Journal: Nature Communications

Article Title: Integrated wafer-scale ultra-flat graphene by gradient surface energy modulation

doi: 10.1038/s41467-022-33135-w

Figure Lengend Snippet: a Schematic illustration of wafer-scale ultra-flat graphene transfer via gradient surface energy modulation. b The structure of transfer medium, in which different layers with gradient surface energy are designed ( γ 1 > γ 2 , γ 3 ≥ γ 4 ). Left and right figures show the adhesion and release procedures in panel ( a ). Note that the surface energy of SiO 2 /Si ( γ 1 ) is larger than that of graphene/borneol ( γ 2 ), enabling reliable adhesion as the middle picture shows. Also, the surface energy of PDMS ( γ 4 ) is the lowest, leading to the intact release of graphene onto the target substrate. c The surface energies of different surfaces calculated from measured contact angles. Insets: images showing contact angles of water on different surfaces. Error bars indicate standard deviations of surface energies and contact angles for different surface. d Optical image of 4-inch transferred graphene on SiO 2 /Si wafer. e Histograms of coverage of transferred graphene. Inset: optical microscopy image of transferred graphene. f Scanning electron microscopy images of GSE-transferred graphene and PMMA-transferred graphene. g Histograms of particle number per 10 × 10 μm 2 from 80 AFM images of GSE-transferred and 50 AFM images of PMMA-transferred graphene. Insets: Typical AFM images of GSE-transferred and PMMA-transferred graphene. h Histograms of wrinkle number per 5 × 5 μm 2 issued from AFM images of transferred ultra-flat and rough graphene. Insets: AFM images of transferred ultra-flat and rough graphene.

Article Snippet: As shown in Fig. , the integrated graphene emitter device arrays with 4-inch GSE-transferred graphene wafer were successfully obtained.

Techniques: Microscopy, Electron Microscopy

Journal: Nature Communications

Article Title: Integrated wafer-scale ultra-flat graphene by gradient surface energy modulation

doi: 10.1038/s41467-022-33135-w

Figure Lengend Snippet: a , b Spatial sheet resistance maps of GSE-transferred graphene ( a ) and PMMA-transferred graphene ( b ) on 4-inch SiO 2 /Si wafer. Note that the sheet resistance deviation of GSE-transferred graphene is ~6%. c , d Spatial G-peak’s position maps of GSE-transferred ( c ) and PMMA-transferred ( d ) graphene. The peak position of G-band of PMMA-transferred graphene is blue shifted. e Correlation map of the Raman G and 2D peak positions of GSE- and PMMA-transferred graphene. A total of 225 Raman spectra were taken from each type of transferred graphene. The yellow star represents the G and 2D peak positions of the pristine graphene with neither doping nor strain. f 2D peak’s full width at half maximum ( Γ 2D ) of GSE- and PMMA-transferred graphene. The solid lines are fitting lines of distribution function for Γ 2D .

Article Snippet: As shown in Fig. , the integrated graphene emitter device arrays with 4-inch GSE-transferred graphene wafer were successfully obtained.

Techniques:

Journal: Nature Communications

Article Title: Integrated wafer-scale ultra-flat graphene by gradient surface energy modulation

doi: 10.1038/s41467-022-33135-w

Figure Lengend Snippet: a Transfer characteristics comparison of two typical Hall-bar devices fabricated with PMMA- and GSE-transferred graphene. Inset: image of graphene Hall-bar device on SiO 2 /Si. b Histograms of FET mobility of GSE- and PMMA-transferred graphene. The average mobility of 42 GSE-transferred and 18 PMMA-transferred graphene devices are 6000 cm 2 V −1 s −1 and 2000 cm 2 V −1 s −1 , respectively. c The change in Hall resistance as a function of magnetic field of GSE-transferred graphene on SiO 2 /Si at different temperature. Inset: image of graphene Hall-bar device on SiO 2 /Si. d The fabrication scheme of h-BN-encapsulated transferred graphene. e The change in Hall resistance as a function of magnetic field ( B ) of h-BN-encapsulated transferred graphene at 300 K. Inset: image of h-BN encapsulated graphene Hall-bar device. f The variation in Hall resistance ( R xy ) (left axis) and longitudinal resistance ( R xx ) (right axis) as a function of B at 1.7 K. g R xx (left axis) and R xy (right axis) as a function of the back gate ( V g ) at 1.7 K and 8.5 T. h 2D contour plot of R xx as a function of B and V g . The dash black lines show LLs at filling factors ν = ±2, ±6, and ±10, as well as some new emerging fractional filling factors ν = 2/3, ±4/3, 7/3, ±8/3…, due to the degeneracy lifting of LLs.

Article Snippet: As shown in Fig. , the integrated graphene emitter device arrays with 4-inch GSE-transferred graphene wafer were successfully obtained.

Techniques: Comparison

Journal: Nature Communications

Article Title: Integrated wafer-scale ultra-flat graphene by gradient surface energy modulation

doi: 10.1038/s41467-022-33135-w

Figure Lengend Snippet: a A schematic diagram of graphene thermal emitter. b Wafer-scale graphene thermal emitter arrays on GSE-transferred graphene. c Optical microscopy image of 8 × 8 graphene thermal emitters. Inset: single graphene thermal emitter device. d Image of thermal emission at P = 3.0 kW cm −2 captured by IR camera with false-color treatment. The bright spot in the center represents the radiation emitted by graphene. The blue dashed line and yellow dashed line indicate the graphene and metal electrodes, respectively. e Emission spectra issued from a graphene emitter at P = 1.2–7.7 kW cm −2 . f Graphene lattice temperatures obtained by the shift in 2D peak’s position. The temperatures varied approximately linearly with power density. Error bars indicate standard deviations of temperatures at different power density.

Article Snippet: As shown in Fig. , the integrated graphene emitter device arrays with 4-inch GSE-transferred graphene wafer were successfully obtained.

Techniques: Microscopy