Resolving mobility anisotropy in quasi-free-standing epitaxial graphene by terahertz optical Hall effect

Armakavicius, Nerijus; Kühne, Philipp; Eriksson, Jens; Bouhafs, Chamseddine; Stanishev, V.; Ivanov, Ivan Gueorguiev; Yakimova, Rositsa; Zakharov, Alexei; Al-Temimy, Ameer; Coletti, Camilla; Schubert, Mathias; Darakchieva, Vanya

doi:10.1016/j.carbon.2020.09.035

Cited by 7 publications

(6 citation statements)

References 68 publications

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“…The mobility parameters were found to be slightly anisotropic in accordance with our recent study[20]. The anisotropy, which is caused by the substrate step edges, does not have any baring on the results discussed in the current work.…”

supporting

confidence: 92%

“…However, exposure to ambient can cause environmental doping of graphene via an acceptor redox reaction at the surface of the graphene involving various environmental gases (O 2 , H 2 O, and CO 2 ), which results in electron withdrawal [48]. Consequently, MLG can exhibit p-type conductivity depending on sample history [20,49]. We have previously shown that the THz OHE is an excellent tool to precisely determine free charge carrier density and mobility parameters of graphene and monitor their in-situ variation under the influence of different gases [20,31,34,50].…”

Section: Free Charge Carrier Properties Of Mlg and Qfs-mlgmentioning

confidence: 99%

“…Consequently, MLG can exhibit p-type conductivity depending on sample history [20,49]. We have previously shown that the THz OHE is an excellent tool to precisely determine free charge carrier density and mobility parameters of graphene and monitor their in-situ variation under the influence of different gases [20,31,34,50]. In order to determine the intrinsic properties of MLG and QFS-MLG, prior to the measurements they were annealed in vacuum (10 −6 mbar) at 1000 • C and 500 • C, 2 respectively.…”

Section: Free Charge Carrier Properties Of Mlg and Qfs-mlgmentioning

confidence: 99%

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Critical View on Buffer Layer Formation and Monolayer Graphene Properties in High-Temperature Sublimation

Stanishev¹,

Armakavicius²,

Bouhafs³

et al. 2021

Preprint

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In this work we have critically reviewed the processes in high-temperature sublimation growth of graphene in Ar atmosphere using enclosed graphite crucible. Special focus is put on buffer layer formation and free charge carrier properties of monolayer graphene and quasi-freestanding monolayer garphene on 4H-SiC. We show that by introducing Ar at different temperatures, TAr one can shift to higher temperatures the formation of the buffer layer for both n-type and semi-insulating substrates. A scenario explaining the observed suppresed 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 takes place in 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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supporting

confidence: 92%

Section: Free Charge Carrier Properties Of Mlg and Qfs-mlgmentioning

confidence: 99%

Section: Free Charge Carrier Properties Of Mlg and Qfs-mlgmentioning

confidence: 99%

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Critical View on Buffer Layer Formation and Monolayer Graphene Properties in High-Temperature Sublimation

Stanishev¹,

Armakavicius²,

Bouhafs³

et al. 2021

Preprint

Self Cite

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“…However, also there, an increase in RH leads to a decrease in response. The appearance of sensitivity for IEG compared to PEG is most probably due to the known increased defect density for IEG (compare [134] and section 4.2.4). Another possible explanation could be the difference in carrier density between the sensors [134].…”

Section: Gas Measurementsmentioning

confidence: 96%

“…The appearance of sensitivity for IEG compared to PEG is most probably due to the known increased defect density for IEG (compare [134] and section 4.2.4). Another possible explanation could be the difference in carrier density between the sensors [134]. The response of the IEG sensor is comparably small (see also Figure 4.15), but still has estimated LODs of 0.68 and 1.40 ppb for C6H6 at 0 and 50 %RH.…”

Section: Gas Measurementsmentioning

confidence: 96%

Functionalized epitaxial graphene as versatile platform for air quality sensors

Rodner

2021

Linköping Studies in Science and Technology. Dissertations

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The work presented in this thesis focuses on epitaxial graphene on SiC as a platform for air quality sensors. Several approaches have been tested and evaluated to increase the sensitivity, selectivity, speed of response and stability of the sensors. The graphene surfaces have been functionalized, for example, with different metal oxide nanoparticles and nanolayers using hollow-cathode sputtering and pulsed laser deposition. The modified surfaces were investigated towards topography, integrity and chemical composition with characterization methods such as atomic force microscopy and Raman spectroscopy. Interaction energies between several analytes and nanoparticle-graphene-combinations were calculated by density functional theory to find the optimal material for specific target gases, and to verify the usefulness of this approach. The impact of environmental influences such as operating temperature, relative humidity and UV irradiation on sensing properties was investigated as well. To further enhance sensor performances, the first-order time-derivative of the sensor's resistance was introduced to speed up sensor response and a temperature cycled operation mode was investigated towards selectivity.Applying these methods in laboratory conditions, sensors with a quantitative readout of single ppb benzene and formaldehyde were developed. These results show promise to fill the existing gap of low-cost but highly sensitive and fast gas sensors for air quality monitoring.The present dissertation thesis is the result of my binational doctoral studies carried out between November 2016 and May 2021.

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Elucidating the electronic and magnetic properties of epitaxial graphene grown on SiC with a defective buffer layer

2021

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Resolving mobility anisotropy in quasi-free-standing epitaxial graphene by terahertz optical Hall effect

Cited by 7 publications

References 68 publications

Critical View on Buffer Layer Formation and Monolayer Graphene Properties in High-Temperature Sublimation

Critical View on Buffer Layer Formation and Monolayer Graphene Properties in High-Temperature Sublimation

Functionalized epitaxial graphene as versatile platform for air quality sensors

Elucidating the electronic and magnetic properties of epitaxial graphene grown on SiC with a defective buffer layer

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