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.


Influence of substrate velocity on graphene coverage, as shown by SEM images after CVD treatment of Cu. The large areas of similar contrast indicate Cu grains (with boundary indicated by the dashed lines in the 75 mm/min image), and the local dark regions within the individual grains correspond to graphene. Nanoscale domains of graphene are formed at short growth times (i.e., as observed for high substrate velocity, 500 mm/min) and coalesce to form larger domains for longer growth times (i.e., at lower substrate velocity). Prominent diagonal grooves in the 25, 250 and 500 mm/min images are due to the surface processing of the foil. High-magnification image of 500 mm/min sample most clearly shows isolated domains within a Cu grain.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f4: Influence of substrate velocity on graphene coverage, as shown by SEM images after CVD treatment of Cu. The large areas of similar contrast indicate Cu grains (with boundary indicated by the dashed lines in the 75 mm/min image), and the local dark regions within the individual grains correspond to graphene. Nanoscale domains of graphene are formed at short growth times (i.e., as observed for high substrate velocity, 500 mm/min) and coalesce to form larger domains for longer growth times (i.e., at lower substrate velocity). Prominent diagonal grooves in the 25, 250 and 500 mm/min images are due to the surface processing of the foil. High-magnification image of 500 mm/min sample most clearly shows isolated domains within a Cu grain.

Mentions: High-resolution SEM imaging on Cu was also used to examine the uniformity of graphene coverage at different velocities (Fig. 4). Judging by the surface contrast at low accelerating voltage, we find near complete graphene coverage at low substrate velocities (e.g., 2  mm/min), and isolated nanoscale graphene domains at high substrate velocities (e.g., 500 mm/min). This agrees with previous studies that found graphene growth begins by formation of nanoscale domains at nucleation sites on Cu, which can coalesce given sufficient time2930. The inverse relationship between graphene coverage and translation speed is also consistent with the Raman spectra (Fig. 3a). A high nucleation density could be conducive to high-speed growth if the graphene domains have a similar orientation and are able to coalesce into a single domain; however, as discussed later, the limited size and varied orientation of Cu grains presents a practical limit to production quality.


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)

Influence of substrate velocity on graphene coverage, as shown by SEM images after CVD treatment of Cu. The large areas of similar contrast indicate Cu grains (with boundary indicated by the dashed lines in the 75 mm/min image), and the local dark regions within the individual grains correspond to graphene. Nanoscale domains of graphene are formed at short growth times (i.e., as observed for high substrate velocity, 500 mm/min) and coalesce to form larger domains for longer growth times (i.e., at lower substrate velocity). Prominent diagonal grooves in the 25, 250 and 500 mm/min images are due to the surface processing of the foil. High-magnification image of 500 mm/min sample most clearly shows isolated domains within a Cu grain.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f4: Influence of substrate velocity on graphene coverage, as shown by SEM images after CVD treatment of Cu. The large areas of similar contrast indicate Cu grains (with boundary indicated by the dashed lines in the 75 mm/min image), and the local dark regions within the individual grains correspond to graphene. Nanoscale domains of graphene are formed at short growth times (i.e., as observed for high substrate velocity, 500 mm/min) and coalesce to form larger domains for longer growth times (i.e., at lower substrate velocity). Prominent diagonal grooves in the 25, 250 and 500 mm/min images are due to the surface processing of the foil. High-magnification image of 500 mm/min sample most clearly shows isolated domains within a Cu grain.
Mentions: High-resolution SEM imaging on Cu was also used to examine the uniformity of graphene coverage at different velocities (Fig. 4). Judging by the surface contrast at low accelerating voltage, we find near complete graphene coverage at low substrate velocities (e.g., 2  mm/min), and isolated nanoscale graphene domains at high substrate velocities (e.g., 500 mm/min). This agrees with previous studies that found graphene growth begins by formation of nanoscale domains at nucleation sites on Cu, which can coalesce given sufficient time2930. The inverse relationship between graphene coverage and translation speed is also consistent with the Raman spectra (Fig. 3a). A high nucleation density could be conducive to high-speed growth if the graphene domains have a similar orientation and are able to coalesce into a single domain; however, as discussed later, the limited size and varied orientation of Cu grains presents a practical limit to production quality.

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.