pristine graphene was shown to be due to the increased microwave reflection with lower sheet resistance provided by the underlying metallic network. This study offers a new strategy for transparent EMI shielding, and provides a viable option for exploration outside of standard ITO shielding films. ASSOCIATED CONTENT Supporting Information. Additional figures (PDF). This material is available free of charge via the Internet at http://pubs.acs.org. AUTHOR INFORMATION Corresponding Author *Tel.: +86 0451 86412041-803. Fax: +86 0451 86402258. E-mail: [email protected].


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Notes The authors declare no competing financial interest. ACKNOWLEDGEMENTS This work was financially supported by the National Natural Science Foundation of China (NSFC) (Grant No. 61575075), the Fundamental Research Funds for the Central Universities (Grant No. HIT.NSRIF.2014020), Natural Science Foundation of Heilongjiang Province (Grant No. F2016014), the Postdoctoral Science-Research Development Foundation of Heilongjiang Province (Grant No. LBH-Q13078). Ling Hao wishes to acknowledge the UK NMS programme for funding, and Limin Ma for her studying at NPL funded by the China Scholarship Council (CSC). The authors would like to thank T. Li for fabrication of metallic network samples, and J. Sun for facilitating the visible transmittance measurements. REFERENCES 1) Andrews, R. W.; Peterson, R. W.; Purdy, T. P.; Cicak, K.; Simmonds, R. W.; Regal, C. A.; Lehnert, K. W. Bidirectional and Efficient Conversion between Microwave and Optical Light. Nature Phys., 2014, 10, 321−326. 2) Palomaki, T. A.; Harlow, J. W.; Teufel, J. D.; Simmonds R. W.; Lehnert, K. W. Coherent State Transfer between Itinerant Microwave Fields and A Mechanical Oscillator. Nature, 2013, 495, 210−214. 3) Singh, V.; Bosman, S. J.; Schneider, B. H.; Blanter, Y. M.; Castellanos-Gomez, A.; Steele, G. A. Optomechanical Coupling Between A Multilayer Graphene Mechanical Resonator and A Superconducting Microwave Cavity. Nature Nanotech., 2014, 9, 820−824.


19


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 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 28

4) Kumar, A.; Singh, A. P.; Kumari, S.; Srivastava, A. K.; Bathula, S.; Dhawan, S. K.; Dutta, P. K.; Dhar, A. EM Shielding Effectiveness of Pd-CNT-Cu Nanocomposite Buckypaper. J. Mater. Chem. A, 2015, 3, 13986−13993. 5) Ameli, A.; Nofar, M.; Wang, S.; Park, C. B. Lightweight Polypropylene/StainlessSteel Fiber Composite Foams with Low Percolation for Efficient Electromagnetic Interference Shielding. ACS Appl. Mater. Interfaces, 2014, 6, 11091−11100. 6) Song, W. L.; Guan, X. T.; Fan, L. Z.; Cao, W. Q.; Wang, C. Y.; Zhao, Q. L.; Cao, M. S. Magnetic and Conductive Graphene Papers Toward Thin Layers of Effective Electromagnetic Shielding. J. Mater. Chem. A, 2015, 3, 2097−2107. 7) Umrao, S.; Gupta, T. K.; Kumar, S.; Singh, V. K.; Sultania, M. K.; Jung, J. H.; Oh, I.-K.; Srivastava, A. Microwave-assisted Synthesis of Boron and Nitrogen Co-Doped Reduced Graphene Oxide for the Protection of Electromagnetic Radiation in KuBand. ACS Appl. Mater. Interfaces, 2015, 7, 19831−19842.. 8) Shen, B.; Zhai, W.; Zheng, W. Ultrathin Flexible Graphene Film: An Excellent Thermal Conducting Material with Efficient EMI Shielding. Adv. Funct. Mater., 2014, 24, 4542−4548. 9) Wen, B.; Cao, M.; Lu, M.; Cao, W.; Shi, H.; Liu, J.; Wang, X.; Jin, H.; Fang, X.; Yuan, J. Reduced Graphene Oxides: Light ‐ Weight and High-Efficiency Electromagnetic Interference Shielding at Elevated Temperatures. Adv. Mater., 2014, 26, 3484−3489. 10) Mural, P. K. S.; Pawar, S. P.; Jayanthi, S.; Madras, G.; Sood, A. K.; Bose, S. Engineering Nanostructures by Decorating Magnetic Nanoparticles onto Graphene


20

Page 21 of 28

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 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Oxide Sheets to Shield Electromagnetic Radiations. ACS Appl. Mater. Interfaces, 2015, 7, 16266−16278. 11) Lu, Z.; Liu, Y.; Wang, H.; Zhang, Y.; Tan, J. Optically Transparent Frequency Selective Surface Based on Nested Ring Metallic Mesh. Opt. Express, 2016, 24, 26109−26118. 12) Maniyara, R. A.; Mkhitaryan, V. K.; Chen, T. L.; Ghosh, D. S.; Pruneri, V. An Antireflection Transparent Conductor with Ultralow Optical Loss (< 2%) and Electrical Resistance (< 6 Ω sq−1). Nat. Commun., 2016, 7, 13771. 13) Hu, M.; Gao, J.; Dong, Y.; Li, K.; Shan, G.; Yang, S.; Li, R. K. Y. Flexible Transparent PES/Silver Nanowires/PET Sandwich-Structured Film for HighEfficiency Electromagnetic Interference Shielding. Langmuir, 2012, 28, 7101−7106. 14) Batrakov, K.; Kuzhir, P.; Maksimenko, S.; Paddubskaya, A.; Voronovich, S.; Lambin, P.; Kaplas, T.; Svirko, Y. Flexible Transparent Graphene/Polymer Multilayers for Efficient Electromagnetic Field Absorption. Sci. Rep., 2014, 4, 7191. 15) Lu, Z.; Wang, H.; Tan, J.; Ma, L.; Lin, S. Achieving an Ultra-Uniform Diffraction Pattern of Stray Light with Metallic Meshes by Using Ring and Sub-Ring Arrays. Opt. Lett., 2016, 41, 1941−1944. 16) Kim, B. R.; Lee, H. K.; Kim, E.; Lee, S. H. Intrinsic Electromagnetic Radiation Shielding/Absorbing Characteristics of Polyaniline-Coated Transparent Thin Films. Synthetic Met., 2010, 160, 1838−1842. 17) Kang, J.; Kim, D.; Kim, Y.; Choi, J. B.; Hong, B. H.; Kim, S. W. High-Performance Near-Field Electromagnetic Wave Attenuation in Ultra-Thin and Transparent Graphene Films. 2D Mater., 2017, 4, 025003.


21


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 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 28

18) Xu, H.; Anlage, S. M.; Hu, L.; Gruner, G. Microwave Shielding of Transparent and Conducting Single-Walled Carbon Nanotube Films. Appl. Phys. Lett., 2007, 90, 183119. 19) Pawar, S. P.; Marathe, D. A.; Pattabhi, K.; Bose, S. Electromagnetic Interference Shielding Through MWNT Grafted Fe3O4 Nanoparticles in PC/SAN Blends. J. Mater. Chem. A, 2015, 3, 656. 20) Gupta, T. K.; Singh, B. P.; Mathur, R. B.; Dhakate, S. R. Multi-Walled Carbon Nanotube–Graphene–Polyaniline

Multiphase

Nanocomposite

with

Superior

Electromagnetic Shielding Effectiveness. Nanoscale, 2014, 6, 842−851. 21) Rohini, R.; Bose, S. Electromagnetic Interference Shielding Materials Derived from Gelation of Multiwall Carbon Nanotubes in Polystyrene/Poly (Methyl Methacrylate) Blends. ACS Appl. Mater. Interfaces, 2014, 6, 11302−11310. 22) Qiang, R.; Du, Y.; Zhao, H.; Wang, Y.; Tian, C.; Li, Z.; Han, X.; Xu, P. Metal Organic Framework-Derived Fe/C Nanocubes Toward Efficient Microwave Absorption. J. Mater. Chem. A, 2015, 3, 13426−13434. 23) Yousefi, N.; Sun, X.; Lin, X.; Shen, X.; Jia, J.; Zhang, B.; Tang, B.; Chan, J. M.; Kim, J. K. Highly Aligned Graphene/Polymer Nanocomposites with Excellent Dielectric Properties for High-Performance Electromagnetic Interference Shielding. Adv. Mater., 2014, 26, 5480−5487. 24) Wu, H.; Kong, D.; Ruan, Z.; Hsu, P. C.; Wang, S.; Yu, Z.; Carney, T. J.; Hu, L.; Fan, S.; Cui, Y. A Transparent Electrode Based on A Metal Nanotrough Network. Nature Nanotech., 2013, 8, 421−425.


22

Page 23 of 28

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 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


25) Tung, V. C.; Chen, L. M.; Allen, M. J.; Wassei, J. K.; Nelson, K.; Kaner, R. B.; Yang, Y. Low-Temperature Solution Processing of Graphene-Carbon Nanotube Hybrid Materials for High-Performance Transparent Conductors. Nano lett., 2009, 9, 1949−1955. 26) Bae, S.; Kim, H.; Lee, Y.; Xu, X.; Park, J. S.; Zheng, Y.; Balakrishnan, J.; Lei, T.; Kim, H. R.; Song, Y. I.; Kim, Y.-J.; Kim, K. S.; Ozyilmaz, B.; Ahn, J.-H.; Hong, B. H.; Kim, Y. J. Nanopores: Graphene Opens Up to DNA. Nature Nanotech., 2010, 5, 574−698. 27) Kim, K. S.; Zhao, Y.; Jang, H.; Lee, S. Y.; Kim, J. M.; Kim, K. S.; Ahn, J.-H.; Kim, P.; Choi, J.-Y.; Hong, B. H. Large-Scale Pattern Growth of Graphene Films for Stretchable Transparent Electrodes. Nature, 2009, 457, 706−710. 28) Hecht, D. S.; Hu, L.; Irvin, G. Emerging Transparent Electrodes Based on Thin Films of Carbon Nanotubes, Graphene, and Metallic Nanostructures. Adv. Mater., 2011, 23, 1482−1513. 29) Gao, T.; Li, Z.; Huang, P. S.; Shenoy, G. J.; Parobek, D.; Tan, S.; Lee, J.; Liu, H.; Leu, P. W. Hierarchical Graphene/Metal Grid Structures for Stable, Flexible Transparent Conductors. ACS Nano, 2015, 9, 5440−5446. 30) Hong, S. K.; Kim, K. Y.; Kim, T. Y.; Kim, J. H.; Park, S. W.; Kim, J. H.; Cho, B. J. Electromagnetic Interference Shielding Effectiveness of Monolayer Graphene. Nanotechnol., 2012, 23, 455704. 31) Barbosa, G. M.; Mosso, M. M.; Vilani, C.; Larrudé, D. R.; Romani, E. C.; Junior, F. L. Graphene Microwave Absorber: Transparent, Lightweight, Flexible, and CostEffective. Microw. Opt. Techn. Let., 2014, 56, 560−563.


23


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 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 24 of 28

32) Wen, B.; Wang, X. X.; Cao, W. Q.; Shi, H. L.; Lu, M. M.; Wang, G.; Jin, H. B.; Wang, W. Z.; Yuan, J.; Cao, M. S. Reduced Graphene Oxides: the Thinnest And Most Lightweight Materials with Highly Efficient Microwave Attenuation Performances of the Carbon World. Nanoscale, 2014, 6, 5754−5761. 33) Mishra, M.; Singh, A. P.; Singh, B. P.; Singh, V. N.; Dhawan, S. K. Conducting Ferrofluid: A High-Performance Microwave Shielding Material. J. Mater. Chem. A, 2014, 2, 13159−13168. 34) Batrakov, K.; Kuzhir, P.; Maksimenko, S.; Paddubskaya, A.; Voronovich, S.; Kaplas T.; Svirko, Y. Enhanced Microwave Shielding Effectiveness of Ultrathin Pyrolytic Carbon Films. Appl. Phys. Lett, 2013, 103, 073117. 35) Kim, S.; Oh, J.-S.; Kim, M.-G.; Jang, W.; Wang, M.; Kim, Y.; Seo, H.W.; Kim, Y.C.; Lee, J.-H.; Lee, Y.; Nam, J.-D. Electromagnetic Interference (EMI) Transparent Shielding of Reduced Graphene Oxide (RGO) Interleaved Structure Fabricated by Electrophoretic Deposition. ACS Appl. Mater. Interfaces, 2014, 6, 17647−17653. 36) Han, J.; Wang, X.; Qiu, Y.; Zhu, J.; Hu, P. Infrared-Transparent Films Based on Conductive Graphene Network Fabrics for Electromagnetic Shielding. Carbon, 2015, 87, 206−214. 37) Lu, Z.; Ma, L.; Tan, J.; Wang, H.; Ding, X. Transparent Multi-Layer Graphene/Polyethylene

Terephthalate

Structures

with

Excellent

Microwave

Absorption and Electromagnetic Interference Shielding Performance. Nanoscale, 2016, 8 16684−16693.


24

Page 25 of 28

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 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


38) Moon, J. S.; Gaskill, D. K. Graphene: Its Fundamentals to Future Applications. IEEE T. Microw. Theory, 2011, 59, 2702−2708. 39) Lobet, M.; Reckinger, N.; Henrard, L.; Lambin, P. Robust Electromagnetic Absorption by Graphene/Polymer Heterostructures. Nanotechnology, 2014, 26, 285702. 40) Li, S.; Duan, Q.; Li, S.; Yin, Q.; Lu, W.; Li, L.; Gu, B.; Hou, B.; Wen, W. Perfect Electromagnetic Absorption at One-Atom-Thick Scale. Appl. Phys. Lett., 2015, 107, 181112. 41) Wu, B.; Tuncer, H. M.; Naeem, M.; Yang, B.; Cole, M. T.; Milne, W. I.; Hao, Y. Experimental Demonstration of A Transparent Graphene Millimetre Wave Absorber with 28% Fractional Bandwidth at 140 GHz. Sci. Rep., 2014, 4, 4130. 42) Bludov, Y. V.; Peres, N. M.; Vasilevskiy, M. I. Unusual Reflection of Electromagnetic Radiation from A Stack of Graphene Layers at Oblique Incidence. J. Optics, 2013, 15, 114004. 43) Lu, Z.; Ma, L.; Tan, J.; Wang, H.; Ding, X. Graphene, Microscale Metallic Mesh, and

Transparent

Dielectric

Hybrid

Structure

for

Excellent

Transparent

Electromagnetic Interference Shielding and Absorbing. 2D Mater., 2017, 4, 025021. 44) Pearce, R.; Tan, X.; Wang, R.; Patel, T.; Gallop, J.; Pollard, A.; Yakimova, R.; Hao, L. Investigations of the effect of SiC growth face on graphene thickness uniformity and electronic properties, Surf. Topogr.: Metrol. Prop., 2014, 3, 015001. 45) Hao, L.; Gallop, J.; Goniszewski, S.; Shaforost, O.; Klein, N.; Yakimova, R. NonContact Method for Measurement of the Microwave Conductivity of Graphene. Appl. Phys. Lett, 2013, 103, 123103.


25


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 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 28

46) Kim, K. K.; Reina, A.; Shi, Y.; Park, H.; Li, L.-J.; Lee, Y. H.; Kong, J. Enhancing the Conductivity of Transparent Graphene Films Via Doping. Nanotechnology, 2010, 21, 285205. 47) De, S.; Coleman, J. N. Are There Fundamental Limitations on the Sheet Resistance and Transmittance of Thin Graphene Films. ACS Nano, 2010, 4, 2713−2720. 48) Blake, P.; Brimicombe, P. D.; Nair, R. R.; Booth, T. J.; Jiang, D.; Schedin, F.; Ponomarenko, L. A.; Morozov, S. V.; Gleeson, H. F.; Hill, E. W.; Geim A. K.; Novoselov, K. S. Graphene-Based Liquid Crystal Device. Nano Lett., 2008, 8, 1704−1708. 49) Zhu, Y.; Sun, Z.; Yan, Z.; Jin, Z.; Tour, J. M. Rational Design of Hybrid Graphene Films for High-Performance Transparent Electrodes. ACS nano, 2011, 5, 6472−6479. 50) Xue, D. J.; Xin, S.; Yan, Y.; Jiang, K. C.; Yin, Y. X.; Guo, Y. G.; Wan, L. J. Improving the Electrode Performance of Ge Through Ge@C Core–Shell Nanoparticles and Graphene Networks. J. Am. Chem. Soc., 2012, 134, 2512−2515. 51) Bult, J. B.; Crisp, R.; Perkins, C. L.; Blackburn, J. L. Role of Dopants in LongRange Charge Carrier Transport for p-Type and n-Type Graphene Transparent Conducting Thin Films. ACS nano, 2013, 7, 7251−7261. 52) Deng, B.; Hsu, P. C.; Chen, G.; Chandrashekar, B. N.; Liao, L.; Ayitimuda, Z.; Wu, J.; Guo, Y.; Lin, L.; Zhou, Y.; Aisijiang, M.; Xie, Q.; Cui, Y.; Liu, Z.; Aisijiang, M. Roll-to-roll Encapsulation of Metal Nanowires Between Graphene and Plastic Substrate for High-Performance Flexible Transparent Electrodes. Nano letters, 2015, 15, 4206−4213.


26

Page 27 of 28

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 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


53) Ahn, Y.; Jeong, Y.; Lee, D.; Lee, Y. Copper Nanowire–Graphene Core–Shell Nanostructure for Highly Stable Transparent Conducting Electrodes. ACS nano, 2015, 9, 3125−3133. 54) Lee, J. E.; Ahn, G.; Shim, J.; Lee, Y. S.; Ryu, S. Optical Separation of Mechanical Strain from Charge Doping in Graphene. Nat. Commun., 2012, 3, 1024. 55) Wang, Y. Y.; Ni, Z. H.; Yu, T.; Shen, Z. X.; Wang, H. M.; Wu, Y. H.; Chen, W.; Shen A. T. Wee, Transferring and Identification of Single- and Few-Layer Graphene on Arbitrary Substrates. J. Mater. Chem. C, 2008, 112, 10637−10640. 56) Ferrari, A. C.; Basko, D. M. Raman Spectroscopy as A Versatile Tool for Studying the Properties of Graphene. Nature Nanotech., 2013, 8, 235−246. 57) Schedin, F.; Lidorikis, E.; Lombardo, A.; Kravets, V. G.; Geim, A. K.; Grigorenko, A. N.; Novoselov, K. S.; Ferrari, A. C. Surface-Enhanced Raman Spectroscopy of Graphene. ACS nano, 2010, 4, 5617−5626. 58) Malard, L. M.; Pimenta, M. A. A.; Dresselhaus, G.; Dresselhaus, M. S. Raman Spectroscopy in Graphene. Phys.Rep., 2009, 473, 51−87. 59) Nair, R. R.; Blake, P.; Grigorenko, A. N.; Novoselov, K. S.; Booth, T. J.; Stauber, T.; Peres, N. M. R.; Geim, A. K. Fine Structure Constant Defines Visual Transparency of Graphene. Science, 2008, 320, 1308. 60) Van der Pauw, L. J. A Method of Measuring the Resistivity and Hall Coefficient on Lamellae of Arbitrary Shape. Philips Res. Repts., 1958, 13, 220−224. 61) Wang, H.; Lu, Z.; Tan, J. Generation of Uniform Diffraction Pattern and High EMI Shielding Performance by Metallic Mesh Composed of Ring and Rotated Sub-Ring Arrays. Opt. Express, 2016, 24, 22989−23000.


27


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 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 28 of 28

62) Vishwanath, S. K.; Kim, D. G.; Kim, J. Electromagnetic Interference Shielding Effectiveness of Invisible Metal-Mesh Prepared by Electrohydrodynamic Jet Printing. Jpn. J. Appl. Phys., 2014, 53, 05HB11. 63) Tan, J.; , Z. Contiguous metallic rings: an inductive mesh with high transmissivity, strong electromagnetic shielding, and uniformly distributed stray light. Opt. Express, 2007, 15: 790-796.


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