Electrical transport properties of graphene on SiO2 with specific surface structures

Nagashio, Kosuke; Yamashita, Tadahiro; Nishimura, Tomonori; Kita, Koji; Toriumi, Akira

doi:10.1063/1.3611394

Cited by 185 publications

(187 citation statements)

References 34 publications

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“…The drain-source current is controlled by the back-gate voltage, and bi-polar characteristics with a Dirac point are produced. The electrical properties of the graphene are significantly influenced by its surrounding environment, e.g., the atmosphere, molecules adsorbed on the SiO 2 layer underneath the graphene, [14][15][16] and the oxide interlayer between the metal electrode and graphene. [17][18][19] For instance, water (H 2 O) molecules adsorbed on the graphene surface cause hysteresis in the electrical properties of the transistor.…”

Section: Introductionmentioning

confidence: 99%

Giant Dirac point shift of graphene phototransistors by doped silicon substrate current

et al. 2016

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Graphene is a promising new material for photodetectors due to its excellent optical properties and high-speed response. However, graphene-based phototransistors have low responsivity due to the weak light absorption of graphene. We have observed a giant Dirac point shift upon white light illumination in graphene-based phototransistors with n-doped Si substrates, but not those with p-doped substrates. The source-drain current and substrate current were investigated with and without illumination for both p-type and n-type Si substrates. The decay time of the drain-source current indicates that the Si substrate, SiO2 layer, and metal electrode comprise a metal-oxide-semiconductor (MOS) capacitor due to the presence of defects at the interface between the Si substrate and SiO2 layer. The difference in the diffusion time of the intrinsic major carriers (electrons) and the photogenerated electron-hole pairs to the depletion layer delays the application of the gate voltage to the graphene channel. Therefore, the giant Dirac point shift is attributed to the n-type Si substrate current. This phenomenon can be exploited to realize high-performance graphene-based phototransistors.

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Section: Introductionmentioning

confidence: 99%

Giant Dirac point shift of graphene phototransistors by doped silicon substrate current

et al. 2016

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“…For Sample A, the SiO 2 /Si substrate was annealed at 300 ˚C for 30 min but the Pd anode was not annealed; Sample B: the SiO 2 /Si substrate was annealed at 300 ˚C for 30 min, and after deposition of Pd on the substrate, the sample was annealed at 230 ˚C for 60 min; Sample C: neither the substrate nor the anode was annealed; Sample D: the SiO 2 /Si substrate was not pre-annealed but after deposition of Pd, the sample was annealed at 230 o C for 60 min. It has been found that water molecules bonded to the silanol groups of SiO 2 /Si substrate can be desorbed via annealing at 220 o C, 20 thus the substrate annealing at 300 o C removes moisture and organic adsorbates, thereby improving the uniformity of substrate surface and adhesion of Pd anode.…”

mentioning

confidence: 99%

Effects of substrate and anode metal annealing on InGaZnO Schottky diodes

Yan

et al. 2017

Applied Physics Letters

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By studying different annealing effects of substrate and anode metal, high-performance Schottky diodes based on InGaZnO (IGZO) film have been realized. It is observed that a suitable thermal annealing of the SiO 2 /Si substrate significantly improves the diode performance. In contrary, annealing of the Pd anode increases surface roughness, leading to degradation in the diode performance. As such, by only annealing the substrate but not the anode, we are able to achieve an extremely high rectification ratio of 7.2 × 10 7 , a large barrier height of 0.88 eV, and a near unity ideality factor of 1.09. The diodes exhibit the highest performance amongst IGZO-based Schottky diodes reported to date where IGZO layer is not annealed.The capacitance vs. voltage measurements indicate that the surface roughness is correlated with the trap state density at the Schottky interface.

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“…17 In particular, there are two specific surface structures: the highly polarized hydrophilic silanol group (Si-OH) and the weakly polarized hydrophobic siloxane group (Si-O-Si). Because of the monatomic two-dimensional structure, the "mixed" interaction among the metal, the graphene, and the insulator, which could not be consistent with the sum of two different interactions of metal/grphene and graphene/insulator, should be considered.…”

Section: Effect Of Substrate On the Dirac Point Of Graphenementioning

confidence: 99%

“…The hysteresis in the drain current -back-gate voltage curves, which may be caused by the orientation polarization of water molecules, was not observed because of the hydrophobic nature of the siloxane surface of SiO 2 substrates. 17 Electron-beam lithography was used to pattern electrical contacts onto graphene. The contact metal of Ni with the thickness of ~35 nm was thermally evaporated on resist-patterned graphene and subjected to lift-off with acetone.…”

Section: Device Fabricationmentioning

confidence: 99%

Carrier density modulation in graphene underneath Ni electrode

Moriyama

Nagashio

Nishimura

et al. 2013

Journal of Applied Physics

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We investigate the transport properties of graphene underneath metal to reveal whether the carrier density in graphene underneath source/drain electrodes in graphene field-effect transistors is fixed. The resistance of the graphene/Ni double-layered structure has shown a graphene-like back-gate bias dependence. In other words, the electrical properties of graphene are not significantly affected by its contact with Ni. This unexpected result may be ascribed to resist residuals at the metal/graphene interface, which may reduce the interaction between graphene and metals. In a back-gate device fabricated using the conventional lithography technique with an organic resist, the carrier density modulation in the graphene underneath the metal electrodes should be considered when discussing the metal/graphene contact. 1．IntroductionGraphene is attracting great attention as an alternative material for future high-speed field-effect transistors (FETs) because of its remarkably high carrier mobility. 1 Contact resistance, however, limits the device performance of graphene FETs. [2][3][4][5] To improve the contact resistance, a rigorous understanding of the graphene/metal interface is crucial.Because of its monatomic, two-dimensional structure, graphene is highly sensitive to its environment. In the contact region, the properties of graphene are influenced by the contacting metal. Because of the work function difference between graphene and metals, charge transfer takes place at the interface, resulting in electrical doping in graphene. A photocurrent study has confirmed that this doped region extends hundreds of nanometers from the contact region toward the channel region because of the considerably long screening length resulting from the small density of states (DOS) at the Fermi level. 6 Moreover, the asymmetry in the resistance as a function of the gate voltage is reported to result from the p-n junction formation near the metal electrode. 7 So far, Fermi level of graphene is assumed to be fixed relative to the Dirac point (DP). 6,8 In addition to the charge doping effect, the energy-band alteration in graphene in contact with metals has been considered. A theoretical analysis suggests that the graphene/metal interface can be classified into two groups, an adsorption group (e.g., Au, Ag, Pt) and a chemisorption group (e.g., Ni, Co, Pd). 9,10 At the chemisorption interface, it is predicted that the distance between the metal and graphene is shorter than the interlayer distance in graphite and that the d-orbitals of the metal are strongly hybridized with the p z -orbitals of graphene, 11 resulting in the destruction of the band structure and an increase in the DOS in graphene. The main difference between adsorption and chemisorption metals is the degree of filling in the d-orbitals, which determines the stability of the antibonding states in the hybridization because a large number of electrons in the antibonding states destabilizes the hybridization. 11 Experimentally, the band structure of graphene grown on a Ni substr...

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Electrical transport properties of graphene on SiO2 with specific surface structures

Cited by 185 publications

References 34 publications

Giant Dirac point shift of graphene phototransistors by doped silicon substrate current

Giant Dirac point shift of graphene phototransistors by doped silicon substrate current

Effects of substrate and anode metal annealing on InGaZnO Schottky diodes

Carrier density modulation in graphene underneath Ni electrode

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