Open-Atmosphere Flame Synthesis of Monolayer Graphene

In this work we have critically reviewed the processes in high-temperature sublimation growth of graphene in Ar atmosphere using closed graphite crucible. Special focus is put on buffer layer formation and free charge carrier properties of monolayer graphene and quasi-freestanding monolayer graphene on 4H–SiC. We show that by introducing Ar at higher temperatures, TAr, one can shift the formation of the buffer layer to higher temperatures for both n-type and semi-insulating substrates. A scenario explaining the observed suppressed formation of buffer layer at higher TAr is proposed and discussed. Increased TAr is also shown to reduce the sp3 hybridization content and defect densities in the buffer layer on n-type conductive substrates. Growth on semi-insulating substrates results in ordered buffer layer with significantly improved structural properties, for which TAr plays only a minor role. The free charge density and mobility parameters of monolayer graphene and quasi-freestanding monolayer graphene with different TAr and different environmental treatment conditions are determined by contactless terahertz optical Hall effect. An efficient annealing of donors on and near the SiC surface is suggested to take place for intrinsic monolayer graphene grown at 2000 ∘C, and which is found to be independent of TAr. Higher TAr leads to higher free charge carrier mobility parameters in both intrinsically n-type and ambient p-type doped monolayer graphene. TAr is also found to have a profound effect on the free hole parameters of quasi-freestanding monolayer graphene. These findings are discussed in view of interface and buffer layer properties in order to construct a comprehensive picture of high-temperature sublimation growth and provide guidance for growth parameters optimization depending on the targeted graphene application.

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Structure-mediated thermal transport of monolayer graphene allotropes nanoribbons

Carbon ◽

10.1016/j.carbon.2014.05.045 ◽

2014 ◽

Vol 77 ◽

pp. 416-423 ◽

Cited By ~ 27

Author(s):

Haifei Zhan ◽

Yingyan Zhang ◽

John M. Bell ◽

Yiu-Wing Mai ◽

Yuantong Gu

Keyword(s):

Thermal Transport ◽

Monolayer Graphene

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Smart optical cross dipole nanoantenna with multibeam pattern

Scientific Reports ◽

10.1038/s41598-021-84495-0 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Seyyed Mohammad Mehdi Moshiri ◽

Najmeh Nozhat

Keyword(s):

Radiation Pattern ◽

Chemical Potential ◽

Monolayer Graphene ◽

Absorption Characteristic ◽

Radiation Beam ◽

Directional Radiation ◽

Chemical Potentials ◽

Different Types ◽

Absorption Power ◽

Maximum Directivity

AbstractIn this paper, an optical smart multibeam cross dipole nano-antenna has been proposed by combining the absorption characteristic of graphene and applying different arrangements of directors. By introducing a cross dipole nano-antenna with two V-shaped coupled elements, the maximum directivity of 8.79 dBi has been obtained for unidirectional radiation pattern. Also, by applying various arrangements of circular sectors as director, different types of radiation pattern such as bi- and quad-directional have been attained with directivities of 8.63 and 8.42 dBi, respectively, at the wavelength of 1550 nm. The maximum absorption power of graphene can be tuned by choosing an appropriate chemical potential. Therefore, the radiation beam of the proposed multibeam cross dipole nano-antenna has been controlled dynamically by applying a monolayer graphene. By choosing a suitable chemical potential of graphene for each arm of the suggested cross dipole nano-antenna without the director, the unidirectional radiation pattern shifts ± 13° at the wavelength of 1550 nm. Also, for the multibeam nano-antenna with different arrangements of directors, the bi- and quad-directional radiation patterns have been smartly modified to uni- and bi-directional ones with the directivities of 10.1 and 9.54 dBi, respectively. It is because of the graphene performance as an absorptive or transparent element for different chemical potentials. This feature helps us to create a multipath wireless link with the capability to control the accessibility of each receiver.

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