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(a) (Color online) Schmatic showing the fabrication process flow of GFET on h-BN. Graphene is grown by Cu-catalytic thermal CVD process. (b) Raman spectra of the prepared sample with optical image (see the inset). Position “0” represents transferred graphene with no h-BN. At positions “1” and “2,” thin and thick h-BN flakes are underneath graphene, respectively.
(a) (Color online) Optical images of the fabricated GFETs with CVD-assembled graphene on SiO2 (top) and on h-BN (bottom), respectively. The devices 1-2, 1-3, and 1-4 have different gate lengths of 500 nm-wide graphene stripe with a shared source contact. The positions of exfoliated h-BN flake and CVD-assembled graphene are marked with dotted lines. (b) Measured R-VBG characteristics of the GFETs with CVD-assembled grapehe on SiO2 and h-BN substrate, respectively.
(a) (Color online) Small-signal transconductances of the GFETs with CVD-assembled graphene on two different substrates. ||max of the GFETs (gate length: 3 μm) on SiO2 and h-BN are 10 nS and 85 nS (device 1-2, solid line), respectively. For comparison, of the GFET with exfoliated graphene on SiO2 is also plotted (dash-dotted line). (b) Extracted effective mobility of the GFET with CVD-assembled graphene on SiO2 (top) and h-BN (bottom). The mobility is calculated using the output conductance obtained from ID – VDS curve. (c) AFM image of the GFET on h-BN shows that the h-BN thickness is ∼2.2 nm along the A-B line (partially folded flake). (d) h-BN is thinner underneath active graphene channel and its thickness is ignored in carrier density calculation.
Comparison of maximum transconductance and effective carrier mobility. All three GFETs have comparable gate length (2–2.2 μm).
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