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Carrier density modulation in graphene underneath Ni electrode
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10.1063/1.4813216
/content/aip/journal/jap/114/2/10.1063/1.4813216
http://aip.metastore.ingenta.com/content/aip/journal/jap/114/2/10.1063/1.4813216
View: Figures

Figures

Image of FIG. 1.
FIG. 1.

(bottom) Schematic of the device with the floating metal on the graphene channel, showing two current flow paths. (top) Schematic of the contact region, showing the transfer length ().

Image of FIG. 2.
FIG. 2.

(a) Optical micrograph of the fabricated monolayer graphene FET device showing the four metal electrodes on the graphene channel. The contact metal was Ni, and ohmic contacts were confirmed for all electrodes. (b) Schematic top and side views of the device for extracting the resistivity of the graphene/metal double-layered structure.

Image of FIG. 3.
FIG. 3.

(a) Intrinsic graphene resistivity () and for various as a function of . (b) Sheet resistivities of intrinsic graphene channel () and graphene/metal double-layers with various as a function of .

Image of FIG. 4.
FIG. 4.

Resistor network model for the device in Fig. 2 .

Image of FIG. 5.
FIG. 5.

(a) Current flow ratio in graphene (/) calculated at  = 1 m and  = DP for various . The larger prevents the current from flowing into the metal. (b) Current flow ratio in graphene (/) calculated at  = 1× 10 Ω m and  = DP for various . The current flow ratio in graphene increases with decreasing .

Image of FIG. 6.
FIG. 6.

Calculated sheet resistivities for the graphene/metal double-layered structure using the experimental value of , where the DP shift is not considered.

Image of FIG. 7.
FIG. 7.

(a) Optical micrograph and (b) schematic of the bilayer-graphene FET device for direct measurements. The shape of graphene was etched by O plasma before the metal deposition; three sets of voltage probes A–C are shown.

Image of FIG. 8.
FIG. 8.

(a) Sheet resistivities of intrinsic bilayer graphene channel () and graphene/metal double-layered structure with various positions. A–C indicate measured positions in Fig. 7(b) . (b) Calculated sheet resistivities for the graphene/metal double-layered structure using the experimental value of , where the DP shift is not considered. D is the calculation result from the voltage difference between 0 m and 1 m from the metal edge.

Image of FIG. 9.
FIG. 9.

Relationship between work function for various metals and doping polarity in graphene reported in the literature. The ideal doping polarity is hatched based on the work function difference between graphene (4.5 eV) and metals. White circles indicate the doping polarity judged from the asymmetry of the current-gate voltage curve, while gray circles indicate the doping polarity judged from the DP shift when metal particles are deposited on the graphene channel. The numbers in the circles show the references ( ) and “P” indicates the present results.

Image of FIG. 10.
FIG. 10.

(a) Optical micrograph of graphene on the SiO substrate. The EBSP orientation map of the normal direction (ND) is colored using the inverse pole figure triangle. Both the ND and the transverse direction (TD) show a single color, which suggests that Ni(111) grew epitaxially on the graphene. (b) Optical micrograph of the graphene FET device with a Ni electrode on the channel. The EBSP orientation map of the ND is colored using the inverse pole figure triangle.

Image of FIG. 11.
FIG. 11.

(a) Optical micrograph of the device fabricated with a resist-free process using a Si wafer mask. Thick Ni ∼15 nm, thin Ni ∼4 nm. (b) Schematic of the -dependent Raman measurement system, where the thick Ni was directly contacted by the W prober tip. An objective lens (×50) with a long working distance was used.

Image of FIG. 12.
FIG. 12.

G-band position as a function of for different devices: (i) and (ii) for the device fabricated with a resist-free process in Fig. 11(a) and (iii) for the device fabricated with a resist process in Fig. 10(b) .

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/content/aip/journal/jap/114/2/10.1063/1.4813216
2013-07-11
2014-04-18
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Carrier density modulation in graphene underneath Ni electrode
http://aip.metastore.ingenta.com/content/aip/journal/jap/114/2/10.1063/1.4813216
10.1063/1.4813216
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