Spatial Control of Laser-Induced Doping Profiles in Graphene on Hexagonal Boron Nitride

Neumann, Christoph; Rizzi, Leo; Reichardt, Sven; Terrés, Bernat; Khodkov, Tymofiy; Watanabe, Kenji; Taniguchi, Takashi; Beschoten, Bernd; Stampfer, Christoph

doi:10.1021/acsami.6b01727

Cited by 24 publications

(43 citation statements)

References 32 publications

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“…[31] Figure 2b manifests the Raman spectrum of single layer graphene (Gr) demonstrating the characteristic G and 2D peaks at %1587.8 and %2685.9 cm À1 , respectively. [34,35] Recently, an impressive effort has been made to connect FM metals to the very tiny non-ferromagnetic 2D crystals. When this ratio is greater than 2, it corresponds to single layer graphene, however ratio smaller than 2 indicates bilayer graphene.…”

Section: Resultsmentioning

confidence: 99%

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Spin Valve Effect of 2D‐Materials Based Magnetic Junctions

Iqbal

Siddique

Hussain³

2017

Adv Eng Mater

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The magnetotransport properties of spin valve structure are highly influenced by the type of intervening layer inserted between the ferromagnetic electrodes. In this scenario, spin filtering effect at the interfaces plays a crucial role in determining the magnetoresistance (MR) of such magnetic structures, which can be enhanced by using a suitable intervening layer. Here, the authors investigate the spin filtering effect of the two-dimensional layers such as hexagonal boron nitride (hBN), graphene (Gr), and Gr-hBN hybrid system for modifying the magnetotransport characteristics of the vertical spin valve architectures (Ni/hBN/Ni, Ni/Gr/Ni, and Ni/Gr-hBN/Ni). Compared to graphene, hBN incorporated magnetic junction reveals higher MR and spin polarizations (P) suggesting better spin filtering at the interfaces. The MR for hBN incorporated junction is calculated to be %0.83%, while that of graphene junction it is estimated to be %0.16%. Similar contrast is observed in the 'P' of ferromagnets (FMs) for the two junctions, that is, %6.4% for hBN based magnetic junction and %2.8% for graphene device. However, for Gr-hBN device, the signal not only get inverts, but it also suggests efficient spin filtering mechanism at the FM interfaces. Their results can be useful to comprehend the origin of spin filtering and the choice of non-magnetic spacer for magnetotransport characteristics.

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Section: Resultsmentioning

confidence: 99%

“…Moreover, peak at 1369 cm À1 shows the presence of hBN. [34,35] Recently, an impressive effort has been made to connect FM metals to the very tiny non-ferromagnetic 2D crystals. [36][37][38][39][40][41][42][43][44][45] The basic purpose of this is to take the advantage of electron spin for device applications.…”

Section: Resultsmentioning

confidence: 99%

Spin Valve Effect of 2D‐Materials Based Magnetic Junctions

Iqbal

Siddique

Hussain³

2017

Adv Eng Mater

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“…This particular method of producing van der Waals heterostructures from CVD graphene leads to extremely clean graphene samples with very low doping and extremely high electronic quality, indistinguishable from state‐of‐the‐art exfoliated samples . We compare our results obtained on the hBN‐Gr‐WSe 2 sample, with measurements taken on an hBN‐Gr‐hBN stack that is fabricated using mechanically exfoliated graphene by a wet chemistry‐free transfer process , resulting in similarly clean graphene samples with outstanding electronic quality . In general, both hBN and WSe 2 are known to be very suitable substrates for graphene leading to very flat graphene layers with high charge carrier mobilities .…”

Section: Measurements and Discussionmentioning

confidence: 98%

Line shape of the Raman 2D peak of graphene in van der Waals heterostructures

Neumann

Banszerus

Schmitz

et al. 2016

Physica Status Solidi (b)

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The Raman 2D line of graphene is widely used for device characterization and during device fabrication as it contains valuable information on, e.g., the direction and magnitude of mechanical strain and doping. Here, we present systematic asymmetries in the 2D line shape of exfoliated graphene and graphene grown by chemical vapor deposition. Both graphene crystals are fully encapsulated in van der Waals heterostructures, where hexagonal boron nitride and tungsten diselenide are used as substrate materials. In both material stacks, we find very low doping values and extremely homogeneous strain distributions in the graphene crystal, which is a hall mark of the outstanding electronic quality of these samples. By fitting double Lorentzian functions to the spectra to account for the contributions of inner and outer processes to the 2D peak, we find that the splitting of the sub‐peaks, 6.6±0.5cm−1 (hBN‐Gr‐WSe2) and 8.9±1.0cm−1 (hBN‐Gr‐hBN), is significantly lower than the values reported in previous studies on suspended graphene.

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“…[ 8,9 ] It is generally accepted that an electron transfer via these states leads to a charging of trap states (see red arrow in Figure a), although it is still under debate if these trap states are located either in the bulk of the hBN layer, the hBN‐to‐2D‐material interface, or even the hBN‐to‐substrate interface. [ 10–14 ] Independent on their exact position, these charged defects partially screen the gate‐electric field (see the result in Figure 1b), which in turn will change the effective gate‐induced charge carrier density in the 2D material.…”

Section: Figurementioning

confidence: 99%

How Photoinduced Gate Screening and Leakage Currents Dynamically Change the Fermi Level in 2D Materials

Volmer

Ersfeld

Rathmann

et al. 2020

Physica Rapid Research Ltrs

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One important goal in the field of 2D materials is the investigation of valley physics in semiconducting transition metal dichalcogenides (TMDs). [1,2] As valley dynamics are governed by a delicate interplay of different electron-electron, electronphonon, and many-body interactions, an overall understanding of valley physics is only possible, and physical models can only be tested when different device properties such as valley lifetimes, exciton lifetimes, spin and momentum scattering times, or phonon and electron dispersion relations are analyzed as a function of Fermi level position-ideally for the same device. To accomplish this, a variety of different measurements are required, most importantly, the combination of both optical and electrical techniques, e.g., only the combination of gate-dependent electrical transport measurements, photoluminescence (PL) spectroscopy, and time-resolved Kerr rotation (TRKR) measurements recently enabled us to identify the dynamics which are responsible for the transfer of a polarization from optically excited bright trions to a valley polarization of free charge carriers in monolayer WSe 2. [3] However, this necessary prerequisite for the investigation of valley physics encounters practical obstacles, as not every measurement system can simultaneously conduct optical and electrical measurements. Even worse is the fact that some measurement techniques are mutually exclusive, e.g., in valley-sensitive TRKR measurements, the pump and probe energies normally have to be set to neutral or charged exciton energies (i.e., energies below the band gap), [3-5] but for this, first PL measurements with above-bandgap excitation are necessary to determine the energetic position of these exciton features. [6,7] Therefore, it is important to compare gate-dependent measurements recorded under different conditions.

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Spatial Control of Laser-Induced Doping Profiles in Graphene on Hexagonal Boron Nitride

Cited by 24 publications

References 32 publications

Spin Valve Effect of 2D‐Materials Based Magnetic Junctions

Spin Valve Effect of 2D‐Materials Based Magnetic Junctions

Line shape of the Raman 2D peak of graphene in van der Waals heterostructures

How Photoinduced Gate Screening and Leakage Currents Dynamically Change the Fermi Level in 2D Materials

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