Fabrication of graphene on atomically flat diamond (111) surfaces using nickel as a catalyst

Accepted Manuscript Fabrication of graphene on atomically flat diamond (111) surfaces using nickel as a catalyst

Shohei Kanada, Masatsugu Nagai, Shinya Ito, Tsubasa Matsumoto, Masahiko Ogura, Daisuke Takeuchi, Satoshi Yamasaki, Takao Inokuma, Norio Tokuda PII: DOI: Reference:

S0925-9635(16)30675-6 doi: 10.1016/j.diamond.2017.02.014 DIAMAT 6823

To appear in:

Diamond & Related Materials

Received date: Revised date: Accepted date:

29 November 2016 1 February 2017 15 February 2017

Please cite this article as: Shohei Kanada, Masatsugu Nagai, Shinya Ito, Tsubasa Matsumoto, Masahiko Ogura, Daisuke Takeuchi, Satoshi Yamasaki, Takao Inokuma, Norio Tokuda , Fabrication of graphene on atomically flat diamond (111) surfaces using nickel as a catalyst. The address for the corresponding author was captured as affiliation for all authors. Please check if appropriate. Diamat(2016), doi: 10.1016/ j.diamond.2017.02.014

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Fabrication of graphene on atomically flat diamond (111) surfaces using nickel as a catalyst

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Shohei Kanadaa, Masatsugu Nagaia, Shinya Itoa, Tsubasa Matsumotoa, Masahiko Ogurab,

Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa,

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Daisuke Takeuchib, Satoshi Yamasakib, Takao Inokumaa, and Norio Tokudaa*

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Ishikawa 920-1192, Japan

Energy Technology Research Institute, National Institute of Advanced Industrial

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Science and Technology (AIST), Tsukuba, Ibaraki 305-8568, Japan

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*Corresponding author. E-mail: [email protected] (Norio Tokuda)

Abstract

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KEYWORDS: Graphene, Diamond, Solid-solution reaction, Atomically flat surface

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We fabricated graphene on atomically flat diamond (111) surfaces via annealing with nickel as a catalyst. The annealing was conducted at 900°C for 1 min under Ar atmosphere. Using Raman spectroscopy, the formed graphene was characterized as multilayer with some monolayer coverage. After the graphene layers were removed, the diamond (111) surfaces exhibited step-terrace structures with a root-mean-square roughness of 0.05 nm in the terrace region. The step height was ~0.21 nm, which agreed 1

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well with a single bi-atomic layer of (111) diamond. These results indicate that the graphene layers were formed on atomically flat diamond (111) surfaces with step-terrace structures. The graphene layers showed P-type conduction with sheet

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carrier concentration and mobility values of 5.7×1013 cm−2 and 140 cm2/Vs, respectively.

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These electrical properties are equivalent to the band structure properties predicted by

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density functional theory calculations.

1. Introduction

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Graphene has attracted considerable interest because of its outstanding properties such as high carrier mobility, saturation velocity, thermal conductivity, and

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current-carrying capacity [1–8]. These extraordinary performances originate from the unique band structure called the Dirac cone, which is a linear band near the K point of

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the Brillouin zone [9]. To maximize the performance of graphene, it is necessary to select suitable substrates because graphene is a two-dimensional (2-D) material that is

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affected by the impurities, surface charge, and surface roughness of the substrate [10–

SiO2 and SiC are often used as substrates for graphene. However, diamond is a more desirable substrate for graphene because it is an allotrope of graphene, has small lattice mismatch with graphene, and exhibits low surface charge. In addition, density functional theory calculations have shown that graphene on a diamond (111) surface has 2

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semiconductor-like properties with band gap opening and P/N-type conduction control depending on the termination of the diamond (111) surface [14–16]. Accordingly, graphene-on-diamond structures have attracted considerable attention [17–22]. A

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graphene field-effect transistor on diamond has shown a high cut-off frequency of 155

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GHz [14] and a large current-carrying capacity of 1.8×109 A/cm2 [6]. However, the

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graphene layers have been prepared by exfoliation from bulk, highly oriented pyrolytic

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graphite using the transfer method. This method is unsuitable for mass production. Therefore, simple and stable methods for the formation of graphene-on-diamond

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structures are needed.

Methods of graphene formation using metal catalysts, such as Cu, Ni, and Fe,

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are well known [23–27]. Among them, the direct formation methods of graphene on substrates have attracted the most attention [18,28–30]. For the direct formation of

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graphene on diamond using Cu as catalyst [30], the mobility of graphene on diamond (100) reached 670 cm2/Vs. In contrast, the mobility of graphene on diamond (111) was

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12 cm2/Vs, which is much lower than that on diamond (100). We considered graphene on diamond (111) to have more potential because the lattice mismatch between graphene and diamond (111) is smaller than that between graphene and diamond (100). Therefore, we focused on the formation of high-quality graphene on diamond (111) using metal catalysts. Substrate surface roughness is an important factor in graphene performance. Previous work revealed that diamond is anisotropically etched via a 3

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solid-solution reaction of carbon and nickel with the diamond (111) plane as the stop layer [31]. Using this technique, we fabricated high-quality graphene on atomically flat

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diamond (111) surfaces in this study.

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2. Experimental

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High-pressure, high-temperature synthetic single-crystal diamond (111)

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substrates were used. Each substrate was immersed in an acid mixture of H2SO4/HNO3 (3:1) at 220°C for 15 min to remove surface contaminants. To eliminate damage

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sustained during polishing, the diamond surfaces were anisotropically etched by hydrogen plasma in a microwave plasma enhanced chemical vapor deposition

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(MPECVD) reactor. Subsequently, the substrate surfaces were terminated by oxygen atoms via immersion in an acid mixture of H2SO4/HNO3 (3:1) at 220°C for 15 min.

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Next, nickel films with thicknesses of ~300 nm were deposited onto the diamond (111) substrates using a vacuum evaporation method through a metal mask. To form graphene

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layers using the catalytic effect of the nickel, the samples were annealed using rapid thermal annealing system at 900°C for 1 min under Ar atmosphere. The cooling rate was 10°C/s. Subsequently, graphene-on-diamond structures were fabricated by removing the nickel films using immersion in diluted nitric acid. After characterizing the graphene-on-diamond structures, the graphene layers were removed by immersion in an acid mixture of H2SO4/HNO3 (3:1) at 220°C for 15 min to observe the diamond 4

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surfaces. The samples were characterized by Raman spectroscopy (JASCO, NRS-4100) with an excitation laser wavelength of 532 nm and a spot size of approximately 1 µm. The surfaces of graphene and diamond were observed by atomic force microscopy

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(AFM; Shimadzu, SPM-9700) in dynamic and contact modes, respectively. The

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electrical properties of the formed graphene layers were investigated by Hall effect

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measurements using a van der Pauw contact configuration at room temperature, as

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shown in Fig. 1.

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Fig. 1. Optical microscope image of the fabricated graphene on diamond (111) and the arrangement of Au electrodes for Hall effect measurements.

3. Results and discussion Figure 2(a) shows the AFM image of the samples after the removal of the nickel film. The surface had many rides as well as graphene formed on SiC and diamond [32, 33]. The surface roughness except at the ridges and grain boundaries was 2 nm, as shown in Fig. 2(b). Additionally, the root-mean-square (RMS) roughness 5

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except grain boundary was 0.7 nm. These roughnesses were lower than that of high-quality graphene on ultrananocrystalline diamond, as reported in [33].

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(a)

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Fig. 2. (a) AFM image of the graphene formed on diamond (111) and (b) cross-sectional image along the white line (A–B) in (a).

Figures 3(a), 3(b), and 3(c) show the Raman spectra of the graphene samples formed on diamond (111), a 2-D Raman map showing the ratio of the intensity of the

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2D peak to that of the G peak (I2D/IG), and the histogram of the 2-D Raman mapping of I2D/IG, respectively. For the Raman spectra in Fig. 3(a), the peaks at approximately 1333 cm−1, 1580 cm−1 (G band), and 2700 cm−1 (2D band) indicate that graphene layers were

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successfully formed on diamond. The I2D/IG ratios indicate that graphene comprised a

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monolayer, a disoriented bilayer (I2D/IG ≥ 2), and an A-B stacked bilayer (I2D/IG = 1) [34,

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35]. Therefore, the layer number of graphene was nonuniform. As shown in Figs. 3(b)

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and 3(c), 75% of the area in which graphene was formed had three or more layers of graphene. The coverage ratio of the monolayer and bilayer graphene to the diamond

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surface area was estimated to be 25%. These results clearly indicate that multilayer graphene was dominant in this study.

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(c)

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Fig. 3. (a) Typical Raman spectra for one (monolayer), two (bilayer), and three or more layers of graphene on diamond (111). (b) 2-D Raman mapping for the ratio of the intensity of the 2D peak to that of the G peak (I2D/IG). (c) Histogram of the Raman 2-D mapping of I2D/IG.

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Figure 4(a) shows an AFM image of the diamond surface after the removal of the graphene, and Fig. 4(b) shows the cross-sectional height profile along the white line (A–B) in Fig. 4(a). These figures clearly show that the diamond surface exhibited a step-terrace structure with a RMS roughness of 0.05 nm in the terrace region. The step height was ~0.21 nm, which is in good agreement with the layer height of single bi-atomic (111) diamond. The results indicate that graphene was successfully deposited

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on atomically flat diamond (111) surfaces by the solid-solution reaction of carbon with

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nickel.

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Fig. 4. (a) AFM image of the diamond surface after graphene removal. (b) Cross-sectional image along the white line (A–B) in (a). 9

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Figures 5 and 6 show the AFM images of the diamond surface before and after etching by the solid-solution reaction of carbon with nickel, respectively, along with

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their corresponding height profiles. As shown in Fig. 5, triangular pits with a density of

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106 cm−2 were formed during hydrogen-plasma etching because the diamond surface

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had some defects (e.g. dislocations, surface polishing damages, etc.). After the

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formation of graphene, the triangular pits became larger, and the bottom of the pits became flat. These results indicate that the etching by the solid-solution reaction of

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carbon with nickel was an anisotropic process.

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Fig. 5. (a) AFM image of the diamond surface before etching. (b) Cross-sectional image along the broken red line (A–B) in (a). 10

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Fig. 6 (a) AFM image of the diamond surface after etching by the solid-solution reaction of carbon with nickel. (b) Cross-sectional image along the broken red line (A–B) in (a).

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Figure 7(a) shows 2-D Raman mapping of IG of the graphene on diamond for the same region of the diamond surfaces shown in Fig. 6(a), and Fig. 7(b) shows the overlay of Figs. 6(a) and 7(a). As indicated by these figures, IG was high, particularly

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near the etched bunching steps, i.e., the edge of the pits. Namely, thick graphene layers

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were formed near the bunching steps. This result indicates that the number of graphene

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layers increased near the etched, bunching steps.

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Fig. 7 (a) 2-D Raman mapping of the IG of the graphene formed on diamond in the same region as that shown in Fig. 6(a). (b) Overlay image of Figs. 6(a) and 7(a).

Figure 8 shows the schematics of anisotropic etching by the solid-solution 12

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reaction of carbon with nickel and the formation of graphene layers via the out-diffusion of supersaturated carbon from nickel. The solid-solution reaction of carbon with nickel proceeds laterally from the steps on the diamond surface. The more steps there are on

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the diamond surface, the more the solid-solution reaction is promoted. Consequently,

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the number of graphene layers formed depends on the number of steps on the diamond

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surface.

Fig. 8 Schematics of anisotropic etching via the solid-solution reaction of carbon with nickel and the formation of graphene layers via the out-diffusion of supersaturated carbon from nickel. 13

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The graphene layers on the atomically flat diamond (111) surface showed p-type conduction with sheet carrier concentration and mobility values of 5.7×1013 cm−2

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and 140 cm2/Vs, respectively, by Hall effect measurements at room temperature. The

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mobility was one order of magnitude higher than that previously reported for graphene

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on diamond (111) [18]. We attributed this improvement in mobility to a reduction in

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carrier scattering resulting from the low roughness of the diamond surface. However, the obtained mobility value was lower than that of high-quality graphene on

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nanocrystalline diamond (ND) [33]. Compared with the graphene on ND, the graphene on the atomically flat diamond (111) surface had many rides, grain boundaries, and

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defects due to the D peaks (around 1350 cm−1). Thus, the low mobility was most likely due to the imperfections in the graphene. Additionally, an investigation of the band

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structure using density functional theory calculations [16] revealed that charge transfer occurs at the interface between graphene and diamond (111); this is accompanied by a

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shift in the Fermi level from the Dirac point, thereby resulting in a P-type doping. This doping probably caused the carrier concentration to increase to as high as 5.7 × 1013 cm−2. As a result, the mobility value decreased with increasing carrier concentration [36]. Thick graphene layers generated by the bunching steps of the diamond surface also lowered the mobility value. Therefore, we believe that eliminating the defects from diamond surfaces and forming wide terrace regions [37, 38] results in the formation of 14

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high-quality and uniform graphene on diamond.

Conclusions

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We fabricated graphene on atomically flat diamond (111) surfaces using nickel as a

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catalyst. 2-D Raman mapping indicated that the graphene was mainly deposited as

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multilayers. The mobility of the graphene layers was 140 cm2/Vs, which is one order of

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magnitude greater than the previously reported value. In addition, we found that the solid-solution reaction of carbon from diamond with nickel is anisotropic. These

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findings demonstrate that the number of graphene layers deposited depends on the

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number of steps on the diamond surface.

Prime novelty statement

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We successfully formed graphene layers on atomically flat diamond (111)

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surfaces via a solid-solution reaction of carbon with nickel.

Acknowledgement

This work was partially supported by the Kanazawa University SAKIGAKE Project.

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References [1] A.K. Geim, K.S. Novoselov, The rise of graphene, Nat. Mater. 6 (2007) 183–191 [2] K.I. Bolotin, K.J. Sikes, Z. Jiang, M. Klima, G. Fudenberg, J. Hone, P. Kim, H.L.

PT

Stormer, Ultrahigh electron mobility in suspended graphene, Solid State Commun.

RI

146 (2008) 351–355

SC

[3] M. Orlita, C. Faugeras, P. Plochocka, P. Neugebauer, G. Martinez, D.K. Maude,

NU

A.-L. Barra, M. Sprinkle, C. Berger, W.A. de Heer, M. Potemski, Approaching the Dirac Point in High-Mobility Multilayer Epitaxial Graphene, Phys. Rev. Lett. 101

MA

(2008) 267601.

[4] F. Schwierz, Graphene transistors, Nat. Nanotechnol. 5 (2010) 487–496.

PT E

D

[5] K S. Novoselov, A.K. Geim, S.V. Morozov, D. Jiang, Y. Zhang, S.V. Dubonos, I.V. Grigorieva, A.A. Firsov, Electric Field Effect in Atomically Thin Carbon Films,

CE

Science 306 (2004) 666–669.

[6] J. Yu, G. Liu, A. V. Sumant, V. Goyal, A.A. Balandin Graphene-on-Diamond

AC

Devices with Increased Current-Carrying Capacity: Carbon sp2-on-sp3 Technology, Nano Lett. 12 (2012) 1603–1608. [7] S. Ghosh, W. Bao, D.L. Nika, S. Subrina, E.P. Pokatilov, C.N. Lau, A.A. Balandin Dimensional crossover of thermal transport in few-layer graphene, Nat. Mater. 9 (2010) 555–558. [8] A.A. Balandin, S. Ghosh, W. Bao, I. Calizo, D. Teweldebrhan, F. Miao, C.N. Lau, 16

ACCEPTED MANUSCRIPT

Superior Thermal Conductivity of Single-Layer Graphene, Nano Lett. 8 (2008) 902–907. [9] K.S. Novoselov, A.K. Geim, S.V. Morozov, D. Jiang, M.I. Katsnelson, I.V.

PT

Grigorieva, S.V. Dubonos, A.A. Firsov Two-dimensional gas of massless Dirac

RI

fermions in graphene, Nature 438 (2005) 197–200.

SC

[10] T. Ando, Screening Effect and Impurity Scattering in Monolayer Graphene, J.

NU

Phys. Soc. Jpn. 75 (2006) 074716.

[11] K. Nomura, A.H. MacDonald Quantum Transport of Massless Dirac Fermions

MA

Phys. Rev. Lett. 98 (2007) 076602.

[12] E.H. Hwang, S. Adam, S.D. Sarma, Carrier Transport in Two-Dimensional

PT E

D

Graphene Layers, Phys. Rev. Lett. 98 (2007) 186806. [13] S. Fratini, F. Guinea, Substrate-limited electron dynamics in graphene, Phys. Rev.

CE

B 77 (2008) 195415.

[14] Y. Ma, Y. Dai, M. Guo, B. Huang, Graphene-diamond interface: Gap opening and

AC

electronic spin injection, Phys. Rev. B 85 (2012) 235448. [15] W. Hu, Z. Li, J. Yang, Structural, electronic, and optical properties of hybrid silicene and graphene nanocomposite, J. Chem. Phys. 138 (2013) 054701. [16] W. Hu, Z. Li, J. Yang, Diamond as an inert substrate of graphene J. Chem. Phys. 138 (2013) 054701. [17] Y. Wu, Y. Lin, A.A. Bol, K.A. Jenkins, F. Xia, D.B. Farmer, Y. Zhu, P. Avouris, 17

ACCEPTED MANUSCRIPT

High-frequency, scaled graphene transistors on diamond-like carbon, Nature 472 (2011) 74–78. [18] S. Ogawa, T. Yamada, S. Ishizduka, A. Yoshigoe, M. Hasegawa, Y. Teraoka, Y.

PT

Takakuwa, Vacuum Annealing Formation of Graphene on Diamond C(111)

RI

Surfaces Studied by Real-Time Photoelectron Spectroscopy, Jpn. J. Appl. Phys. 51

SC

(2012) 11PF02.

NU

[19] T. Shiga, S. Konabe, J. Shiomi, T. Yamamoto, S. Maruyama, S. Okada, Graphene-diamond hybrid structure as spin-polarized conducting wire with

MA

thermally efficient heat sinks, Appl. Phys. Lett. 100 (2012) 233101. [20] N. Tokuda, M. Fukui, T. Makino, D. Takeuchi, S. Yamasaki, T. Inokuma,

PT E

D

Formation of graphene-on-diamond structure by graphitization of atomically flat diamond (111) surface, Jpn. J. Appl. Phys. 52 (2013) (110121–1-4).

CE

[21] K. Ueda, S. Aichi, H. Asano, Direct formation of graphene layers on diamond by high-temperature annealing with a Cu catalyst, Diam. Relat. Mater. 63 (2016) 148–

AC

152.

[22] K. Ueda, S. Aichi, H. Asano, Photo-controllable memristive behavior of graphene/diamond heterojunctions, Appl. Phys. Lett. 108 (2016) 222102. [23] S. Amini, J. Garay, G. Liu, A.A. Balandin, R. Abbaschian, Growth of large-area graphene films from metal-carbon melts, J. Appl. Phys. 108 (2010) 094321. [24] S. Bae, H. Kim, Y. Lee, X. Xu, J. Park, Y. Zheng, J. Balakrishnan, T. Lei, 18

ACCEPTED MANUSCRIPT

H.R. Kim, Y. Il Song, Y. Kim, K.S. Kim, B. Özyilmaz, J. Ahn, B.H. Hong, S. Iijima, Roll-to-roll production of 30-inch graphene films for transparent electrodes, Nat. Nanotechnol. 5 (2010) 574–578.

PT

[25] L. Huanga, Q.H. Changa, G.L. Guoa, Y. Liua, Y.Q. Xiea, T. Wanga, B. Lingb, H.F.

RI

Yangb, Synthesis of high-quality graphene films on nickel foils by rapid thermal

SC

chemical vapor deposition, Carbon 50 (2012) 551–556.

NU

[26] J.M. García, R. He, M.P. Jiang, P. Kim, L.N. Pfeiffer, A. Pinczuk, Multilayer graphene grown by precipitation upon cooling of nickel on diamond, Carbon 49

MA

(2011) 1006–1012.

[27] B. Nguyen, J. Lin, D. Perng, Non-vacuum growth of graphene films using solid

PT E

D

carbon source, Appl. Phys. Lett.106 (2015) 221604. [28] J. Kwak, J.H. Chu, J. Choi, S. Park, H. Go, S.Y. Kim, K. Park, S. Kim, Y. Kim, E.

CE

Yoon, S. Kodambaka, S. Kwon, Near room-temperature synthesis of transfer-free graphene films, Nat. Commun. 3 (2012) 645.

AC

[29] D.Q. McNerny, B. Viswanath, D. Copic, F.R. Laye, C. Prohoda, A.C. Brieland-Shoultz, E.S. Polsen, N.T. Dee, V.S. Veerasamy, A.J. Hart, Direct fabrication of graphene on SiO2 enabled by thin film stress engineering, Scientific Reports 4 (2014) 5049. [30] H. Wang, G. Yu, Direct CVD Graphene Growth on Semiconductors and Dielectrics for Transfer-Free Device Fabrication, Advan. Mater. 25 (2016) 4956– 19

ACCEPTED MANUSCRIPT

4975. [31] W. Smirnov, J.J. Hees, D. Brink, W. Müller-Sebert, A. Kriele, O.A. Williams, C.E. Nebel, Anisotropic etching of diamond by molten Ni particles, Appl. Phys. Lett. 97

PT

(2010) 073117.

RI

[32] G. Prakash, M.A. Capano, M.L. Bolen, D. Zemlyanov, R.G. Reifenberger, AFM

SC

study of ridges in few-layer epitaxial graphene grown on the carbon-face of 4H–

NU

SiC, Carbon 48 (2010) 2383–2393.

[33] D. Berman, S.A. Deshmukh, B. Narayanan, S.K.R.S Sankaranarayanan, Z. Yan,

MA

A.A. Balandin, A. Zinovev, D. Rosenmann, A.V. Sumant, Metal-induced rapid

PT E

Commun. 7 (2016) 12099.

D

transformation of diamond into single and multilayer graphene on wafer scale, Nat.

[34] A.C. Ferrari, J.C. Meyer, V. Scardaci, C. Casiraghi, M. Lazzeri, F. Mauri, S.

CE

Piscanec, D. Jiang, K.S. Novoselov, S. Roth, A.K. Geim, Raman Spectrum of Graphene and Graphene Layers, Phys. Rev. Lett. 97 (2006) 187401.

AC

[35] R. Kato, K. Tsugawa, Y. Okigawa, M. Ishihara, T. Yamada, M. Hasegawa, Bilayer graphene synthesis by plasma treatment of copper foils without using a carbon-containing gas, Carbon 77 (2014) 823–828. [36] J.L. Tedesco, B.L. VanMil, R.L. Myers-Ward, J.M. McCrate, S.A. Kitt, P.M. Campbell, G.G. Jernigan, J.C. Culbertson, C.R. Eddy, Jr., D.K. Gaskill, Hall effect mobility of epitaxial graphene grown on silicon carbide, Appl. Phys. Lett. 95 (2009) 20

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12. [37] N. Tokuda, T. Makino, T. Inokuma, S. Yamasaki, Formation of step-free surfaces on diamond (111) mesas by homoepitaxial lateral growth, Jpn. J. Appl. Phys. 51

PT

(2012) 090107.

RI

[38] N. Tokuda, H. Umezawa, K. Yamabe, H. Okushi, S. Yamasaki, Growth of

SC

atomically step-free surface on diamond {111} mesas, Diamond Relat. Mater. 19

AC

CE

PT E

D

MA

NU

(2010) 288.

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Graphical abstract

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Highlights

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Graphene layers were fabricated on diamond (111) surfaces via annealing at 900°C for 1 min under Ar atmosphere with nickel as a catalyst. The diamond (111) surfaces under the graphene layers exhibited step-terrace structures with a root-mean-square roughness of 0.05 nm in the terrace region. The sheet hole concentration and mobility values of the graphene layers were estimated to be 5.7 × 1013 cm−2 and 140 cm2/Vs.

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