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Alfredo Pasquarello

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Related publications (226)

Origin of Fermi-level pinning at GaAs surfaces and interfaces

Alfredo Pasquarello, Davide Colleoni, Giacomo Francesco Leonardo Miceli

Through first-principles simulation methods, we assign the origin of Fermi-level pinning at GaAs surfaces and interfaces to the bistability between the As-As dimer and two As dangling bonds, which transform into each other upon charge trapping. This defect ...

Institute of Physics2014

Band offsets of lattice-matched semiconductor heterojunctions through hybrid functionals and G(0)W(0)

Alfredo Pasquarello, Karim Steiner, Wei Chen

To assess the accuracy of hybrid functional and many-body GW methods, we study the band offsets for a set of lattice-matched semiconductor heterojunctions, including AlAs/GaAs(100), AlP/GaP(100), Si/GaP(110), Ge/GaAs(110), Ge/AlAs(110), Ge/ZnSe(110), and Z ...

2014

The O-As defect in GaAs: A hybrid density functional study

Alfredo Pasquarello, Davide Colleoni

The O center substitutional to As (O-As) is addressed through hybrid functional calculations as a candidate defect to explain the Fermi-level pinning in oxygen-doped GaAs. The defect center shows amphoteric behavior which could lead to Fermi-level pinning. ...

Elsevier2014

Defect levels at GaAs/Al2O3 interfaces: As-As dimer vs. Ga dangling bond

Alfredo Pasquarello, Giacomo Francesco Leonardo Miceli

Charge transition levels of the As-As dimer and the Ga dangling bond at GaAs/Al2O3 interfaces are determined through density-functional calculations. The same parent interface model structure is used as a starting point for creating both defects providing ...

Elsevier2014

Intercalation of H at the graphene/SiC(0001) interface: Structure and stability from first principles

Alfredo Pasquarello, Gabriele Sclauzero

We investigate the intercalation of hydrogen at the graphene/SiC(0001) interface through atomistic models characterized by very low strains both in the epitaxial graphene and in the SiC substrate. Adsorption of H at the interface is always stable but shows ...

Elsevier2014

Infrared spectra of jennite and tobermorite from first-principles

Alfredo Pasquarello, Alexandre Vidmer, Gabriele Sclauzero

The infrared absorption spectra of jennite, tobermorite 14 angstrom, anomalous tobermorite 11 angstrom, and normal tobermorite 11 angstrom are simulated within a density-functional-theory scheme. The atomic coordinates and the cell parameters are optimized ...

Pergamon-Elsevier Science Ltd2014

Assignment of Fermi-level pinning and optical transitions to the (As-Ga)(2)-O-As center in oxygen-doped GaAs

Alfredo Pasquarello, Davide Colleoni

The (As-Ga)(2)-O-As defect in oxygen-doped GaAs, consisting of two As antisites neighboring an O center substitutional to As, is addressed through hybrid functional calculations. This defect not only accounts for the nearest neighbor environment of the O a ...

2013

First-principles study of H adsorption on graphene/SiC(0001)

Alfredo Pasquarello, Gabriele Sclauzero

The adsorption of atomic H above the carbon buffer layer in the graphene/SiC(0001) interface system is investigated within density functional theory through a set of realistic interface models that do not impose large artificial strains on the graphene. We ...

Wiley-Blackwell2013

Accurate determination of charge transition levels of the As-As dimer defect at GaAs/oxide interfaces through hybrid functionals

Alfredo Pasquarello, Giacomo Francesco Leonardo Miceli

The energy levels of the As-As dimer defect at GaAs/oxide interfaces are accurately determined within a hybrid functional scheme and aligned with respect to the GaAs band gap. An As-As dimer is constructed at a model interface between GaAs and kappa-Al2O3, ...

2013

First principles study of As 2p core-level shifts at GaAs/Al2O3 interfaces

Alfredo Pasquarello, Giacomo Francesco Leonardo Miceli

Arsenic 2p core-level shifts at GaAs/Al2O3 interfaces are determined with respect to bulk GaAs through density functional calculations. Atomistic interface models are constructed in which As atoms are found in various chemical environments. Both Ga-termina ...

American Institute of Physics2013

Amphoteric defects in GaAs leading to Fermi-level pinning: A hybrid functional study

Alfredo Pasquarello, Davide Colleoni

Formation energies and charge transition levels of amphoteric defects in GaAs giving rise to Fermi-level pinning are calculated with hybrid functionals. The hybrid functional results indicate that previously identified defects involving the bistable nature ...

Elsevier2013

Finite-Size Supercell Correction for Charged Defects at Surfaces and Interfaces

Alfredo Pasquarello, Hannu-Pekka Komsa

A finite-size supercell correction scheme is introduced for the formation energy of charged defects at surfaces and interfaces. The scheme combines classical electrostatics with the dielectric profile and the electrostatic potential extracted from the elec ...

American Physical Society2013

Correspondence of defect energy levels in hybrid density functional theory and many-body perturbation theory

Alfredo Pasquarello, Wei Chen

We demonstrate the correspondence between charge transition levels of localized point defects in hybrid density functional theory and in G(0)W(0) many-body perturbation theory. To achieve this correspondence, it is necessary to properly combine the treatme ...

2013

Defect energy levels of the As-As dimer at InGaAs/oxide interfaces: A first principles study

Alfredo Pasquarello, Giacomo Francesco Leonardo Miceli

Charge transition levels of the As-As dimer defect at the InGaAs/Al2O3 interface are determined through density-functional calculations. At variance with the GaAs/Al2O3 interface where this defect gives rise to states within the band gap, its defect levels ...

Elsevier2013

Band-edge levels in semiconductors and insulators: Hybrid density functional theory versus many-body perturbation theory

Alfredo Pasquarello, Wei Chen

We compare band-edge levels as obtained with hybrid functionals and GW perturbation theory for a wide class of materials. For sp-bonded semiconductors, a close agreement is demonstrated. However, deviations for other materials are more significant and rang ...

2012

Finite-size supercell correction schemes for charged defect calculations

Alfredo Pasquarello, Hannu-Pekka Komsa

Various schemes for correcting the finite-size supercell errors in the case of charged defect calculations are analyzed and their performance for a series of defect systems is compared. We focus on the schemes proposed by Makov and Payne (MP), Freysoldt, N ...

2012

Medium range structure of tetrahedrally-bonded glasses through the first principles investigation of Raman spectra

Alfredo Pasquarello, Luigi Giacomazzi

We calculate the Raman spectra of vitreous SiO 2 , vitreous GeO 2 , and vitreous GeSe 2 within a density functional scheme. Due to the sensitivity of the Raman spectra to correlations extending beyond the tetrahedral unit, we extract through the comparison ...

2012

Low-strain interface models for epitaxial graphene on SiC(0001)

Alfredo Pasquarello, Gabriele Sclauzero

A set of low-strain commensurate interface structures for epitaxial graphene on SiC(0001) are obtained by combining rotated graphene supercells with m x m or m root 3 x m root 3R30 degrees SiC cells. For two among the interfaces with lowest strain, corresp ...

Elsevier2012

Carbon rehybridization at the graphene/SiC(0001) interface: Effect on stability and atomic-scale corrugation

Alfredo Pasquarello, Gabriele Sclauzero

We address the energetic stability of the graphene/SiC(0001) interface and the associated binding mechanism by studying a series of low-strain commensurate interface structures within a density functional scheme. Among the structures with negligible strain ...

2012

Germanium core-level shifts at Ge/GeO2 interfaces through hybrid functionals

Alfredo Pasquarello, Peter Broqvist, Jan Felix Binder, Hannu-Pekka Komsa

The Ge core-level shift across the Ge/GeO2 interface is determined within semilocal and hybrid density functional schemes. We first assess the accuracy achieved within these theoretical frameworks by comparing calculated and measured core-level shifts for ...

2012

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