“…There is a substantial discrepancy between the local WF values measured along the surface for small surface areas, 47,48 which is related to surface lateral heterogeneity. While such effects are interesting, the WF data of polycrystalline materials are more representative when measured for larger surface areas.…”
This
work provides a summary of progress in emerging areas of the
science of materials interfaces and interface engineering of energy
materials. The progress, which is focused on gas–solid reactivity
of oxide materials, indicates that the high-temperature electron probe
(HTEP) offers new insight into the local-defect-related properties
of the surface layer that are critical for understanding the reactivity
of solids and the related charge transfer. The probe enables unequivocal
surface characterization of energy materials in gas–solid equilibrium
and in situ surface monitoring during processing
and performance at elevated temperatures. Specific progress has been
achieved in understanding the impact of both chemisorption and surface
segregation on the formation of quasi-isolated surface structures
(QISSs) that play a crucial role in gas–solid reactivity. The
key feature of the HTEP is the ability to measure work function (WF),
which is the defect-related surface property, while the surface layer
is in thermodynamic equilibrium with the gas phase on one side and
the bulk phase on the other. The summary indicates that the progress
in energy materials requires recognition that surface properties are
determined by structural defects within the surface layer. The probe,
which has a wide range of applications in materials engineering, ceramics,
catalysis, chemical engineering, metallurgy, nuclear fusion, and high-temperature
materials, opens up new areas of the science of materials interfaces
and interface engineering. The latter is of critical importance in
the development of materials for environmentally friendly energy conversion.
“…There is a substantial discrepancy between the local WF values measured along the surface for small surface areas, 47,48 which is related to surface lateral heterogeneity. While such effects are interesting, the WF data of polycrystalline materials are more representative when measured for larger surface areas.…”
This
work provides a summary of progress in emerging areas of the
science of materials interfaces and interface engineering of energy
materials. The progress, which is focused on gas–solid reactivity
of oxide materials, indicates that the high-temperature electron probe
(HTEP) offers new insight into the local-defect-related properties
of the surface layer that are critical for understanding the reactivity
of solids and the related charge transfer. The probe enables unequivocal
surface characterization of energy materials in gas–solid equilibrium
and in situ surface monitoring during processing
and performance at elevated temperatures. Specific progress has been
achieved in understanding the impact of both chemisorption and surface
segregation on the formation of quasi-isolated surface structures
(QISSs) that play a crucial role in gas–solid reactivity. The
key feature of the HTEP is the ability to measure work function (WF),
which is the defect-related surface property, while the surface layer
is in thermodynamic equilibrium with the gas phase on one side and
the bulk phase on the other. The summary indicates that the progress
in energy materials requires recognition that surface properties are
determined by structural defects within the surface layer. The probe,
which has a wide range of applications in materials engineering, ceramics,
catalysis, chemical engineering, metallurgy, nuclear fusion, and high-temperature
materials, opens up new areas of the science of materials interfaces
and interface engineering. The latter is of critical importance in
the development of materials for environmentally friendly energy conversion.
“…Ismail et al have shown that WF is a local property of a specific surface site, which may change along the surface. Figure represents the image of the WF for InP showing that WF exhibits changes by ∼0.5 eV within a 1 mm distance.…”
Section: Photoelectrochemical Properties Of the Pt−tio2
Systemmentioning
confidence: 99%
“…These data indicate that the charge transfers within a photocatalytic system should satisfy the charge neutrality condition, which requires that cathodic and anodic currents must be identical. 36 Work function map for the surface of InP showing the areas of different work function values according to Ismail et al 37 Model of a micro-photoelectrochemical cell involving both cathodic and anodic sites: (a) TiO 2 -based cell involving Pt active sites (organic water solutes are represented by CH 3 OH), (b) general model representing the surface charge required for charge separation and the related charge transfer. …”
Section: Photoelectrochemical Properties Of the Pt−tio2
Systemmentioning
confidence: 99%
“…Work function map for the surface of InP showing the areas of different work function values according to Ismail et al …”
Section: Photoelectrochemical Properties Of the Pt−tio2
Systemmentioning
The present work brings together the concepts of defect chemistry and photoelectrochemistry in order to
consider TiO2-based photosensitive oxide semiconductors as photocatalysts for water purification. This paper
reports the most recent progress in the defect chemistry of TiO2 and its solid solutions with aliovalent ions
forming donors and acceptors. The relationship between the defect-related properties, such as electrical and
photocatalytic properties, are outlined. It is shown that reactivity, photoreactivity, and the related charge
transfer of photocatalysts based on TiO2 are determined by defect disorder and the related chemical potential
of electrons. Therefore, defect chemistry may be used as a framework for the processing of well-defined
TiO2-based photocatalysts. The photoreactivity of TiO2 with water and its solutes is considered in terms of
the effect of both collective and local properties. The effect of noble metals attached to TiO2 as a separate
phase, such as platinum, on photoelectrochemical properties and the related photocatalytic performance of
TiO2 is discussed. The key functional properties, which are responsible for the efficient conversion of solar
energy into chemical energy (required for water purification), are outlined. The effect of TiO2 doping with
aliovalent ions on properties is considered in terms of the doping mechanisms and the related semiconducting
properties. It is argued that comparison of the experimental data reported in the literature on the photocatalytic
properties of TiO2 dictates the need to establish standards for photocatalysts, which are well-defined. This
paper reports the processing conditions of well-defined TiO2. It is argued that knowledge of the mass transport
kinetic data, such as chemical and self-diffusion coefficients, is needed for selecting the optimal processing
conditions.
“…Appl. 24 (1989) [45][46][47][48][49][50] décennies, a permis une avancée importante dans la compréhension de l'interaction métal-semiconducteur, en particulier dans le cas des composés III-V. Ces matériaux, outre leur intérêt technologique lié à la largeur de leur bande interdite ou à leur mobilité, peuvent présenter une surface exempte d'état électronique dans la bande interdite : c'est la surface (110) obtenue par clivage [3][4][5]. Il a ainsi été démontré que l'interaction de ces surfaces avec un métal (ainsi d'ailleurs qu'avec des atomes non métalliques) produit, dès les premiers stades du dépôt, un ancrage du niveau de Fermi qui explique en grande partie la valeur de la barrière 4>B mesurée dans les diodes Schottky [6][7][8][9].…”
To cite this version: M. Benkacem, M. Dumas, J.-M. Palau, L. Lassabatère. Etude de diodes Schottky réalisées sous ultravide par dépôt d'aluminium ou d'argent sur GaP type N clivé. Résumé. 2014 On présente les résultats de la caractérisation I(V) en direct et 1/C2(V) en inverse de diodes Schottky Al/GaP et Ag/GaP réalisées sous ultra-vide sur la face (110) clivée d'un barreau de type n. Deux types de surfaces ont été utilisées : les surfaces vierges et les surfaces recuites à 650 K pendant une heure. Ces surfaces ont préalablement été étudiées à la sonde de Kelvin et par spectroscopie Auger [1, 2]. Les diodes ont une barrière I(V) comprise entre 1,1 et 1,2 eV. Les caractéristiques 1/C2(V) sont linéaires mais conduisent à des hauteurs de barrière très sensiblement supérieures. De façon générale, le recuit préalable de la surface conduit à des diodes de moins bonne qualité : barrière légèrement diminuée, accroissement du facteur d'idéalité, non-linéarité à bas niveau de courant. Nous proposons une explication basée sur la présence d'états d'interface enfouis, déterminant la hauteur et la forme de la barrière et pouvant participer au transport du courant.Abstract. 2014 Forward I(V) and reverse 1/C2(V) results obtained for Al/GaP and Ag/GaP Schottky diodes 2. Conditions expérimentales.
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