Graphene-Assisted Chemical Etching of Silicon Using Anodic

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Graphene-Assisted Chemical Etching of Silicon Using Anodic Aluminum Oxides as Patterning Templates Jungkil Francisco Kim, Dae Hun Lee, Ju Hwan Kim, and Suk-Ho Choi ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.5b07773 • Publication Date (Web): 16 Oct 2015 Downloaded from http://pubs.acs.org on October 18, 2015

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ACS Applied Materials & Interfaces

Graphene-Assisted Chemical Etching of Silicon Using Anodic Aluminum Oxides as Patterning Templates Jungkil Kim, Dae Hun Lee, Ju Hwan Kim, and Suk-Ho Choi* Department of Applied Physics and Institute of Natural Sciences, Kyung Hee University, Yongin 446-701, Korea KEYWORDS: Graphene, catalyst, chemical etching, silicon, nanostructures

ABSTRACT

We firstly report graphene-assisted chemical etching (GaCE) of silicon by using patterned graphene as an etching catalyst. Chemical-vapor-deposition-grown graphene transferred on a silicon substrate is patterned to a mesh with nano-hole arrays by oxygen plasma etching using an anodic- aluminum-oxide etching mask. The prepared graphene mesh/silicon is immersed in a mixture solution of hydrofluoric acid and hydro peroxide with various molecular fractions at optimized temperatures. The silicon underneath graphene mesh is then selectively etched to form aligned nano-pillar arrays. The morphology of the nanostructured silicon can be controlled to be smooth or porous depending on the etching conditions. The experimental results are systematically discussed based on possible mechanisms for GaCE of Si.

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1. Introduction In the last several years, graphene has attracted much attention due to its intriguing physicochemical properties.1-3 Many reports have proved successful applications of graphene as a building block for novel electronic/optical devices, transparent/flexible electrodes, and so on.4-6 Scientific and engineering fields for which graphene is potentially useful are actually unlimited. Here, taking advantages of excellent properties of graphene, such as chemical inertness, high electronegativity, and Earth-abundance, we report a new design to employ graphene instead of metal as an etching catalyst in metal-assisted chemical etching (MaCE). MaCE is one of the popular chemical methods to fabricate semiconductor nanostructures using noble metals (Au, Ag, Pt, Pd, Cu, and etc.) as the etching catalyst.7-10 Particularly, MaCE of Si has been intensively used for fabricating Si nanowires (SiNWs)/nano-holes and porous Si (PSi). Our recent studies have shown that structurally- and morphologically-controlled SiNWs and GaAs nanostructures are successfully prepared by MaCE.11-14 Furthermore, the MaCE-produced nanostructures have been well utilized as building blocks for photodetectors, light-emitting-diodes, and molecular sensors.15-17 Despite these promising results, conventional MaCE still has a drawback in that it should use only noble metals for the etching catalyst. Noble metals are expensive and it is difficult to remove them during the etching process. In conventional MaCE, strong acids such as nitric acid or aqua regia have to be employed to remove residual noble metals after the etching process.13,17 In contrast, graphene is composed of only carbon that is one of the Earth-abundant atoms, and it can be easily removed by the oxygen plasma treatment.18 In this regard, we propose graphene-assisted chemical etching (GaCE) of Si using graphene meshes with nano-hole arrays as the etching catalyst, which are replicated from anodic aluminum oxide (AAO) templates, for obtaining Si nano-pillar arrays and PSi.


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2. Experimental Section 2.1 Fabrication of Graphene Meshes A schematic diagram in Figure 1a illustrates the process of fabricating a graphene mesh with aligned hole arrays, as the etching catalyst in GaCE of Si, by using thin AAO as the patterning mask. The AAO membranes with aligned hole channels were widely used as patterning templates for various applications.13,19 For preparing the AAO membranes, 1st anodization was conducted on Al plates loaded in an electrochemical shell that is filled with sulfuric and oxalic acids under the external bias of 25 and 40 V for 24 h, respectively. Then, the aluminum oxide disk formed on the Al plate was selectively removed in chromic acid for 24 h at 50 oC for the embossed structure of Al to be exposed with six-fold alignments. The aluminum plates suffered from 2nd anodization for 1~2 min to form the thin AAO disk of 300~400 nm thickness. If the prepared AAO disk is thick enough to be rigid, it cannot be placed on the target substrate directly. Subsequently, the polymer layer was spin-coated on the AAO/Al plate, and the aluminum beneath AAO was selectively dissolved in the copper (II) chloride solution. The polymer layersupported AAO membrane was transferred on chemical-vapor-deposition-grown large-area graphene/Si substrate. The polymer layer was then removed by rinsing with acetone or chloroform for several min. Figure 1b shows the SEM image that describes the AAO transferred on graphene/Si substrate. The oxygen plasma process removed the graphene exposed to outside through the pores of the AAO, thereby leaving the graphene only underneath the AAO. The AAO membrane was then detached by scotch-taping exfoliation or dissolved in NaOH (or KOH), to finally produce the graphene mesh with hole arrays. 2.2 Fabrication of Graphene Dot Arrays


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First, a close-packed monolayer of polystyrene nanospheres (PS NSs) was assembled to have six-fold symmetry on the graphene/Si substrates, as shown in Figure 2a and b. For this, a mixture solution of 4% deionized (DI) water containing PS NSs of 100 nm diameter and ethanol (volume ratio = 1 : 1) was dropped onto top surface of a 5 x 5 cm2 SiO2 (thickness = 300 nm)/Si wafer that was leaned on a petri dish filled with DI water. The dropped mixture solution was then spread on the water surface, resulting in a monolayer of PS NSs floating on the water. The PS NSs monolayer was packed closely by dropping a solution of sodium dodecyl sulfate on the water surface, thereby altering the surface tension, and subsequently transferred on the graphene/Si substrate and dried. For the use of the PS NSs monolayer as a mask, O2-plasma treatment by reactive ion etching was done to reduce the diameter of PS NSs, which led to securing the room for making the colloidal particle arrays no longer close-packed. While PS NSs are etched by O2 plasma, graphene exposed to O2 plasma was also removed. As a result, graphene only underneath PS NSs were left, as shown Figure 2a and c. To remove PS NSs selectively, the prepared samples were washed out with acetone for several min, thereby forming aligned graphene nano-dot arrays, as shown in Figure 2a and d. The graphene nano-dot arrays can be formed by an alternative patterning method of graphene.20,21 2.3 Graphene Assisted Chemical Etching (GaCE) Following the similar procedure used in conventional MaCE, the prepared graphene nanostructures (mesh and dot arrays) on Si substrates were immersed in HF/H2O2 mixture solution with the various molar ratio of HF to H2O2 (referred to as e) for around 30 min at 25 50 oC under dark conditions.

3. Results and Discussion


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3.1. Hole Arrays in the Graphene Meshes In Figure 3a and b, SEM images show the graphene mesh with aligned hole arrays, which was patterned by using sulfuric and oxalic AAO membranes, respectively. The hole diameter of graphene mesh can be controlled by tuning the pore diameter of AAO that is determined by the fabrication conditions such as applied bias and the barrier layer opening time.22 The barrier layer of AAO was opened in the 5 wt% H3PO4 solution at 30 oC for various times, thereby controlling the diameter of pore on the backside of AAO. To get the quantitative information on the pore size distribution of the prepared AAO membranes, an image analysis was done on the SEM images (see supporting information Figure S1 and S2 for sulfuric and oxalic AAO, respectively.) by using an image processing software (e.g., ImageJ). The mean and standard deviation of the AAO pores, obtained from statistically-analyzed histograms (see supporting information Figure S3.), are summarized in Figure 3d and e for sulfuric and oxalic AAO, respectively. The diameter of the pores is linearly proportional to opening time. The shape and size of graphene mesh are determined by those of AAO as O2 plasma etching mask. While graphene was etched by the O2 plasma treatment, graphene underneath the edge of AAO channels was slightly etched, resulting in making the hole diameter of graphene mesh larger than that of AAO pore, as compared in Figure 3d and e. Quantitative analysis for estimating the mean and standard deviation of holes of graphene meshes was performed manually due to weak contrast differences of SEM images. In this method, the hole diameter of graphene mesh ranges from ~ 35 to ~ 85 nm while its density is ~ 1 x 1010/cm2. The SEM image in Figure 3b shows a graphene mesh of 65 nm diameter, distinguished from that of 41 nm diameter in Figure 3a. If AAO templates are prepared using phosphoric acid, the hole diameter would be controlled from ~ 200 to ~ 400 nm at a density of ~ 5 x 108/cm2.23 In previous studies, graphene nanostructures have been prepared by various polymer-based lithography techniques, which gives rise to residual molecules around graphene


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nanostructures due to the imperfect removal of polymers during patterning processes.24 Zeng, Z. Y. et al. reported the patterning technique of graphene mesh using AAO as well, but it was necessary to use polymer layer on graphene because the AAO as patterning templates was rigid and thick.25 In this work, a thin flexible AAO film was transferred on graphene directly without polymer, resulting in ultraclean graphene patterning. As shown in Figure 3c, an atomic force microscopic (AFM) image of graphene mesh confirms that no residuals remain on the graphene mesh/SiO2. An AFM height profile shows that the step between graphene mesh and SiO2 is around 0.7 nm, proving graphene is a monolayer. Raman spectra from the graphene sheet and mesh are displayed in Figure 3f. The peak frequencies of D and 2D bands are almost same for both graphene sheet and mesh. The D band shows larger peak intensity than the G band in the graphene mesh, indicating the defective nature of graphene mesh, possibly resulting from the dominant contribution from the edge states at the periphery of graphene mesh.26 The G band frequency of graphene mesh appears blueshifted with respect to that of graphene sheet. The FWHM of the G band and peak-intensity ratio (ID/IG) are larger in graphene mesh. 3.2. Si Nanostructures Fabricated by GaCE In conventional MaCE, noble metals are employed as catalyst to etch down the Si surface selectively in acidic mixture solutions.9,10 These traditional catalysts are essentially similar in two major properties, namely their electronegativity and chemical inertness. They are critical determining factors for being catalyst of MaCE. High electronegativity makes noble metals extract negative electrons from Si, and positive holes are injected into Si thereby oxidizing Si well. Strong chemical inertness makes noble metals retain their shape and material properties during chemical reactions. In particular, the electronegativity of carbon that comprises graphene is 2.55, larger than that of silicon (1.90) as well as those of conventionally-used noble metals in


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MaCE (2.54 and 1.94 for gold and silver, respectively). Additionally, it is also well known that graphene is extremely chemically stable.27,28 In this regard, graphene can be utilized as a useful catalyst instead of gold and silver. In GaCE, electrons in Si are extracted to the surface of graphene due to high electronegativity of graphene, and the extracted electrons are then consumed for the decomposition of H2O2. As a result, holes are produced in the valence band of Si, resulting in the oxidation of Si. In other words, the oxidation of Si is determined by the catalytic decomposition of H2O2 on the graphene surface (cathodic reaction). The oxidized Si is removed by HF in the etching solution (anodic reaction). The cyclic reaction brings about continuous etching of the graphene-attached Si. The amount of injected holes (the decomposition of H2O2) and the removal rate of oxidized Si are the key factors controlling etching phenomena in GaCE. The decomposition of H2O2 is very sensitive to the concentration of H2O2 and the reaction temperature.29 The removal rate of oxidized Si is governed by the amount of HF. When GaCE of p-Si with e = 4.586 was conducted at room temperature, only porous structures were generated on the Si surface (see the supporting information, Figure S4). GaCE of p-Si with high e (> 22.931), any significant etching phenomena did not occur, which can be attributed to the amount of holes not enough to oxidize the Si surface underneath the graphene mesh. At low e (< 11.466), the resulting structure of Si is porous over whole area. At high e, excessive decomposition of H2O2 occurs at the interface of graphene/etching solution due to the high concentration of H2O2, thereby injecting much holes into Si. However, the oxidized Si cannot be removed quickly due to the low concentration of HF, and so, the extra injected holes diffuse away from the etching front to other regions such as doping-induced defect sites, thereby making the whole area of Si porous. To secure enough decomposition of H2O2 for Si etching at high e, we performed GaCE at higher temperature. The decomposition of H2O2 is very sensitive to the


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reaction temperature. According to previous reports, the decomposition of H2O2 on the noble metals is enhanced as the temperature increases.29 The GaCE at 40 - 50 oC results in the production of solid Si nano-pillar arrays at e of around 45.8 and 7.6 for n- and p-Si, respectively. Figures 4a and b show the tilted-view SEM images of the p-Si nano-pillar arrays fabricated by GaCE with e of 7.6 at 50 oC. The diameter of Si nanopillars replicated by the graphene mesh is around 50 nm. By repeating the process, we could obtain some Si nano-pillars with pretty high aspect ratios of ∼3:1 and ∼6:1, as shown in Fig. 4, but they were formed on some part of the Si substrate, not on its whole area. Short Si nanopillars (aspect ratio ∼ 1:1) were also fabricated on considerable area of the Si substrate (see supporting information Figure S5). These results seem to be strongly related with the structural non-uniformity of graphene. Physical properties of graphene are very sensitive to defects and morphologies. It is widely known that the CVD graphene has defects such as grain boundaries and point defects.30 Moreover, the graphene mesh is more defective than the graphene sheet.31,32 As shown in Fig. 3(f), the Raman peak ratio (ID/IG) is over one, indicating the graphene mesh is very defective, resulting in lower carrier mobility compared to pristine graphene. This may give a negative effect on the catalytic behavior during GaCE because of the resulting retardation of carrier migration through the graphene mesh. We suggest that long Si nano-pillars could be fabricated only from the junction of Si/high-quality graphene (it can be single-crystalline graphene without defect sites). The quality of the CVD graphene is nowadays being enhanced, especially in view of grain size, thereby reducing the defect density, which will improve GaCE. The reason why GaCE of n-Si requires higher e than that of p-Si can be explained as follows. In the cathodic reaction (where the decomposition of H2O2 occurs), the cathodic current density (j) is generated between graphene and the etching solution. j is proportional to the electron density


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and the concentration of H2O2 ([H2O2]). Then, n-type Si that has electrons as majority carrier needs lower [H2O2] to generate j for the proper decomposition of H2O2 than p-type Si that has holes as majority carrier. For GaCE of n-Si with other e values below 22.9, the only harsh porous structure is observed on Si surface without graphene dots. GaCE of p-type Si is almost similar to that of n-type Si, however, the range of e is shifted to smaller value; the harsh porous surface is observed at e < 4.5. As discussed above, in GaCE at high temperature, e determines the resulting structure of Si. The kinetics of GaCE can be understood by the amount of injected holes into Si and the removal rate of oxidized Si, which is governed by e. The plan-view SEM image in Figure 5a shows p-Si nano-pillar arrays for e = 7.644 at 50 oC. As described in the schematic illustration, almost all holes injected into Si can be consumed by the oxidation of Si underneath graphene and the oxidized Si is removed due to the sufficient amount of HF, resulting in the formation of the Si nano-pillars with solid surface. In contrast, as e decreases, the porous structure is formed over whole area of Si. The GaCE of p-Si with e = 2.293 at 50 oC results in the PSi, as shown in the SEM image of Figure 5b, similar to the case of GaCE with high e at room temperature. Analogously, at much low e, the large extra amount of injected holes can diffuse away from Si covered by the graphene mesh to the bare surface of Si. In this case, the oxidation of bare Si surface would be kinetically favored even without catalysts in the crystal planes with lower density of silicon back bonds, resulting in anisotropic etching along direction. The GaCE of p-Si with e = 1.529 at 50 oC produces anisotropically-etched Si surface, as shown in the SEM image of Figure 5c. We also employed aligned graphene nano-dots as the etching catalyst of GaCE, which was prepared by PS NS lithography. GaCE of p-Si was performed using graphene nano-dots for e = 7.644 at 50 oC, thereby producing aligned Si hole arrays, as shown in Figure 2e. The diameter of


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Si nano-holes was also replicated by that of the graphene nano-dots. The graphene nano-dots as catalyst with their center regions wrinkled still remained inside Si holes. These results suggest that GaCE using other forms of graphene nanostructures as catalysts is also available for structural and morphological control of Si nanostructures.

4. Conclusion We proposed a new application of nanostructured graphene as catalyst for wet-chemical etching of Si. GaCE using graphene nanostructures such as mesh with hole arrays and aligned dot arrays well produced Si nano-pillars with smooth surface, Si hole arrays, and PSi by deliberately controlling the etching conditions. Based on these, GaCE allowed us not only to overcome drawbacks involved in conventional MaCE using expensive noble metals such as Au, Ag, Pt, Pd, and etc, but also to structurally and morphologically control Si nanostructures.


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FIGURES

Figure 1. (a) Schematic illustration describing the patterning process of a graphene mesh used for producing Si nanostructures. (b) SEM image of a thin AAO membrane on the graphene/Si substrate.

Figure 2. (a) Schematic illustration showing the preparation process of graphene dot arrays and Si hole arrays by GaCE. (b-e) SEM images corresponding to each fabrication step in (a).


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Figure 3. SEM images of graphene meshes that are patterned by using (a) sulfuric AAO and (b) oxalic AAO as the etching masks. (c) AFM image and its height profile of graphene mesh, indicating that the graphene mesh is a monolayer. (d), (e) Variations in the diameters of pore of AAO and hole of graphene mesh depending on the barrier layer opening time. (f) Raman spectra of graphene sheet and mesh.

Figure 4. SEM images showing Si nano-pillars with high aspect ratios of (a) ~ 3:1 and (b) ~ 6:1. The insert scale bars indicate 200 nm.


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Figure 5. Plan-view SEM images and schematic illustrations describing the etching mechanism for (a) Si nano-pillars, (b) porous Si, and (c) anisotropically etched Si.


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ASSOCIATED CONTENT Supporting Information Experimental details and Figures S1–S5. This material is available free of charge via the Internet at http://pubs.acs.org

AUTHOR INFORMATION Corresponding Author [email protected] Author Contributions Jungkil Kim proposed conceptual ideas, did most of the etching experiments, and wrote the paper. Dae Hun Lee fabricated graphene sheets. Ju Hwan Kim anodized aluminum disks. SukHo Choi initiated, supervised, and revised the manuscript. Funding Sources This work was supported by the National Research Foundation of Korea (NRF) grant funded by the ministry of Science, ICT & Future Planning (Grant No. 2011–0017373). Notes The authors declare no competing financial interests.


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REFERENCES (1) Novoselov, K. S.; Geim, A. K.; Morozov, S. V.; Jiang, D.; Zhang, Y.; Dubonos, S. V.; Grigorieva, I. V.; Firsov, A. A. Electric Field Effect in Atomically Thin Carbon Films Science 2004, 306, 666-669. (2) Zhang, Y. B.; Tan, Y. W.; Stormer, H. L.; Kim, P. Experimental Observation of The Quantum Hall Effect and Berry's Phase in Graphene Nature 2005, 438, 201-204. (3) Lee, C.; Wei, X. D.; Kysar, J. W.; Hone, J. Measurement of The Elastic Properties and Intrinsic Strength of Monolayer Graphene Science 2008, 321, 385-388. (4) Guo, C. X.; Guai, G. H.; Li, C. M. Graphene Based Materials: Enhancing Solar Energy Harvesting Adv. Energy Mater. 2011, 1, 448-452. (5) Sahoo, N. G.; Pan, Y. Z.; Li, L.; Chan, S. H. Graphene-Based Materials for Energy Conversion Adv. Mater. 2012, 24, 4203-4210. (6) Yin, Z. Y.; Zhu, J. X.; He, Q. Y.; Cao, X. H.; Tan, C. L.; Chen, H. Y.; Yan, Q. Y.; Zhang, H. Graphene-Based Materials for Solar Cell Applications Adv. Energy Mater. 2014, 4, 1. (7) Li, X.; Bohn, P. W. Metal-Assisted Chemical Etching in HF/H2O2 Produces Porous Silicon Appl. Phys. Lett. 2000, 77, 2572-2574. (8) Tsujino, K.; Matsumura, M. Boring Deep Cylindrical Nanoholes in Silicon Using Silver Nanoparticles as a Catalyst Adv. Mater. 2005, 17, 1045-1047. (9) Tsujino, K.; Matsumura, M. Helical Nanoholes Bored in Silicon by Wet Chemical Etching Using Platinum Nanoparticles as Catalyst Electrochem. Solid-State Lett. 2005, 8, C193-C095. (10) Peng, K. Q.; Hu, J. J.; Yan, Y. J.; Wu, Y.; Fang, H.; Xu, Y.; Lee, S. T.; Zhu, J. Fabrication of Single-Crystalline Silicon Nanowires by Scratching a Silicon Surface with Catalytic Metal Particles Adv. Funct. Mater. 2006, 16, 387-394. (11) Huang, Z. P.; Fang, H.; Zhu, J. Fabrication of Silicon Nanowire Arrays with Controlled Diameter, Length, and Density Adv. Mater. 2007, 19, 744-748. (12) DeJarld, M.; Shin, J. C.; Chern, W.; Chanda, D.; Balasundaram, K.; Rogers, J. A.; Li, X. L. Formation of High Aspect Ratio GaAs Nanostructures with Metal-Assisted Chemical Etching Nano Lett. 2011, 11, 5259-5263. (13) Kim, J.; Han, H.; Kim, Y. H.; Choi, S. H.; Kim, J. C.; Lee, W. Au/Ag Bilayered Metal Mesh as a Si Etching Catalyst for Controlled Fabrication of Si Nanowires ACS Nano 2011, 5, 32223229.


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Page 16 of 18

(14) Kim, J.; Kim, Y. H.; Choi, S. H.; Lee, W. Curved Silicon Nanowires with Ribbon-like Cross Sections by Metal-Assisted Chemical Etching ACS Nano 2011, 5, 5242-5248. (15) Mohseni, P. K.; Kim, S. H.; Zhao, X.; Balasundaram, K.; Kim, J. D.; Pan, L.; Rogers, J. A.; Coleman, J. J.; Li, X. L. GaAs Pillar Array-Based Light Emitting Diodes Fabricated by MetalAssisted Chemical Etching J. Appl. Phys. 2013, 114, 064909. (16) Kim, J.; Joo, S. S.; Lee, K. W.; Kim, J. H.; Shin, D. H.; Kim, S.; Choi, S. H. NearUltraviolet-Sensitive Graphene/Porous Silicon Photodetectors ACS Appl. Mater. Interfaces 2014, 6, 20880-20886. (17) Kim, J.; Oh, S. D.; Kim, J. H.; Shin, D. H.; Kim, S.; Choi, S. H. Graphene/Si-nanowire heterostructure molecular sensors Sci. Rep. 2014, 4, 5384. (18) Gokus, T.; Nair, R. R.; Bonetti, A.; Bohmler, M.; Lombardo, A.; Novoselov, K. S.; Geim, A. K.; Ferrari, A. C.; Hartschuh, A. Making Graphene Luminescent by Oxygen Plasma Treatment ACS Nano 2009, 3, 3963-3968. (19) Shimizu, T.; Xie, T.; Nishikawa, J.; Shingubara, S.; Senz, S.; Gosele, U. Synthesis of Vertical High-Density Epitaxial Si(100) Nanowire Arrays on a Si(100) Substrate Using an Anodic Aluminum Oxide Template Adv. Mater. 2007, 19, 917-920. (20) Moon, J.; An, J.; Sim, U.; Cho, S.-P.; Kang, J. H.; Chung, C.; Seo, J.-H.; Lee, J.; Nam, K. T.; Hong, B. H. One-Step Synthesis of N-doped Graphene Quantum Sheets from Monolayer Graphene by Nitrogen Plasma Adv. Mater. 2014, 26, 3501-3505. (21) Lee, J.; Kim, K.; Park, W. I.; Kim, B.-H.; Park, J. H.; Kim, T.-H.; Bong, S.; Kim, C.-H.; Chae, G. S.; Jun, M.; Hwang, Y.; Jung, Y. S.; Jeon, S. Uniform Graphene Quantum Dots Patterned from Self-Assembled Silica Nanodots Nano Lett. 2012, 12, 6078-6083. (22) Lillo, M.; Losic, D. Pore Opening Detection for Controlled Dissolution of Barrier Oxide Layer and Fabrication of Nanoporous Alumina with Through-Hole Morphology J. Membr. Sci. 2009, 327, 11-17. (23) Lee, W.; Ji, R.; Gosele, U.; Nielsch, K. Fast Fabrication of Long-Range Ordered Porous Alumina Membranes by Hard Anodization Nat. Mater. 2006, 5, 741-747. (24) Bai, J. W.; Zhong, X.; Jiang, S.; Huang, Y.; Duan, X. F. Graphene Nanomesh Nat. Nanotechnol. 2010, 5, 190-194.


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(25) Zeng, Z. Y.; Huang, X.; Yin, Z. Y.; Li, H.; Chen, Y.; Li, H.; Zhang, Q.; Ma, J.; Boey, F.; Zhang, H. Fabrication of Graphene Nanomesh by Using an Anodic Aluminum Oxide Membrane as a Template Adv. Mater. 2012, 24, 4138-4142. (26) Kim, S.; Shin, D. H.; Kim, C. O.; Kang, S. S.; Joo, S. S.; Choi, S. H.; Hwang, S. W.; Sone, C. Size-Dependence of Raman Scattering from Graphene Quantum Dots: Interplay Between Shape and Thickness Appl. Phys. Lett. 2013, 102, 053108. (27) Feng, J.; Qi, L.; Huang, J. Y.; Li, J. Geometric and Electronic Structure of Graphene Bilayer Edges Phys. Rev. B 2009, 80, 165407. (28) Liu, Z.; Suenaga, K.; Harris, P. J. F.; Iijima, S. Open and Closed Edges of Graphene Layers Phys. Rev. Lett. 2009, 102, 015501. (29) Goszner, K.; Bischof, H. The Decomposition of Hydrogen Peroxide on Silver-Gold Alloys J. Catal. 1974, 32, 175-182. (30) Li, X.; Cai, W; An, J.; Kim, S.; Nah, J.; Yang, D.; Piner, R.; Velamakanni, A.; Jung, I.; Tutuc, E.; Banerjee, S. K.; Colombo, L.; Ruoff, R. S. Large-Area Synthesis of High-Quality and Uniform Graphene Films on Copper Foils Science 2009, 324, 1312-1314. (31) Tsen, A. W.; Brown, L.; Levendorf, M. P.; Ghahari, F.; Huang, P. Y.; Havener, R. W.; Ruiz-Vargas, C. S.; Mullar, D. A.; Kim, P.; Park, J. Tailoring Electrical Transport Across Grain Boundaries in Polycrystalline Graphene Science. 2012, 336, 1143-1146. (32) Wei, Y.; Wu, J.; Yin, H.; Shi, X.; Yang, R.; Dresselhaus, D. The Nature of Strength Enhancement and Weakening by Pentagon-Hetagon Defects in Graphene Nat. Mater. 2012, 11, 759-763.


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Graphene-Assisted Chemical Etching of Silicon Using Anodic

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