Direct observation of charge transfer region at interfaces in graphene devices

Nagamura, Naoka; Horiba, Koji; Toyoda, Satoshi; Kurosumi, Shodai; Shinohara, T.; Oshima, Masaharu; Fukidome, Hirokazu; Suemitsu, Maki; Nagashio, Kosuke; Toriumi, Akira

doi:10.1063/1.4808083

Cited by 32 publications

(39 citation statements)

References 31 publications

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“…The binding energy scale was calibrated using the photoelectron peaks of a gold mesh foil (Au 4f 7/2, binding energy: 84.0 eV) at the same potential as the source electrode, and the Fermi levels detected in valence spectra on Ni electrodes. Details of the experimental setup can be found elsewhere 19,22 . The resistance-gate voltage characteristics were evaluated in ambient air conditions using a semiconductor parameter analyzer (B1500A, Keysight Technologies Inc.).…”

Section: Sample Characterizationmentioning

confidence: 99%

Influence of interface dipole layers on the performance of graphene field effect transistors

Nagamura

Fukidome

Nagashio

et al. 2019

Carbon

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The linear band dispersion of graphene's bands near the Fermi level gives rise to its unique electronic properties, such as a giant carrier mobility, and this has triggered extensive research in applications, such as graphene field-effect transistors (GFETs). However, GFETs generally exhibit a device performance much inferior compared to the expected one. This has been attributed to a strong dependence of the electronic properties of graphene on the surrounding interfaces. Here we study the interface between a graphene channel and SiO2, and by means of photoelectron spectromicroscopy achieve a detailed determination of the course of band alignment at the interface. Our results show that the electronic properties of graphene are modulated by a hydrophilic SiO2 surface, but not by a hydrophobic one. By combining photoelectron spectromicroscopy with GFET transport property characterization, we demonstrate that the presence of electrical dipoles in the interface, which reflects the SiO2 surface electrochemistry, determines the GFET device performance. A hysteresis in the resistance vs. gate voltage as a function of polarity is ascribed to a reversal of the dipole layer by the gate voltage. These data pave the way for GFET device optimization.

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Section: Sample Characterizationmentioning

confidence: 99%

Influence of interface dipole layers on the performance of graphene field effect transistors

Nagamura

Fukidome

Nagashio

et al. 2019

Carbon

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“…6(b), indicating that the direct tunnelling process is unlikely to occur. In this profile, the interfacial region between the contact and the gated channel is simplified to be linear, and measures 0.5 µm in length, which is typical for metal contacts on single layer graphene [35]; the estimation was performed based on the under-contact ΔEF of 0.14 eV of hole doping and VG of VNP + 40 V. The thermally activated tunnelling width is dependent on the thermal excitation energy. Figure 6(c) shows the thermally activated 9 tunnelling width as a function of the thermal excitation energy.…”

Section: (A)mentioning

confidence: 99%

Contact resistance at planar metal contacts on bilayer graphene and effects of molecular insertion layers

Nouchi

2017

Nanotechnology

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The possible origins of metal-bilayer graphene (BLG) contact resistance are investigated by taking into consideration the bandgap formed by interfacial charge transfer at the metal contacts.Our results show that a charge injection barrier (Schottky barrier) does not contribute to the contact resistance because the BLG under the contacts is always degenerately doped. We also showed that the contact-doping-induced increase in the density of states (DOS) of BLG under the metal contacts decreases the contact resistance owing to enhanced charge carrier tunnelling at the contacts. The contact doping can be enhanced by inserting molecular dopant layers into the metal contacts. However, carrier tunnelling through the insertion layer increases the contact resistance, and thus, alternative device structures should be employed. Finally, we showed that the inter-band transport by variable range hopping via in-gap states is the largest contributor to contact resistance when the carrier type of the gated channel is opposite to the contact doping carrier type. This indicates that the strategy of contact resistance reduction by the contact-doping-induced increase in the DOS is effective only for a single channel transport branch (n-or p-type) depending on the contact doping carrier type. 2

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“…The interface chemical composition is probed nanoscopically by using three-dimensional high-resolution scanning photoelectron microscopy (3D nano-ESCA (electron spectroscopy for chemical analysis)) using a focused incident X-ray beam with a diameter of 70 nm and a photon energy of 1000 eV3031. The energy resolution of the spectrometer was set to 300 meV32.…”

Section: Resultsmentioning

confidence: 99%

Microscopically-Tuned Band Structure of Epitaxial Graphene through Interface and Stacking Variations Using Si Substrate Microfabrication

Fukidome

Ide

Kawai

et al. 2014

Sci Rep

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Graphene exhibits unusual electronic properties, caused by a linear band structure near the Dirac point. This band structure is determined by the stacking sequence in graphene multilayers. Here we present a novel method of microscopically controlling the band structure. This is achieved by epitaxy of graphene on 3C-SiC(111) and 3C-SiC(100) thin films grown on a 3D microfabricated Si(100) substrate (3D-GOS (graphene on silicon)) by anisotropic etching, which produces Si(111) microfacets as well as major Si(100) microterraces. We show that tuning of the interface between the graphene and the 3C-SiC microfacets enables microscopic control of stacking and ultimately of the band structure of 3D-GOS, which is typified by the selective emergence of semiconducting and metallic behaviours on the (111) and (100) portions, respectively. The use of 3D-GOS is thus effective in microscopically unlocking various potentials of graphene depending on the application target, such as electronic or photonic devices.

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Direct observation of charge transfer region at interfaces in graphene devices

Cited by 32 publications

References 31 publications

Influence of interface dipole layers on the performance of graphene field effect transistors

Influence of interface dipole layers on the performance of graphene field effect transistors

Contact resistance at planar metal contacts on bilayer graphene and effects of molecular insertion layers

Microscopically-Tuned Band Structure of Epitaxial Graphene through Interface and Stacking Variations Using Si Substrate Microfabrication

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