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Results: 5

1.
Figure 1

Figure 1. From: High Yield Chemical Vapor Deposition Growth of High Quality Large-Area AB Stacked Bilayer Graphene.

(a) A schematic illustration of the bilayer graphene growth. Carbon fragments come from the uncovered upstream Cu catalyst are continuously transported downstream for the growth of bilayer graphene. (b, c) SEM images of monolayer (1L) and bilayer (2L) graphene at upstream end and center of the Cu substrate, respectively. The bright strips in b are the exposed copper surface between graphene domains, and the darker hexagonal contrast corresponds to the bilayer graphene. Scale bars are 20 μm.

Lixin Liu, et al. ACS Nano. 2012 September 25;6(9):8241-8249.
2.
Figure 4

Figure 4. From: High Yield Chemical Vapor Deposition Growth of High Quality Large-Area AB Stacked Bilayer Graphene.

(a) HRTEM image of graphene synthesized by the two-step process, suspended on a holey carbon TEM grid. The monolayer and bilayer regions are marked by the blue and red circles. (b, c) SAED patterns of monolayer and AB stacked bilayer graphene regions in (a), respectively. (d) SAED pattern obtained from disoriented bilayer graphene, showing two sets of diffraction spots with a 28.9° rotation. (e, f) Profile plots of diffraction peak intensities along arrows in (b and (c), respectively.

Lixin Liu, et al. ACS Nano. 2012 September 25;6(9):8241-8249.
3.
Figure 5

Figure 5. From: High Yield Chemical Vapor Deposition Growth of High Quality Large-Area AB Stacked Bilayer Graphene.

(a) Schematic illustration of bilayer graphene device with single back-gate or dual-gate. (b) Device resistance v.s. back gate voltage (VBG). The hollow circles represent experimental data point and red line is the modeling fit to extract carrier mobility. (c) Histogram of the carrier (hole) mobility distribution for back-gated bilayer graphene devices. The devices studied in b and c have a channel length of 7.5 μm and width of 7.5 μm. (d) 2D plot of Rtotal as functions of both top gate voltage (VTG) and VBG of a dual-gate bilayer graphene device. (e) A series of R v.s. VTG curves at different value of fixed VBG ranging from −80 to 80 V, with 20 V increment. (f) Resistance at Dirac point under different displacement field.

Lixin Liu, et al. ACS Nano. 2012 September 25;6(9):8241-8249.
4.
Figure 2

Figure 2. From: High Yield Chemical Vapor Deposition Growth of High Quality Large-Area AB Stacked Bilayer Graphene.

(a) SEM image of the initial monolayer (1L) and bilayer (2L) graphene domains transferred onto SiO2/Si substrate synthesized in a 2-min growth with H2/CH4 ratio of 40 under 5 mbar at 1050 °C. The hexagonal bilayer domains are typically located at the centers of the monolayer domains. (b) Raman spectra of the monolayer and bilayer graphene. Bilayer graphene is presented by two different stacking arrangements: AB stacking and disoriented stacking. (c) and (d) Enlarged SEM images of the AB stacked and disoriented bilayer graphene domains, respectively. The insets are the schematic diagrams for the two different stacking orders. (e) AFM image of a graphene domain on SiO2 substrate. The two white lines near center and edge of the domain indicate the sections corresponding to the depth profiles shown in (f) and (g). The height difference between the two dashed lines is ~ 0.34 nm in (f) and ~ 1.0 nm in (g), respectively.

Lixin Liu, et al. ACS Nano. 2012 September 25;6(9):8241-8249.
5.
Figure 3

Figure 3. From: High Yield Chemical Vapor Deposition Growth of High Quality Large-Area AB Stacked Bilayer Graphene.

SEM images of monolayer and bilayer graphene on the center of Cu foil synthesized with H2/CH4 ratio of 40 under 1 mbar at 1050 °C for (a) 2 min and (b) 1 hour growth. (c) SEM image shows that the bilayer graphene coverage is increased dramatically by increasing pressure to 5 mbar for 1 hour growth after the first 2 min low pressure nucleation step. (d) SEM image of higher coverage of bilayer graphene obtained after extending the growth duration to 3 hours. Scale bars are 20 μm. (e) Coverage statistics of different layers for the sample shown in (d) demonstrates that ~ 99 % of surface area is covered by bilayer graphene. (f) Representative Raman spectra of the two different stacked bilayer graphene in (d). (g, h) Histograms of the Raman spectrum 2D band FWHMs and I2D/IG ratio of the bilayer graphene. (i) Stacking ratio statistics of the bilayer graphene based on (g, h).

Lixin Liu, et al. ACS Nano. 2012 September 25;6(9):8241-8249.

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