Structural and electronic properties of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi mathvariant="normal">Ag</mml:mi><mml:mo>−</mml:mo><mml:mi mathvariant="normal">Pd</mml:mi></mml:mrow></mml:math>superlattices

Verstraete, Matthieu J.; Dumont, Jacques; Sporken, R.; Johnson, Robert L.; Wiame, Frédéric; Temst, Kristiaan; Swerts, Johan; Mirabella, F.; Ghijsen, J.; Gonze, Xavier

doi:10.1103/physrevb.70.205427

Cited by 9 publications

(2 citation statements)

References 33 publications

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“…The work function is the minimum energy required to extract an electron to a potential far from the surface. 30 The work function, WF is obtained from the following expression:…”

Section: B Theoretical Model and Methodsmentioning

confidence: 99%

Charge spill-out and work function of few-layer graphene on SiC(0 0 0 1)

Renault¹,

Pascon²,

Rotella³

et al. 2014

J. Phys. D: Appl. Phys.

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We report on the charge spill-out and work function of epitaxial few-layer graphene on 6H-SiC(0001). Experiments from high-resolution, energy-filtered X-ray photoelectron emission microscopy (XPEEM) are combined with ab initio Density Functional Theory calculations using a relaxed interface model. Work function values obtained from theory and experiments are in qualitative agreement, reproducing the previously observed trend of increasing work function with each additional graphene plane. Electrons transfer at the SiC/graphene interface through a buffer layer causes an interface dipole moment which is at the origin of the graphene work function modulation. The total charge transfer is independent of the number of graphene layers, and is consistent with the constant binding energy of the SiC component of the C 1s core-level measured by XPEEM. Charge leakage into vacuum depends on the number of graphene layers explaining why the experimental, layer-dependent C 1s-graphene core-level binding energy shift does not rigidly follow that of the work function. Thus, a combination of charge transfer at the SiC/graphene interface and charge spill-out into vacuum resolves the apparent discrepancy between the experimental work function and C1s binding energy. PACS 73.22.Pr, 71.15.Mb,

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“…The work function is the minimum energy required to extract an electron to a potential far from the surface. 30 The work function, WF is obtained from the following expression:…”

Section: B Theoretical Model and Methodsmentioning

confidence: 99%

Charge spill-out and work function of few-layer graphene on SiC(0 0 0 1)

Renault¹,

Pascon²,

Rotella³

et al. 2014

J. Phys. D: Appl. Phys.

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“…At this point the top surface of the column is constituted by a Pd core and a Ag brim and nucleation of Ag islands should occur on top of the Pd core in order to decrease the surface free energy. Nevertheless, as shown in a previous publication [42] the interface energy between a pseudomorphic Ag layer and Pd is around -90 meV per (111) surface unit cell. Therefore, in order to reduce both the surface and interface energy of the top layer, the incoming Ag atoms progressively exchange places with the top Pd core atoms until a full Ag layer is formed (Fig.…”

Section: Pd Growthmentioning

confidence: 94%

Demixing processes in AgPd superlattices

Dumont¹,

Sporken²,

Verstraete³

et al. 2009

J. Phys.: Condens. Matter

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Abstract. The present scanning tunneling microscopy (STM) study describes the growth of silver-palladium heterostructures at room temperature, with ab-initio simulations of ordered AgPd phases supporting the interpretation of STM images. First, the growth of Pd on a Ag(111) surface proceeds in a multilayer mode, leading to the formation of a columnar structure. Then, upon Ag deposition on this structure, Ag and Pd partially mix and form a two-dimensional AgPd alloy on top of the columns. Finally, an atomically flat Ag(111) surface is restored, and two-dimensional growth continues. An interpretation of this peculiar growth mode including interfacial alloying is proposed based on thermodynamic and kinetic arguments.

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Experimental and theoretical investigation of the superior contact properties of dielectrophoretically processed graphene and tantalum nitride electrodes

Pascon

Souza

Fonseca

et al. 2014

Physica Status Solidi (b)

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We have explored the dielectrophoretic process (DEP) to reach large scale integration of field effect transistors based on multilayer graphene (GraFET) deposited between source and drain metal electrodes. In our devices graphene lays on top of a TaO x gate dielectric deposited on an nþ silicon substrate, which is used as the back gate electrode, while the metal electrodes are made of TaN. These GraFETs reached a maximum transconductance of À19 mS/mm, which is higher than in silicon MOSFETs. To explain the origin of such good performance at the atomic level, ab initio calculations were conducted assuming two different models of the graphene/TaN interface: Ta-and N-terminated d-TaN[111] surfaces with one, two, three, and four layers of graphene on top. We have found that all graphene layers are considerably deformed due to strong interaction with both metal surfaces, and remain non-planar up to the fourth layer. We have also found that, except for the first graphene layer on TaN, all other layers display the Dirac cones in their locally projected density of states (PDOS). The reason for the absence of the Dirac cones in the first layer, an indication of poor conductance for monolayer graphene on TaN, is the metal induced surface states and not graphene deformation. Finally, due to the large work function of N-terminated TaN, the first few graphene layers closest to the interface are strongly p-doped, while for the Ta-terminated TaN which has low work function the first few graphene layers are slightly n-doped. The better adherence of graphene on N-terminated TaN and the strong p-doping of the interfacial graphene layers may explain the measured low contact resistance.

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Structural and electronic properties ofAg−Pdsuperlattices

Cited by 9 publications

References 33 publications

Charge spill-out and work function of few-layer graphene on SiC(0 0 0 1)

Charge spill-out and work function of few-layer graphene on SiC(0 0 0 1)

Demixing processes in AgPd superlattices

Experimental and theoretical investigation of the superior contact properties of dielectrophoretically processed graphene and tantalum nitride electrodes

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