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Experimental demonstration of a transparent graphene millimetre wave absorber with 28% fractional bandwidth at 140 GHz.

Wu B, Tuncer HM, Naeem M, Yang B, Cole MT, Milne WI, Hao Y - Sci Rep (2014)

Bottom Line: Broadband absorption is a result of mutually coupled Fabry-Perot resonators represented by each graphene-quartz substrate.Millimetre wave reflectometer measurements of the stacked graphene-quartz absorbers demonstrated excellent broadband absorption of 90% with a 28% fractional bandwidth from 125-165 GHz.Our data suggests that the absorbers' operation can also be extended to microwave and low-terahertz bands with negligible loss in performance.

View Article: PubMed Central - PubMed

Affiliation: 1] School of Electronic Engineering and Computer Science, Queen Mary University of London, London, E1 4NS, United Kingdom [2] School of Electronic Engineering, Xidian University, Xi'an, 710071, China.

ABSTRACT
The development of transparent radio-frequency electronics has been limited, until recently, by the lack of suitable materials. Naturally thin and transparent graphene may lead to disruptive innovations in such applications. Here, we realize optically transparent broadband absorbers operating in the millimetre wave regime achieved by stacking graphene bearing quartz substrates on a ground plate. Broadband absorption is a result of mutually coupled Fabry-Perot resonators represented by each graphene-quartz substrate. An analytical model has been developed to predict the absorption performance and the angular dependence of the absorber. Using a repeated transfer-and-etch process, multilayer graphene was processed to control its surface resistivity. Millimetre wave reflectometer measurements of the stacked graphene-quartz absorbers demonstrated excellent broadband absorption of 90% with a 28% fractional bandwidth from 125-165 GHz. Our data suggests that the absorbers' operation can also be extended to microwave and low-terahertz bands with negligible loss in performance.

No MeSH data available.


Related in: MedlinePlus

Schematic and optical images of multilayer graphene on quartz and stacked graphene-quartz absorbers.(a) Schematic of the multiple transfer-etch processing for a 2 L device; (b) Typical UV-Vis spectra for the 1.3 mm thick bare quartz and 1–4 L graphene samples; (c) Schematic of the N-unit stacked absorber and the equivalent transmission-line circuit model; (d) Optical images of 2 L and 3 L absorbers and N = 1–4 stacked graphene-quartz structures backed with a ground plate (N is the number of stacked graphene-quartz units).
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f1: Schematic and optical images of multilayer graphene on quartz and stacked graphene-quartz absorbers.(a) Schematic of the multiple transfer-etch processing for a 2 L device; (b) Typical UV-Vis spectra for the 1.3 mm thick bare quartz and 1–4 L graphene samples; (c) Schematic of the N-unit stacked absorber and the equivalent transmission-line circuit model; (d) Optical images of 2 L and 3 L absorbers and N = 1–4 stacked graphene-quartz structures backed with a ground plate (N is the number of stacked graphene-quartz units).

Mentions: CVD graphene films were grown on four inch Cu/SiO2/Si wafers and were found, by optical and electron microscopy to be free of pin-holes. Samples were of high uniformity with >90% monolayer coverage, as confirmed by Raman spectroscopic mapping and optical microscopy36. Films were transferred to fused silica quartz substrates using spin-coated 200 nm thick poly (methyl methacrylate) (PMMA) as the supporting layer (for details see Methods section) (Fig. 1a). Multilayer graphene samples were processed by a multiple transfer-and-etch method. This involves repetitive transfer of the PMMA-graphene films onto diced graphene on Cu/SiO2/Si substrates and etching them in an aqueous ammonium persulfate solution before finally transferring the released PMMA/graphene onto the quartz substrates. This method avoids significant PMMA residue build-up between the stacks of graphene layers yielding reduced mean sheet resistance of ~0.9 kΩ/sq for 2 L and ~0.6 kΩ/sq for 3 L. The number of graphene layers was confirmed via UV-Vis spectro-photometery. Optical transmittances of 85%–91% at 700 nm for quartz-supported 1–4 L graphene was noted (Fig. 1b).


Experimental demonstration of a transparent graphene millimetre wave absorber with 28% fractional bandwidth at 140 GHz.

Wu B, Tuncer HM, Naeem M, Yang B, Cole MT, Milne WI, Hao Y - Sci Rep (2014)

Schematic and optical images of multilayer graphene on quartz and stacked graphene-quartz absorbers.(a) Schematic of the multiple transfer-etch processing for a 2 L device; (b) Typical UV-Vis spectra for the 1.3 mm thick bare quartz and 1–4 L graphene samples; (c) Schematic of the N-unit stacked absorber and the equivalent transmission-line circuit model; (d) Optical images of 2 L and 3 L absorbers and N = 1–4 stacked graphene-quartz structures backed with a ground plate (N is the number of stacked graphene-quartz units).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3928574&req=5

f1: Schematic and optical images of multilayer graphene on quartz and stacked graphene-quartz absorbers.(a) Schematic of the multiple transfer-etch processing for a 2 L device; (b) Typical UV-Vis spectra for the 1.3 mm thick bare quartz and 1–4 L graphene samples; (c) Schematic of the N-unit stacked absorber and the equivalent transmission-line circuit model; (d) Optical images of 2 L and 3 L absorbers and N = 1–4 stacked graphene-quartz structures backed with a ground plate (N is the number of stacked graphene-quartz units).
Mentions: CVD graphene films were grown on four inch Cu/SiO2/Si wafers and were found, by optical and electron microscopy to be free of pin-holes. Samples were of high uniformity with >90% monolayer coverage, as confirmed by Raman spectroscopic mapping and optical microscopy36. Films were transferred to fused silica quartz substrates using spin-coated 200 nm thick poly (methyl methacrylate) (PMMA) as the supporting layer (for details see Methods section) (Fig. 1a). Multilayer graphene samples were processed by a multiple transfer-and-etch method. This involves repetitive transfer of the PMMA-graphene films onto diced graphene on Cu/SiO2/Si substrates and etching them in an aqueous ammonium persulfate solution before finally transferring the released PMMA/graphene onto the quartz substrates. This method avoids significant PMMA residue build-up between the stacks of graphene layers yielding reduced mean sheet resistance of ~0.9 kΩ/sq for 2 L and ~0.6 kΩ/sq for 3 L. The number of graphene layers was confirmed via UV-Vis spectro-photometery. Optical transmittances of 85%–91% at 700 nm for quartz-supported 1–4 L graphene was noted (Fig. 1b).

Bottom Line: Broadband absorption is a result of mutually coupled Fabry-Perot resonators represented by each graphene-quartz substrate.Millimetre wave reflectometer measurements of the stacked graphene-quartz absorbers demonstrated excellent broadband absorption of 90% with a 28% fractional bandwidth from 125-165 GHz.Our data suggests that the absorbers' operation can also be extended to microwave and low-terahertz bands with negligible loss in performance.

View Article: PubMed Central - PubMed

Affiliation: 1] School of Electronic Engineering and Computer Science, Queen Mary University of London, London, E1 4NS, United Kingdom [2] School of Electronic Engineering, Xidian University, Xi'an, 710071, China.

ABSTRACT
The development of transparent radio-frequency electronics has been limited, until recently, by the lack of suitable materials. Naturally thin and transparent graphene may lead to disruptive innovations in such applications. Here, we realize optically transparent broadband absorbers operating in the millimetre wave regime achieved by stacking graphene bearing quartz substrates on a ground plate. Broadband absorption is a result of mutually coupled Fabry-Perot resonators represented by each graphene-quartz substrate. An analytical model has been developed to predict the absorption performance and the angular dependence of the absorber. Using a repeated transfer-and-etch process, multilayer graphene was processed to control its surface resistivity. Millimetre wave reflectometer measurements of the stacked graphene-quartz absorbers demonstrated excellent broadband absorption of 90% with a 28% fractional bandwidth from 125-165 GHz. Our data suggests that the absorbers' operation can also be extended to microwave and low-terahertz bands with negligible loss in performance.

No MeSH data available.


Related in: MedlinePlus