Electrical transport and low-temperature scanning tunneling microscopy of microsoldered graphene

Герингер, Виктор; Subramaniam, Dinesh; Michel, Ann‐Katrin U.; Szafranek, B. N.; Schall, Daniel; Georgi, A.; Mashoff, T.; Neumaier, Daniel; Liebmann, Marcus; Morgenstern, Markus

doi:10.1063/1.3334730

Cited by 45 publications

(43 citation statements)

References 31 publications

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“…However, when graphene is deposited on an insulating substrate such as SiO 2 its properties are modified due to defects, strain, inhomogeneous doping and trapped charges [16][17][18] . These altering effects are responsible for a wide range of non-intrinsic spectra reported in the literature for graphene samples deposited on SiO 2 substrates 16,17,19 .…”

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confidence: 99%

Quantized Landau level spectrum and its density dependence in graphene

2011

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Scanning tunneling microscopy and spectroscopy in magnetic field was used to study Landau quantization in graphene and its dependence on charge carrier density. Measurements were carried out on exfoliated graphene samples deposited on a chlorinated SiO 2 thermal oxide which allowed observing the Landau level sequences characteristic of single layer graphene while tuning the density through the Si backgate. Upon changing the carrier density we find abrupt jumps in the Fermi level after each Landau level is filled. Moreover, the Landau level spacing shows a marked increase at low doping levels, consistent with an interaction-induced renormalization of the Dirac cone. One of the hallmarks of the relativistic charge carriers 1,2 in graphene is the appearance in a magnetic field of an unusual Landau level (LL) at zero energy which reflects the chiral symmetry of the low lying excitations. The presence of this LL has been inferred in magnetotransport measurements employing the standard configuration of graphene supported on SiO 2 3,4 from the conspicuous absence of a quantum Hall plateau at zero filling-factor. Remarkably because in graphene the carriers reside right at the surface, the LLs (including the LL at zero-energy) can be accessed directly through scanning tunneling spectroscopy (STS) as was demonstrated in studies of graphene samples supported on the surface of graphite 5,6 .However, the LLs were not observed in STS measurements on graphene samples supported on insulating substrates which allow control of the carrier density through gating. This is because due to the purely two dimensional nature of graphene, substrate induced potential fluctuations obscure the intrinsic physics of the charge carriers close to the Dirac point.One way to overcome this limitation is to use suspended samples 7,8 where transport measurements have shown that in the absence of the substrate the intrinsic Dirac point physics including interaction effects is revealed 9,10 . The use of suspended samples is however limited due to their fragility, small size and reduced range of gating. Finding a minimally invasive insulating substrate on which graphene can be gated and also visualized is therefore of great interest.By using scanning tunneling microscopy (STM) and spectroscopy (STS) we show that for graphene supported on SiO 2 substrates which were treated by chlorination to minimize trapped charges and in sufficiently large magnetic fields, the LL sequence specific to single layer graphene and its dependence on carrier density can be accessed. Upon varying the carrier-density sudden jumps of the Fermi-energy are observed after filling each LL. Moreover the measured density-dependence of the LL spacing shows a rapid increase upon approaching the Dirac-point, consistent with an interaction-induced renormalization of the Dirac cone.A simple method for preparing high quality graphene samples is mechanical exfoliation from graphite followed by deposition on the surface of SiO 2 capping a Si crystal 3 . This relative ease of samp...

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confidence: 99%

Quantized Landau level spectrum and its density dependence in graphene

2011

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“…In figure 3, the measured graphene channel resistance (R) as a function of back gate voltage bias (V BG ) is shown with Si substrate used as the back gate for the GFET. The Dirac point (V Dirac ) of the CVD-assembled graphene on h-BN exhibits weak n-type doping possibly due to the PMMA residue introduced during the graphene transfer process [10]. Figure 4 shows the graphene inverter composed of a pair of two GFETs and schematic view.…”

Section: Experimental Results and Analysismentioning

confidence: 99%

CVD-Graphene Complementary Logic on Ultra-thin Multilayer Hexagonal Boron Nitride

Kim

Jain

et al. 2012

MRS Proc.

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Graphene, a two-dimensional carbon allotrope, has raised great interests as a material candidate for future electronics due to its superb carrier transport and unique physics. The demand for future-generation large-scale carbon-based electronics motivates assembly of largearea graphene and selection of ideal substrate material that best preserves the transport property of graphene. In this work, CVD-assembled large-area graphene on thin multilayer hexagonal boron nitride (h-BN) is employed to demonstrate the basic building block of digital circuitinverter prototype made of two graphene-channel field-effect transistors (GFETs). The doping in the CVD-grown graphene, probed via electrical measurements, is implemented through nonuniform local surface chemistry. The full transfer response of the graphene logic inverter is demonstrated in the localized P/N doping region.

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“…11.2 (b). Previous study using scanning tunneling microscopy has shown that this thin layer of PMMA residue typically has a thickness of 1 to 2 nm (Geringer et al ., 2010 ). Generally, an increase of transfer or lithography times causes more PMMA to accumulate on the graphene.…”

Section: Transfer-induced Metal and Molecule Adsorptionsmentioning

confidence: 98%