Limits...
High-speed roll-to-roll manufacturing of graphene using a concentric tube CVD reactor.

Polsen ES, McNerny DQ, Viswanath B, Pattinson SW, John Hart A - Sci Rep (2015)

Bottom Line: We show that a smooth isothermal transition between the reducing and carbon-containing atmospheres, enabled by injection of the carbon feedstock via radial holes in the inner tube, is essential to high-quality roll-to-roll graphene CVD.We discuss how the foil quality and microstructure limit the uniformity of graphene over macroscopic dimensions.We conclude by discussing means of scaling and reconfiguring the CTCVD design based on general requirements for 2-D materials manufacturing.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, University of Michigan, 2350 Hayward St., Ann Arbor, MI 48109, USA.

ABSTRACT
We present the design of a concentric tube (CT) reactor for roll-to-roll chemical vapor deposition (CVD) on flexible substrates, and its application to continuous production of graphene on copper foil. In the CTCVD reactor, the thin foil substrate is helically wrapped around the inner tube, and translates through the gap between the concentric tubes. We use a bench-scale prototype machine to synthesize graphene on copper substrates at translation speeds varying from 25 mm/min to 500 mm/min, and investigate the influence of process parameters on the uniformity and coverage of graphene on a continuously moving foil. At lower speeds, high-quality monolayer graphene is formed; at higher speeds, rapid nucleation of small graphene domains is observed, yet coalescence is prevented by the limited residence time in the CTCVD system. We show that a smooth isothermal transition between the reducing and carbon-containing atmospheres, enabled by injection of the carbon feedstock via radial holes in the inner tube, is essential to high-quality roll-to-roll graphene CVD. We discuss how the foil quality and microstructure limit the uniformity of graphene over macroscopic dimensions. We conclude by discussing means of scaling and reconfiguring the CTCVD design based on general requirements for 2-D materials manufacturing.

No MeSH data available.


Analysis of sequential stages of R2R graphene growth: reduction of Cu, graphene nucleation, and graphene growth, as determined by the position of the foil along the CTCVD reactor. Translation of the Cu substrate was stopped to “freeze” the various stages along the length of the substrate while the system was cooled rapidly. a) Schematic of the CTCVD with axial positions highlighted relative to the beginning of the heated zone (the foil is translating left-to-right). b) Visible light microscopy (top) and SEM (bottom) images of a Cu substrate at various positions along the length of the CTCVD reactor (translated at 25 mm/min). Cu grain boundaries become visible as the oxide layer is reduced (x = 100 mm, left), followed by nucleation of graphene near the injection holes (x = 125 mm, middle), transitioning to near full graphene coverage prior to exiting the heated zone (x = 225 mm, right).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4440526&req=5

f6: Analysis of sequential stages of R2R graphene growth: reduction of Cu, graphene nucleation, and graphene growth, as determined by the position of the foil along the CTCVD reactor. Translation of the Cu substrate was stopped to “freeze” the various stages along the length of the substrate while the system was cooled rapidly. a) Schematic of the CTCVD with axial positions highlighted relative to the beginning of the heated zone (the foil is translating left-to-right). b) Visible light microscopy (top) and SEM (bottom) images of a Cu substrate at various positions along the length of the CTCVD reactor (translated at 25 mm/min). Cu grain boundaries become visible as the oxide layer is reduced (x = 100 mm, left), followed by nucleation of graphene near the injection holes (x = 125 mm, middle), transitioning to near full graphene coverage prior to exiting the heated zone (x = 225 mm, right).

Mentions: To further ascertain the substrate treatment kinetics within the CTCVD reactor, a Cu foil sample undergoing constant velocity processing was abruptly stopped and cooled rapidly by opening the furnace cover and applying a cold air stream across the reactor wall with a fan. Optical images and SEM images at marked locations on the substrate show the graphene coverage as a function of time in the reactor (Fig. 6a-b). Raman spectra of these locations are shown in the Supporting Information, Fig. S7. Emergence of visible grain boundaries upon annealing indicates that the surface oxide layer is reduced during H2 annealing at elevated temperature. At 25 mm/min, the exposure of the grain boundaries during the annealing of the Cu requires ~100 mm of travel (4 min residence time), and at ~125 mm (~25 mm upstream of the inner tube injection holes) we find that Cu grains begin to darken optically, and nanoscale graphene domains are found in the SEM images. This is also the first location along the length of the substrate that G, D and 2D peaks are observable on the Raman spectrum. As the foil progresses further through the reactor, maximum coverage of graphene is achieved between the 175 mm and 225 mm locations (as determined by Raman spectra line scans along the width of the foil where D, G and 2D peaks were always apparent, peak intensity ratios I2D/IG and IG/ID were maximized, and the coverage depicted in the SEM images), representing 120–240 seconds of exposure beyond the nucleation point. Moreover, we find some Cu grains become nearly fully covered within less than 45 seconds (at the end of a 250 mm/min run), compared to the much longer time to achieve maximum coverage (120–240 seconds) on the polycrystalline foil (See Supporting Information, Fig. S8). Improved crystallinity and surface conditions of the foil could therefore greatly increase the throughput and quality of the R2R CVD process.


High-speed roll-to-roll manufacturing of graphene using a concentric tube CVD reactor.

Polsen ES, McNerny DQ, Viswanath B, Pattinson SW, John Hart A - Sci Rep (2015)

Analysis of sequential stages of R2R graphene growth: reduction of Cu, graphene nucleation, and graphene growth, as determined by the position of the foil along the CTCVD reactor. Translation of the Cu substrate was stopped to “freeze” the various stages along the length of the substrate while the system was cooled rapidly. a) Schematic of the CTCVD with axial positions highlighted relative to the beginning of the heated zone (the foil is translating left-to-right). b) Visible light microscopy (top) and SEM (bottom) images of a Cu substrate at various positions along the length of the CTCVD reactor (translated at 25 mm/min). Cu grain boundaries become visible as the oxide layer is reduced (x = 100 mm, left), followed by nucleation of graphene near the injection holes (x = 125 mm, middle), transitioning to near full graphene coverage prior to exiting the heated zone (x = 225 mm, right).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4440526&req=5

f6: Analysis of sequential stages of R2R graphene growth: reduction of Cu, graphene nucleation, and graphene growth, as determined by the position of the foil along the CTCVD reactor. Translation of the Cu substrate was stopped to “freeze” the various stages along the length of the substrate while the system was cooled rapidly. a) Schematic of the CTCVD with axial positions highlighted relative to the beginning of the heated zone (the foil is translating left-to-right). b) Visible light microscopy (top) and SEM (bottom) images of a Cu substrate at various positions along the length of the CTCVD reactor (translated at 25 mm/min). Cu grain boundaries become visible as the oxide layer is reduced (x = 100 mm, left), followed by nucleation of graphene near the injection holes (x = 125 mm, middle), transitioning to near full graphene coverage prior to exiting the heated zone (x = 225 mm, right).
Mentions: To further ascertain the substrate treatment kinetics within the CTCVD reactor, a Cu foil sample undergoing constant velocity processing was abruptly stopped and cooled rapidly by opening the furnace cover and applying a cold air stream across the reactor wall with a fan. Optical images and SEM images at marked locations on the substrate show the graphene coverage as a function of time in the reactor (Fig. 6a-b). Raman spectra of these locations are shown in the Supporting Information, Fig. S7. Emergence of visible grain boundaries upon annealing indicates that the surface oxide layer is reduced during H2 annealing at elevated temperature. At 25 mm/min, the exposure of the grain boundaries during the annealing of the Cu requires ~100 mm of travel (4 min residence time), and at ~125 mm (~25 mm upstream of the inner tube injection holes) we find that Cu grains begin to darken optically, and nanoscale graphene domains are found in the SEM images. This is also the first location along the length of the substrate that G, D and 2D peaks are observable on the Raman spectrum. As the foil progresses further through the reactor, maximum coverage of graphene is achieved between the 175 mm and 225 mm locations (as determined by Raman spectra line scans along the width of the foil where D, G and 2D peaks were always apparent, peak intensity ratios I2D/IG and IG/ID were maximized, and the coverage depicted in the SEM images), representing 120–240 seconds of exposure beyond the nucleation point. Moreover, we find some Cu grains become nearly fully covered within less than 45 seconds (at the end of a 250 mm/min run), compared to the much longer time to achieve maximum coverage (120–240 seconds) on the polycrystalline foil (See Supporting Information, Fig. S8). Improved crystallinity and surface conditions of the foil could therefore greatly increase the throughput and quality of the R2R CVD process.

Bottom Line: We show that a smooth isothermal transition between the reducing and carbon-containing atmospheres, enabled by injection of the carbon feedstock via radial holes in the inner tube, is essential to high-quality roll-to-roll graphene CVD.We discuss how the foil quality and microstructure limit the uniformity of graphene over macroscopic dimensions.We conclude by discussing means of scaling and reconfiguring the CTCVD design based on general requirements for 2-D materials manufacturing.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, University of Michigan, 2350 Hayward St., Ann Arbor, MI 48109, USA.

ABSTRACT
We present the design of a concentric tube (CT) reactor for roll-to-roll chemical vapor deposition (CVD) on flexible substrates, and its application to continuous production of graphene on copper foil. In the CTCVD reactor, the thin foil substrate is helically wrapped around the inner tube, and translates through the gap between the concentric tubes. We use a bench-scale prototype machine to synthesize graphene on copper substrates at translation speeds varying from 25 mm/min to 500 mm/min, and investigate the influence of process parameters on the uniformity and coverage of graphene on a continuously moving foil. At lower speeds, high-quality monolayer graphene is formed; at higher speeds, rapid nucleation of small graphene domains is observed, yet coalescence is prevented by the limited residence time in the CTCVD system. We show that a smooth isothermal transition between the reducing and carbon-containing atmospheres, enabled by injection of the carbon feedstock via radial holes in the inner tube, is essential to high-quality roll-to-roll graphene CVD. We discuss how the foil quality and microstructure limit the uniformity of graphene over macroscopic dimensions. We conclude by discussing means of scaling and reconfiguring the CTCVD design based on general requirements for 2-D materials manufacturing.

No MeSH data available.