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Electrophoretic deposition of ZnO on highly oriented pyrolytic graphite substrates
Accepted Manuscript Electrophoretic deposition of ZnO on highly oriented pyrolytic graphite substrates Faramarz Hossein-Babaei, Milad Ghalamboran, Ehsan Yousefiazari PII: DOI: Reference:
S0167-577X(17)31263-6 http://dx.doi.org/10.1016/j.matlet.2017.08.064 MLBLUE 23041
To appear in:
Materials Letters
Received Date: Revised Date: Accepted Date:
30 June 2017 10 August 2017 16 August 2017
Please cite this article as: F. Hossein-Babaei, M. Ghalamboran, E. Yousefiazari, Electrophoretic deposition of ZnO on highly oriented pyrolytic graphite substrates, Materials Letters (2017), doi: http://dx.doi.org/10.1016/j.matlet. 2017.08.064
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Electrophoretic deposition of ZnO on highly oriented pyrolytic graphite substrates Faramarz Hossein-Babaei1,*, Milad Ghalamboran 2, Ehsan Yousefiazari3
1
[email protected], [email protected], [email protected]
Abstract The electrophoretic deposition (EPD) of ZnO nanoparticles onto highly oriented pyrolytic graphite (HOPG) chips from a nonaqueous suspension is reported. Deposits are fast fired at 1200 ºC in vacuum, and lifted off the substrate using Kapton tape. The SEM micrographs revealed exfoliated graphene multilayer flakes on the back surface of the ZnO layers. The I-V characteristics of the ZnO/HOPG junctions demonstrate the atmospheric sensitivity of the junction energy barrier. This is the first report of using HOPG chips as substrates for the EPD of metal oxides. Forming metal oxide/graphene junctions has explicit technical difficulties, and the presented method is anticipated to find niche applications in fabricating wide area metal oxide/graphene multilayer junction devices such as radiation detectors and supercapacitors.
Keywords: Deposition; electrophoretic deposition; ZnO; carbon materials; HOPG; multilayer graphene;
Introduction Electrophoretic deposition (EPD) is a suitable method for depositing semiconductor nanoparticles onto conductive substrates [1]. Compared to other layer deposition techniques, EPD is of lower energy consumption, lower initial investment, higher deposition rate, and eco-friendliness [2, 3]. EPD is applicable to the mass production of both dense and porous coatings on different conductive substrates with various shapes, sizes, and surface properties [4-7]. Additionally, EPD has been utilized for depositing nanostructured materials composed of functional nanoparticles such as carbon nanotubes [8], graphene nanosheets [9], and metal oxide nanorods [10]. Graphene, a two-dimensional network of carbon hexagons, is viewed as the way to atomic-scale electronics [11]. The combination of excellent properties, such as visible transparency, high thermal and electrical
*
Corresponding author.
1
conductivity, mechanical strength, and chemical stability, vested in graphene is the reason behind the intense research on graphene electronics [12, 13]. Highly oriented pyrolytic graphite (HOPG) is a layered semimetal, consisting of many graphene sheets stacked on each other, and, hence, HOPG surface has the properties of a multilayer graphene [14, 15]. While working with graphene monolayers has explicit difficulties, clean HOPG surfaces can easily be obtained by cleaving bulk HOPG samples [14, 16]. Moreover, the high electrical conductivity and good chemical stability of the HOPG slabs make them suitable substrates for both anodic and cathodic EPD. The EPD of nanosized diamond particles onto the HOPG surface has been demonstrated two decades ago [17], but the present authors believe that combining the exclusive features of graphene with the versatile semiconducting properties of the nanostructured metal oxide layers via EPD would result in properties useful for fabricating many wide-area electronic and optoelectronic devices such as radiation detectors and supercapacitors [18, 19]. Here, we report using HOPG slabs as the substrates for the EPD of metal oxide semiconductors for the first time. The EPD of ZnO nanoparticles onto the freshly cleaved HOPG slabs is demonstrated as an example. Materials and Methods Suspensions of ZnO powder (Merck Millipore, 108846) in absolute acetone (Merck Millipore, 100014) are used for ZnO EPD. The EPD cell, as shown in Fig. 1a, comprises a borosilicate beaker which contains the suspension and houses the electrodes. The substrates are 5×10×0.2 mm3 chips of HOPG freshly cleaved from a HOPG slab. Photograph of the HOPG bulk and the cleaved chips are shown in Fig. 1b. SEM micrographs of the substrate cross-section and surface are respectively given as the insets (i) and (ii) in Fig. 1. A substrate is placed on the substrate holder and introduced into the cell. The deposition time is 10 min in all deposition runs, and the deposited mass is obtained by weighing the substrate before and after deposition. An advantage of using HOPG substrates in the experimental EPDs is that their thickness can be reduced by successive cleavages to low levels. With theoretical density of 2.26 g.cm-3, and the weight of an easy-to-use HOPG substrate with above given dimensions is 0.05 g. Low weight of the substrate allows more accurate deposit weighing.
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Fig. 1. (a) Schematic diagram of the setup used for the EPD of ZnO on HOPG chips. (b) Photograph demonstrating the cleavage of the bulk HOPG to produce HOPG chips. SEM micrographs of the HOPG surfaces are presented as insets in (b). The cell voltage and suspension concentration are varied in the 0-60 V and 0.5-50 mM ranges, respectively. The selection of parameter ranges are in accord with our previous experiences of ZnO EPD on metallic substrates [10]. Cell voltages are read directly between anode and cathode, while the temporal variations of the cell current are recorded by monitoring the voltage drop on a series resistor. Deposit weights at different EPD runs are presented in Fig. 2a, and a number of current vs. deposition time traces are shown in Fig. 2b. SEM micrographs of the deposits at two different experimental conditions are presented in Fig. 2a as insets (i) and (ii), demonstrating the independence of the apparent microstructure of the deposits from the EPD conditions. After deposition, the substrate is extracted from the cell, dried in air, and placed on a tungsten ribbon for fast firing at 1200 °C in vacuum (1 Pa) for 5 min to cause grain growth and partial stabilization of the porous zinc oxide layer on the substrate. Working in vacuum prevents oxidation of the HOPG substrate, which would occur spontaneously above 400 °C in air. The SEM micrograph of the zinc oxide layer after this process is shown in Fig. 2c depicting the formation of a three-dimensional network of ZnO particles over the substrate. Thermal annealings of the samples at 300 ºC (see below) either in air or vacuum, as demonstrated by the insets i and ii of Fig.2c, hardly affect their microstructures.
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Fig. 2. (a) Variations of the EPD rate with the applied electric field and ZnO concentration in the suspension. SEM micrographs of deposits at the indicated conditions are given as insets. (b) The temporal variations of cell current during EPD at the stated conditions. (c) SEM micrograph of the deposit after partial sintering at 1200 °C in vacuum. Insets i and ii are the micrographs of an as-deposited sample after thermal annealing at 300 ºC in air and vacuum, respectively. Discussion Experimental setup used for I-V characteristics recordings on ZnO/HOPG junctions is schematically presented in Fig. 3a. A triangular voltage waveform is applied between the substrate and the ZnO layer via a spring loaded titanium probe. The formation of ohmic contacts to oxide semiconductors is not straightforward [20, 21], but the contact between ZnO and Ti has been shown to be ohmic [14]. Hence, the nonlinearities observed in the I-V diagrams of the tested Ti/ZnO/HOPG structures are attributed to the ZnO/HOPG junctions. Prior to the I-V tests, the samples undergo a thermal annealing at 300 °C either in air or in vacuum. The room temperature I-V characteristics of the EPD-produced ZnO/HOPG diodes obtained for the vacuum- and airannealed samples are respectively given in Fig. 3b and c. The data presented in these diagrams are acquired from a single sample after consecutive thermal annealings. The transformation is repeatable; i.e. the type of I-V
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characteristics transforms from (b) to (c) and vice versa, according to the last annealing atmosphere. The results are consistent with the I-V characteristics recorded at similar conditions for the ZnO/HOPG junctions produced by the magnetron sputtering and spray pyrolysis of ZnO onto HOPG substrates [14, 22].
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Fig. 3. (a) The experimental setup used for the I-V measurements. (b-c) The I-V characteristics recorded for a ZnO/HOPG device after thermal annealing in vacuum (b) or in air (c); the logarithmic I-V plots are presented as insets in (b) and (c), respectively. The electrophoretically deposited oxide layer is lifted off the HOPG substrate using Kapton tape. The SEM observation revealed the attachment of large multilayer graphene flakes to the hind surface of ZnO. A micrograph of the exfoliated deposits is shown in Fig. 4; the graphene flakes are thin enough to allow observing the ZnO particles underneath. The EDS obtained from the location marked in Fig. 4a detected the presence of carbon as well as zinc and oxygen.
Fig. 4. (a) SEM micrograph of the back surface of the electrophoretically deposited ZnO layer taken after lift off from the HOPG substrate depicting an exfoliated multilayer graphene flake attached to the surface. (b) The schematic illustration of the method used for separating the partially sintered ZnO layers from the HOPG substrates. (c) EDS obtained from the marked location in (a).
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Conclusions The advantages of using HOPG chips as substrates for the EPD of semiconductor layers were specified, and the EPD of the metal oxide semiconductor ZnO onto HOPG substrates was demonstrated. It was shown that the main electronic features of the ZnO/HOPG junctions produced via EPD is the same as those produced by magnetron sputtering and spray pyrolysis. The EPD of nanostructured semiconductor layers onto HOPG substrates was established to provide a facile route for the experimental investigations on the devices with metal oxide/graphene structures. The method is anticipated to find niche applications in the fabrication of wide-area graphene-based electronic devices such as radiation detectors, chemical sensors, and supercapacitors.
References [1] M. Diba, D.W. Fam, A.R. Boccaccini, et al., Prog. Mater. Sci. 82 (2016) 83-117. [2] Y. Yang, J. Li, D. Chen, et al., ChemElectroChem 3(5) (2016) 757-763. [3] J. Ryu, K. No, Y. Kim, et al., Sci. Rep. 6 (2016) 36176. [4] L. Oakes, R. Carter, C.L. Pint, Nanoscale 8(46) (2016) 19368-19375. [5] Y. Yang, J. Li, D. Chen, et al., ACS Appl. Mater. Interfaces 8(40) (2016) 26730-26739. [6] F. Hosseinbabaei, B. Raissidehkordi, J. Eur. Ceram. Soc. 20(12) (2000) 2165-2168. [7] W.-c. Sun, P. Zhang, K. Zhao, et al., Wear 342 (2015) 172-180. [8] L. Oakes, A.P. Cohn, A.S. Westover, et al., Mater. Lett. 159 (2015) 261-264. [9] A. Chavez-Valdez, M. Shaffer, A. Boccaccini, J. Phys. Chem. B 117(6) (2012) 1502-1515. [10] F. Hossein-Babaei, F. Taghibakhsh, Electron. Lett. 36(21) (2000) 1815-1816. [11] E. Morales-Narváez, L.F. Sgobbi, S.A.S. Machado, et al., Prog. Mater. Sci. (2017). [12] C. Xie, C. Mak, X. Tao, et al., Adv. Funct. Mater. 27(19) (2017). [13] A. Di Bartolomeo, Phys. Rep. 606 (2016) 1-58. [14] F. Hossein-Babaei, N. Alaei-Sheini, M. Jahangiri, Mater. Lett. 192 (2017) 52-55. [15] A. Kinikar, T.P. Sai, S. Bhattacharyya, et al., Nat. Nanotechnol. 12 (2017) 564–568. [16] G. Zhang, M. Walker, P.R. Unwin, Langmuir 32(30) (2016) 7476-7484. [17] A. Affoune, B. Prasad, H. Sato, et al., Langmuir 17(2) (2001) 547-551. [18] H. Liu, Q. Sun, J. Xing, et al., ACS Appl. Mater. Interfaces 7(12) (2015) 6645-6651. [19] J. Cai, C. Lv, A. Watanabe, RSC Adv. 7(1) (2017) 415-422. [20] F. Hossein-Babaei, M.M. Lajvardi, N. Alaei-Sheini, Appl. Phys. Lett. 106(8) (2015) 083503.
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[21] F. Hossein-Babaei, S. Moghadam, S. Masoumi, Mater. Lett. 141 (2015) 141-144. [22] F. Hossein-Babaei, M. Akbari-Saatlu, Scr. Mater. 139 (2017) 77-82.
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Highlights:
HOPG chips are used as the substrates for the EPD of a metal oxide semiconductor. 3-D networks of zinc oxide crystallites are formed on multilayer graphene sheets. Exfoliation of graphene from HOPG with the peeled off ZnO deposits is demonstrated. A facile method for making multilayer graphene/metal oxide junctions is presented.
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Graphical abstract
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11
S0167-577X(17)31263-6 http://dx.doi.org/10.1016/j.matlet.2017.08.064 MLBLUE 23041
To appear in:
Materials Letters
Received Date: Revised Date: Accepted Date:
30 June 2017 10 August 2017 16 August 2017
Please cite this article as: F. Hossein-Babaei, M. Ghalamboran, E. Yousefiazari, Electrophoretic deposition of ZnO on highly oriented pyrolytic graphite substrates, Materials Letters (2017), doi: http://dx.doi.org/10.1016/j.matlet. 2017.08.064
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Electrophoretic deposition of ZnO on highly oriented pyrolytic graphite substrates Faramarz Hossein-Babaei1,*, Milad Ghalamboran 2, Ehsan Yousefiazari3
1
[email protected], [email protected], [email protected]
Abstract The electrophoretic deposition (EPD) of ZnO nanoparticles onto highly oriented pyrolytic graphite (HOPG) chips from a nonaqueous suspension is reported. Deposits are fast fired at 1200 ºC in vacuum, and lifted off the substrate using Kapton tape. The SEM micrographs revealed exfoliated graphene multilayer flakes on the back surface of the ZnO layers. The I-V characteristics of the ZnO/HOPG junctions demonstrate the atmospheric sensitivity of the junction energy barrier. This is the first report of using HOPG chips as substrates for the EPD of metal oxides. Forming metal oxide/graphene junctions has explicit technical difficulties, and the presented method is anticipated to find niche applications in fabricating wide area metal oxide/graphene multilayer junction devices such as radiation detectors and supercapacitors.
Keywords: Deposition; electrophoretic deposition; ZnO; carbon materials; HOPG; multilayer graphene;
Introduction Electrophoretic deposition (EPD) is a suitable method for depositing semiconductor nanoparticles onto conductive substrates [1]. Compared to other layer deposition techniques, EPD is of lower energy consumption, lower initial investment, higher deposition rate, and eco-friendliness [2, 3]. EPD is applicable to the mass production of both dense and porous coatings on different conductive substrates with various shapes, sizes, and surface properties [4-7]. Additionally, EPD has been utilized for depositing nanostructured materials composed of functional nanoparticles such as carbon nanotubes [8], graphene nanosheets [9], and metal oxide nanorods [10]. Graphene, a two-dimensional network of carbon hexagons, is viewed as the way to atomic-scale electronics [11]. The combination of excellent properties, such as visible transparency, high thermal and electrical
*
Corresponding author.
1
conductivity, mechanical strength, and chemical stability, vested in graphene is the reason behind the intense research on graphene electronics [12, 13]. Highly oriented pyrolytic graphite (HOPG) is a layered semimetal, consisting of many graphene sheets stacked on each other, and, hence, HOPG surface has the properties of a multilayer graphene [14, 15]. While working with graphene monolayers has explicit difficulties, clean HOPG surfaces can easily be obtained by cleaving bulk HOPG samples [14, 16]. Moreover, the high electrical conductivity and good chemical stability of the HOPG slabs make them suitable substrates for both anodic and cathodic EPD. The EPD of nanosized diamond particles onto the HOPG surface has been demonstrated two decades ago [17], but the present authors believe that combining the exclusive features of graphene with the versatile semiconducting properties of the nanostructured metal oxide layers via EPD would result in properties useful for fabricating many wide-area electronic and optoelectronic devices such as radiation detectors and supercapacitors [18, 19]. Here, we report using HOPG slabs as the substrates for the EPD of metal oxide semiconductors for the first time. The EPD of ZnO nanoparticles onto the freshly cleaved HOPG slabs is demonstrated as an example. Materials and Methods Suspensions of ZnO powder (Merck Millipore, 108846) in absolute acetone (Merck Millipore, 100014) are used for ZnO EPD. The EPD cell, as shown in Fig. 1a, comprises a borosilicate beaker which contains the suspension and houses the electrodes. The substrates are 5×10×0.2 mm3 chips of HOPG freshly cleaved from a HOPG slab. Photograph of the HOPG bulk and the cleaved chips are shown in Fig. 1b. SEM micrographs of the substrate cross-section and surface are respectively given as the insets (i) and (ii) in Fig. 1. A substrate is placed on the substrate holder and introduced into the cell. The deposition time is 10 min in all deposition runs, and the deposited mass is obtained by weighing the substrate before and after deposition. An advantage of using HOPG substrates in the experimental EPDs is that their thickness can be reduced by successive cleavages to low levels. With theoretical density of 2.26 g.cm-3, and the weight of an easy-to-use HOPG substrate with above given dimensions is 0.05 g. Low weight of the substrate allows more accurate deposit weighing.
2
Fig. 1. (a) Schematic diagram of the setup used for the EPD of ZnO on HOPG chips. (b) Photograph demonstrating the cleavage of the bulk HOPG to produce HOPG chips. SEM micrographs of the HOPG surfaces are presented as insets in (b). The cell voltage and suspension concentration are varied in the 0-60 V and 0.5-50 mM ranges, respectively. The selection of parameter ranges are in accord with our previous experiences of ZnO EPD on metallic substrates [10]. Cell voltages are read directly between anode and cathode, while the temporal variations of the cell current are recorded by monitoring the voltage drop on a series resistor. Deposit weights at different EPD runs are presented in Fig. 2a, and a number of current vs. deposition time traces are shown in Fig. 2b. SEM micrographs of the deposits at two different experimental conditions are presented in Fig. 2a as insets (i) and (ii), demonstrating the independence of the apparent microstructure of the deposits from the EPD conditions. After deposition, the substrate is extracted from the cell, dried in air, and placed on a tungsten ribbon for fast firing at 1200 °C in vacuum (1 Pa) for 5 min to cause grain growth and partial stabilization of the porous zinc oxide layer on the substrate. Working in vacuum prevents oxidation of the HOPG substrate, which would occur spontaneously above 400 °C in air. The SEM micrograph of the zinc oxide layer after this process is shown in Fig. 2c depicting the formation of a three-dimensional network of ZnO particles over the substrate. Thermal annealings of the samples at 300 ºC (see below) either in air or vacuum, as demonstrated by the insets i and ii of Fig.2c, hardly affect their microstructures.
3
Fig. 2. (a) Variations of the EPD rate with the applied electric field and ZnO concentration in the suspension. SEM micrographs of deposits at the indicated conditions are given as insets. (b) The temporal variations of cell current during EPD at the stated conditions. (c) SEM micrograph of the deposit after partial sintering at 1200 °C in vacuum. Insets i and ii are the micrographs of an as-deposited sample after thermal annealing at 300 ºC in air and vacuum, respectively. Discussion Experimental setup used for I-V characteristics recordings on ZnO/HOPG junctions is schematically presented in Fig. 3a. A triangular voltage waveform is applied between the substrate and the ZnO layer via a spring loaded titanium probe. The formation of ohmic contacts to oxide semiconductors is not straightforward [20, 21], but the contact between ZnO and Ti has been shown to be ohmic [14]. Hence, the nonlinearities observed in the I-V diagrams of the tested Ti/ZnO/HOPG structures are attributed to the ZnO/HOPG junctions. Prior to the I-V tests, the samples undergo a thermal annealing at 300 °C either in air or in vacuum. The room temperature I-V characteristics of the EPD-produced ZnO/HOPG diodes obtained for the vacuum- and airannealed samples are respectively given in Fig. 3b and c. The data presented in these diagrams are acquired from a single sample after consecutive thermal annealings. The transformation is repeatable; i.e. the type of I-V
4
characteristics transforms from (b) to (c) and vice versa, according to the last annealing atmosphere. The results are consistent with the I-V characteristics recorded at similar conditions for the ZnO/HOPG junctions produced by the magnetron sputtering and spray pyrolysis of ZnO onto HOPG substrates [14, 22].
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Fig. 3. (a) The experimental setup used for the I-V measurements. (b-c) The I-V characteristics recorded for a ZnO/HOPG device after thermal annealing in vacuum (b) or in air (c); the logarithmic I-V plots are presented as insets in (b) and (c), respectively. The electrophoretically deposited oxide layer is lifted off the HOPG substrate using Kapton tape. The SEM observation revealed the attachment of large multilayer graphene flakes to the hind surface of ZnO. A micrograph of the exfoliated deposits is shown in Fig. 4; the graphene flakes are thin enough to allow observing the ZnO particles underneath. The EDS obtained from the location marked in Fig. 4a detected the presence of carbon as well as zinc and oxygen.
Fig. 4. (a) SEM micrograph of the back surface of the electrophoretically deposited ZnO layer taken after lift off from the HOPG substrate depicting an exfoliated multilayer graphene flake attached to the surface. (b) The schematic illustration of the method used for separating the partially sintered ZnO layers from the HOPG substrates. (c) EDS obtained from the marked location in (a).
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Conclusions The advantages of using HOPG chips as substrates for the EPD of semiconductor layers were specified, and the EPD of the metal oxide semiconductor ZnO onto HOPG substrates was demonstrated. It was shown that the main electronic features of the ZnO/HOPG junctions produced via EPD is the same as those produced by magnetron sputtering and spray pyrolysis. The EPD of nanostructured semiconductor layers onto HOPG substrates was established to provide a facile route for the experimental investigations on the devices with metal oxide/graphene structures. The method is anticipated to find niche applications in the fabrication of wide-area graphene-based electronic devices such as radiation detectors, chemical sensors, and supercapacitors.
References [1] M. Diba, D.W. Fam, A.R. Boccaccini, et al., Prog. Mater. Sci. 82 (2016) 83-117. [2] Y. Yang, J. Li, D. Chen, et al., ChemElectroChem 3(5) (2016) 757-763. [3] J. Ryu, K. No, Y. Kim, et al., Sci. Rep. 6 (2016) 36176. [4] L. Oakes, R. Carter, C.L. Pint, Nanoscale 8(46) (2016) 19368-19375. [5] Y. Yang, J. Li, D. Chen, et al., ACS Appl. Mater. Interfaces 8(40) (2016) 26730-26739. [6] F. Hosseinbabaei, B. Raissidehkordi, J. Eur. Ceram. Soc. 20(12) (2000) 2165-2168. [7] W.-c. Sun, P. Zhang, K. Zhao, et al., Wear 342 (2015) 172-180. [8] L. Oakes, A.P. Cohn, A.S. Westover, et al., Mater. Lett. 159 (2015) 261-264. [9] A. Chavez-Valdez, M. Shaffer, A. Boccaccini, J. Phys. Chem. B 117(6) (2012) 1502-1515. [10] F. Hossein-Babaei, F. Taghibakhsh, Electron. Lett. 36(21) (2000) 1815-1816. [11] E. Morales-Narváez, L.F. Sgobbi, S.A.S. Machado, et al., Prog. Mater. Sci. (2017). [12] C. Xie, C. Mak, X. Tao, et al., Adv. Funct. Mater. 27(19) (2017). [13] A. Di Bartolomeo, Phys. Rep. 606 (2016) 1-58. [14] F. Hossein-Babaei, N. Alaei-Sheini, M. Jahangiri, Mater. Lett. 192 (2017) 52-55. [15] A. Kinikar, T.P. Sai, S. Bhattacharyya, et al., Nat. Nanotechnol. 12 (2017) 564–568. [16] G. Zhang, M. Walker, P.R. Unwin, Langmuir 32(30) (2016) 7476-7484. [17] A. Affoune, B. Prasad, H. Sato, et al., Langmuir 17(2) (2001) 547-551. [18] H. Liu, Q. Sun, J. Xing, et al., ACS Appl. Mater. Interfaces 7(12) (2015) 6645-6651. [19] J. Cai, C. Lv, A. Watanabe, RSC Adv. 7(1) (2017) 415-422. [20] F. Hossein-Babaei, M.M. Lajvardi, N. Alaei-Sheini, Appl. Phys. Lett. 106(8) (2015) 083503.
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[21] F. Hossein-Babaei, S. Moghadam, S. Masoumi, Mater. Lett. 141 (2015) 141-144. [22] F. Hossein-Babaei, M. Akbari-Saatlu, Scr. Mater. 139 (2017) 77-82.
8
Highlights:
HOPG chips are used as the substrates for the EPD of a metal oxide semiconductor. 3-D networks of zinc oxide crystallites are formed on multilayer graphene sheets. Exfoliation of graphene from HOPG with the peeled off ZnO deposits is demonstrated. A facile method for making multilayer graphene/metal oxide junctions is presented.
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Graphical abstract
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