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1. Towards the first theoretical scale of the trans effect in octahedral complexes

Author

Christophe Morell, Frédéric Guégan, Laurent Joubert, Dominique Luneau, Henry Chermette, Vincent Tognetti, Laboratoire des Multimatériaux et Interfaces (LMI), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Chemometrics and Theoretical Chemistry - Chimiométrie et chimie théorique, Institut des Sciences Analytiques (ISA), Université de Lyon-Université de Lyon-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), Chimie Organique et Bioorganique : Réactivité et Analyse (COBRA), Institut Normand de Chimie Moléculaire Médicinale et Macromoléculaire (INC3M), Institut de Chimie du CNRS (INC)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Université Le Havre Normandie (ULH), Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie Organique Fine (IRCOF), Université de Rouen Normandie (UNIROUEN), and Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Ligand field theory, Trans effect, VALENCE, General Physics and Astronomy, 010402 general chemistry, 01 natural sciences, DENSITY-FUNCTIONAL THEORY, [CHIM.ANAL]Chemical Sciences/Analytical chemistry, Computational chemistry, 0103 physical sciences, CHEMICAL-REACTIVITY, Physical and Theoretical Chemistry, CISPLATIN BINDING, Valence (chemistry), CRYSTAL, 010304 chemical physics, Chemistry, Ligand, DUAL DESCRIPTOR, 0104 chemical sciences, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, Octahedron, METAL-COMPLEXES, LIGANDS, Density functional theory, BOND, NATURAL ORBITALS, [CHIM.CHEM]Chemical Sciences/Cheminformatics
Abstract

International audience; In this paper, we show that trans effects in octahedral complexes can primarily be related to differences in the ability, for a given ligand, to cede electron density to the metal cation under the influence of the ligand at the trans position. Using tools from conceptual DFT or from related paradigms, we highlight these effects on a set of representative examples and further provide the basis for a computational trans effect scale. This quantification notably retrieves the experimental trans orienting series.

Published
2016
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2. Atomic electronegativities in molecules

Author

Christophe Morell, Vincent Tognetti, Laurent Joubert, Chimie Organique et Bioorganique : Réactivité et Analyse (COBRA), Institut Normand de Chimie Moléculaire Médicinale et Macromoléculaire (INC3M), Institut de Chimie du CNRS (INC)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Université Le Havre Normandie (ULH), Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie Organique Fine (IRCOF), Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Chemometrics and Theoretical Chemistry - Chimiométrie et chimie théorique, Institut des Sciences Analytiques (ISA), Institut de Chimie du CNRS (INC)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), and V.T. and L.J. gratefully acknowledge the Centre National de la Recherche Scientifique (CNRS) for a 'Chaire d'Excellence' at the University of Rouen, the LABEX SynOrg for funding, and the CRIHAN computational centre for providing computational resources.

Subjects
NUCLEOPHILICITY, General Physics and Astronomy, chemistry.chemical_element, 010402 general chemistry, Kinetic energy, DFT, 01 natural sciences, DENSITY-FUNCTIONAL THEORY, Electronegativity, ELECTROPHILICITY, SYSTEMS, [CHIM.ANAL]Chemical Sciences/Analytical chemistry, Computational chemistry, 0103 physical sciences, CHEMICAL-REACTIVITY, Physics::Atomic and Molecular Clusters, Molecule, Reactivity (chemistry), Physics::Atomic Physics, Physics::Chemical Physics, Physical and Theoretical Chemistry, LOCAL IONIZATION ENERGIES, SCALE, Condensed Matter::Quantum Gases, 010304 chemical physics, Decomposition, 0104 chemical sciences, MODEL, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, chemistry, Chemical physics, Density functional theory, Carbon, KINETIC-ENERGY
Abstract

International audience; In this letter, we propose a straightforward evaluation of atomic electronegativities within the framework of Bader's atoms-in-molecules theory, based on the basin decomposition of the molecular electronic chemical potential derived from the Kohn-Sham equations through the non-interacting kinetic energy. The use of such atomic descriptors for reactivity purposes is then illustrated on the prediction of the electrophilicity of carbon atoms in organic reagents.

Published
2015
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3. Quantifying electro/nucleophilicity by partitioning the dual descriptor

Author

Vincent Tognetti, Christophe Morell, Laurent Joubert, Chimie Organique et Bioorganique : Réactivité et Analyse (COBRA), Institut Normand de Chimie Moléculaire Médicinale et Macromoléculaire (INC3M), Institut de Chimie du CNRS (INC)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Université Le Havre Normandie (ULH), Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie Organique Fine (IRCOF), Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Chemometrics and Theoretical Chemistry - Chimiométrie et chimie théorique, Institut des Sciences Analytiques (ISA), Institut de Chimie du CNRS (INC)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)

Subjects
INDEXES, halogen bonds, nucleophilicity, Context (language use), sigma-holes, 010402 general chemistry, 01 natural sciences, Measure (mathematics), ELECTROSTATIC POTENTIALS, DENSITY-FUNCTIONAL THEORY, INTERMOLECULAR INTERACTIONS, carbocations, conceptual DFT, [CHIM.ANAL]Chemical Sciences/Analytical chemistry, Quantum mechanics, CHEMICAL-REACTIVITY, SIGMA-HOLE, Molecule, Statistical physics, Quantum, 010405 organic chemistry, Chemistry, grid algorithm, General Chemistry, 0104 chemical sciences, Dual (category theory), CONDENSED FUKUI FUNCTION, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, Computational Mathematics, Density functional theory, atomic condensation, Constant (mathematics), electrophilicity, [CHIM.CHEM]Chemical Sciences/Cheminformatics, dual descriptor, Sign (mathematics)
Abstract

Translating local electro/nucleophilicities into the language of reactive sites is an appealing theoretical challenge that could be conducive to strengthen the collaborative dialogue between experimentalists and quantum chemists. The usual schemes for such condensation, relying on atomic charges, may however lead to important information loss, due to a sometimes inappropriate averaging of the reactivity anisotropy. In this article, we present instead an approach based on the dual descriptor Δf, which aims at partitioning real space into nonoverlapping reactive domains that feature a constant Δf sign. This strategy enables not only to identify the nucleo/electrophilic regions inside a molecule but also to quantify meaningful properties (mean value, volume, electron population…). Its interest is then illustrated on two specific chemical problems: the measure of σ-holes in the context of halogen bonds, and of the electrophilicity of organic carbocations, casting the light on the versatility of this method. © 2015 Wiley Periodicals, Inc.

Published
2015
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4. Dual descriptor and molecular electrostatic potential: complementary tools for the study of the coordination chemistry of ambiphilic ligands

Author

Vincent Tognetti, Laurent Joubert, Frédéric Guégan, Pierre Mignon, Christophe Morell, Institut des Sciences Analytiques (ISA), Institut de Chimie du CNRS (INC)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Chimie Organique et Bioorganique : Réactivité et Analyse (COBRA), Institut Normand de Chimie Moléculaire Médicinale et Macromoléculaire (INC3M), Institut de Chimie du CNRS (INC)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Université Le Havre Normandie (ULH), Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie Organique Fine (IRCOF), Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Normandie Université (NU), Chemometrics and Theoretical Chemistry - Chimiométrie et chimie théorique, Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université Claude Bernard Lyon 1 (UCBL), and The authors would like to thank Roald Hoffmann for his precious advice and discussions. F. G. is grateful to the Ecole Normale Superieure de Lyon for the financial support. This work has been partially supported by INSA Rouen, Rouen University, CNRS, Labex SynOrg (ANR-11-LABX-0029) and region Haute-Normandie (CRUNCh network). L. J. and V. T. thank the Centre National de la Recherche Scientifique (CNRS) for a 'chaire d'excellence' at the University of Rouen, and the Centre de Ressources Informatiques de Haute-Normandie (CRI-HAN) for computational resources. The research benefited from the support of Aviesan ITMO Cancer within the 'Cancer Plan 2009-2013' and the application of Action 3.3. A.

Subjects
Models, Molecular, Static Electricity, MODELS, General Physics and Astronomy, Electrons, Ligands, 010402 general chemistry, 01 natural sciences, DELTA-F(R), Coordination complex, DENSITY-FUNCTIONAL THEORY, chemistry.chemical_compound, CHARGE-TRANSFER, Coordination Complexes, [CHIM.ANAL]Chemical Sciences/Analytical chemistry, Computational chemistry, OXIDATIVE ADDITION, Organometallic Compounds, CHEMICAL-REACTIVITY, Molecule, Physical and Theoretical Chemistry, ComputingMilieux_MISCELLANEOUS, ORBITAL THEORY, Organometallic chemistry, chemistry.chemical_classification, RELEVANT, 010405 organic chemistry, Chemistry, Polyatomic ion, Diatomic molecule, Oxidative addition, STATE, 0104 chemical sciences, Dual (category theory), Quantum Theory, COMPLEXES, Density functional theory
Abstract

In this paper, we show that the ambiphilic properties of some organic ligands in organometallic complexes may be retrieved readily from simple calculations in the framework of conceptual density functional theory (C-DFT): namely, the dual descriptor (DD) and the molecular electrostatic potential (MEP) of the ligands afford a rather straightforward interpretation of experimental trends such as the bonding geometry and the electronic properties of complexes in terms of σ-, π- and back-bonding. The studied ligands were chosen to be representative of the wide variety organometallic chemistry offers, ranging from neutral to charged systems and from diatomic to polyatomic molecules. The present approach is general since all relevant parameters are retrieved from the electron density, obtained either from a DFT or post-Hartree-Fock calculation. It is believed to be helpful for organometallic chemists, since it allows a deep understanding and may be used as a predictive tool of the coordinating properties of ligands.

Published
2014
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5. Bond fukui indices: Comparison of frozen molecular orbital and finite differences through mulliken populations

Author

Andrés Cedillo, Patrick Bultinck, and Sofie Van Damme

Subjects
Density matrix, DUAL-DESCRIPTOR MATRICES, electronic-structure, Ab initio, PAIR DENSITY, Fukui function, Electronic structure, PARAMETERS, Mulliken, ENERGY, DENSITY-FUNCTIONAL THEORY, Computational chemistry, Ab initio quantum chemistry methods, Quantum mechanics, CHEMICAL-REACTIVITY, Molecular orbital, density functional theory, AB-INITIO, FRONTIER-ELECTRON THEORY, Chemistry, Atoms in molecules, General Chemistry, FRAMEWORK, WAVE FUNCTIONS, reactivity, Computational Mathematics, Models, Chemical, Quantum Theory, Density functional theory
Abstract

Bond Fukui functions and matrices are introduced for ab initio levels of theory using a Mulliken atoms in molecules model. It is shown how these indices may be obtained from first-order density matrix derivatives without need for going to second-order density matrices as in a previous work. The importance of taking into account the nonorthogonality of the basis in ab initio calculations is shown, contrasting the present results with previous work based on Huckel theory. It is shown how the extension of Fukui functions to Fukui matrices allows getting more insight into the nature of bond Fukui functions. All presently introduced indices respect the necessary normalization conditions and include the classical single atom condensed Fukui functions. © 2013 Wiley Periodicals, Inc.

Published
2013
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6. 3D QSAR based on conceptual DFT molecular fields: Antituberculotic activity

Author

Patrick Bultinck and Sofie Van Damme

Subjects
Quantitative structure–activity relationship, Field (physics), Biochemistry, DENSITY-FUNCTIONAL THEORY, SYSTEMS, Computational chemistry, Molecular property, CHEMICAL-REACTIVITY, Tuberculosis, 3D QSAR, Physical and Theoretical Chemistry, Quantum chemical, Drug discovery, Chemistry, Condensed Matter Physics, ANALYSIS COMFA, Physics and Astronomy, METABOLIZING CYP2A6 ENZYME, VIEWPOINT, Conceptual DFT, FUKUI FUNCTION, SHAPE, Density functional theory, PRINCIPLE, INHIBITORS, Fukui function
Abstract

We describe the use of conceptual DFT based quantum chemical molecular fields for three-dimensional quantitative structure–activity relations (3D QSARs) and compare this new approach with the use of the default molecular property fields. The use of the new molecular fields in 3D QSAR is investigated by an application in the field of drug discovery, in which the antituberculotic activity of salicylamide derivatives is investigated. It is shown that conceptual DFT molecular fields have an added value to the default considered CoMFA fields.

Published
2010
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7. Towards the rationalization of catalytic activity values by means of local hyper-softness on the catalytic site: a criticism about the use of net electric charges

Author

Jorge Ignacio Martínez-Araya, Daniel Glossman-Mitnik, André Grand, Universidad Andrés Bello [Santiago] (UNAB), Laboratoire Lésions des Acides Nucléiques (LAN), Service de Chimie Inorganique et Biologique (SCIB - UMR E3), Institut Nanosciences et Cryogénie (INAC), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Institut Nanosciences et Cryogénie (INAC), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), Universidad Andrés Bello - UNAB (CHILE), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Centre National de la Recherche Scientifique (CNRS)-Institut Nanosciences et Cryogénie (INAC), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS]Physics [physics], Steric effects, Substituent, General Physics and Astronomy, Polyethylene, Chemical-Reactivity, Fukui Functions, Correlation-Energy, Catalysis, chemistry.chemical_compound, Density-Functional Theory, Dual Descriptor, chemistry, Polymerization, Chemical engineering, Olefin Polymerization, Conceptual DFT, Computational chemistry, Pyridine, Electronic effect, Density functional theory, Physical and Theoretical Chemistry, Ethylene Polymerization, Effective Core Potentials
Abstract

International audience; By means of the Spin-Polarized Conceptual Density Functional Theory (SP-CDFT), three 2,6-bis(imino) pyridine catalysts based on iron(II), used for polymerization of ethylene, were studied. The catalysts differed by the substituent group, bearing either -H, -NO2 or -OCH3. To date, catalytic activity, a purely experimental parameter measuring the mass of polyethylene produced per millimole of iron per time and pressure unit at a fixed temperature, has not been explained in terms of local hyper-softness. The latter is a purely theoretical parameter designed for quantifying electronic effects; it is measured using the metal atom responsible for the coordination process with the monomer (ethylene). Because steric effects are not relevant in these kinds of catalysts and only electronic effects drive the catalytic process, an interesting link is found between catalytic activity and the local hyper-softness condensed on the iron atom by means of four functionals (B3LYP, BP86, B97D, and VSXC). This work demonstrates that the use of local hyper-softness, predicted by the SP-CDFT, is a suitable parameter for explaining order relationships among catalytic activity values, thus quantifying the electronic influence of the substituent group inducing this difference; the use of only net electric charges does not lead to clear conclusions. This finding can aid in estimating catalytic activities leading to a more rational design of new catalysts via computational chemistry.

Published
2015
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8. The Nature of the Micellar Stern Region As Studied by Reaction Kinetics. 2

Subjects
ESTER HYDROLYSIS, ASSOCIATION COLLOIDS, WATER-CATALYZED HYDROLYSIS, AQUEOUS-SOLUTIONS, ACID, technology, industry, and agriculture, CHEMICAL-REACTIVITY, INTERFACIAL COMPOSITIONS, lipids (amino acids, peptides, and proteins), NEUTRAL HYDROLYSIS, ARENEDIAZONIUM SALTS, POLARITY
Abstract

The nature of rate-retarding effects of cationic micelles on the water-catalyzed hydrolyses of a series of para-substituted 1-benzoyl-1,2,4-triazoles (1a-f) and 1-benzoyl-3-phenyl-1,2,4-triazole (2) has been studied using kinetic methods. A comparison is drawn between medium effects in the micellar Stern region and in model solutions for the micellar Stern region. Simple model solutions involving concentrated aqueous solutions of a small ionic molecule resembling the surfactant headgroup, as reported before,1 were improved. New model solutions for alkyltrimethylammonium bromide micelles contain both tetramethylammonium bromide (TMAB), mimicking micellar headgroups, and 1-propanol, mimicking hydrophobic tails. The rate-retarding effect of micelles on the hydrolysis of 1a-f and 2 is caused by the high concentration of headgroups as well as by hydrophobic tails in the Stern region where 1a-f and 2 bind to the micelle. Individual contributions of these interactions are quantified. Rate-retarding effects found for different probes, with different sensitivities for interactions as they occur when the probe binds to the micellar Stern region, as well as the micellar Stern region’s micropolarity as reported by the ET(30) probe, are satisfactorily reproduced by new model solutions containing both TMAB and 1-propanol.

Published
2004
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9. Internally detected electron photoexcitation spectroscopy on heterostructures

Author

Carlo Coluzza, Roberto Carluccio, A. Neglia, and G. Margaritondo

Subjects
SEMICONDUCTOR HETEROJUNCTIONS, Materials science, Band gap, Schottky barrier, Molecular physics, BAND, symbols.namesake, SCHOTTKY-BARRIER FORMATION, CHEMICAL-REACTIVITY, GE-GAAS(110) INTERFACES, SI, PHOTOEMISSION, HYDROGENATED AMORPHOUS-SILICON, Fermi level, Heterojunction, Surfaces and Interfaces, Condensed Matter Physics, Semimetal, Surfaces, Coatings and Films, INTERFACE, Band bending, STATES, GAP STATES, symbols, Direct and indirect band gaps, Atomic physics, Quasi Fermi level, DISCONTINUITIES
Abstract

We applied the internal photoemission technique to the direct observation of deep levels together with barrier heights and band discontinuities at different semiconductor heterostructure interfaces. Its performances and capabilities are superior to those of established techniques: the energy resolution is excellent and it can be applied to "real" device interfaces under bias. The technique was successfully tested for the Pd/n-GaAs and Pd/a-Si:H Schottky barriers as well as for the a-Ge/n-GaAs and a-Ge/p-GaP heterojunctions. We found a Pd/n-GaAs Schottky barrier height of 0.78 eV and an a-Ge/n-GaAs valence band discontinuity of 0.42 eV; in both cases the Fermi level was "pinned" at an averaged value of 0.76+/-0.03 eV above the top of the GaAs valence band. Furthermore we directly measured a feature at 1.09 eV, due to Pd-induced empty states approximately 1.1 eV above the valence band. The Pd/n-GaAs Schottky barrier also exhibits a feature at 1.36 eV, explained by transitions from the valence band to a localized state, made possible by the band bending. In the case of a-Ge/n-GaP we found a DELTA-E(V) = 0.88 +/- 0.05 eV and a DELTA-E(C) = 0.68 +/- 0.05 eV. Finally, in the Pd/a-Si:H Schottky barrier, we demonstrated the contribution of resonant tunneling through localized states of the conduction band.

Published
1992
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