Atomic Layer Deposition of Al2O3 onto Sn-Doped In2O3: Absence of Self-Limited Adsorption during Initial Growth by Oxygen Diffusion from the Substrate and Band Offset Modification by Fermi Level Pinning in Al2O3

Bayer, Thorsten J. M.; Wachau, André; Fuchs, Anne; Deuermeier, Jonas; Klein, Andreas

doi:10.1021/cm301732t

Cited by 37 publications

(71 citation statements)

References 71 publications

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“…Transitivity of energy band alignment has been demonstrated explicitly using two different conducting oxides as contact materials, which gives confidence that the experimentally determined alignment is not corrupted by defect-induced Fermi level pinning. 22,39 The obtained band alignments support previous studies by Deaḱ et al 15 and Scanlon et al 16 Moreover, the analysis of the electronic structure shows that the higher valence band maximum of rutile is caused by the stronger overlap between the O 2p z orbitals in rutile compared to those in anatase, leading to a substantial splitting of the resulting energy bands. The staggered band alignment explains the enhanced photocatalytic activity of mixed phase TiO 2 particles 4−9 as it provides a driving force for separation of photoexcited charge carriers.…”

supporting

confidence: 87%

Energy Band Alignment between Anatase and Rutile TiO₂

Pfeifer

Erhart

et al. 2013

J. Phys. Chem. Lett.

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Using photoelectron spectroscopy, the interface formation of anatase and rutile TiO 2 with RuO 2 and tin-doped indium oxide (ITO) is studied. It is consistently found that the valence band maximum of rutile is 0.7 ± 0.1 eV above that of anatase. The alignment is confirmed by electronic structure calculations, which further show that the alignment is related to the splitting of the energy bands formed by the O 2p z lone-pair orbitals. The alignment can explain the different electron concentrations in doped anatase and rutile and the enhanced photocatalytic activity of mixed phase particles.SECTION: Surfaces, Interfaces, Porous Materials, and Catalysis A fter Fujishima and Honda 1 had reported on the photocatalytic activity of TiO 2 , the influence of crystal structure on this property was investigated intensively.2,3 Over the past 2 decades, it was commonly observed that mixed anatase/rutile systems show more favorable photocatalytic properties than pristine ones of either modification. 4−9 The synergistic effect of the mixed systems has been attributed to a built-in driving force for separation of photogenerated charge carriers. Such a driving force may result from either a built-in electric field or from energy barriers blocking charge transfer at the interface between anatase and rutile. The latter are described by the energy band alignment, which is well-studied for semiconductor interfaces. Connelly et al.11 recently reviewed several models that are trying to explain the synergistic effect of mixed anatase/rutile systems. Well-known are the rutile sink model of Bickley et al. 4 and the rutile antenna model of Hurum et al., 5 which place the band edges of rutile (energy band gap E g = 3.0 eV 12 ) in between the band edges of anatase (E g = 3.2 eV 13 ). Kavan et al.14 performed electrochemical measurements that located the conduction band edge of anatase 0.2 eV above that of rutile, which corresponds to aligned valence band maxima. These models, however, were not able to convincingly account for the observed synergistic phenomena. Only recently, Deaḱ et al. 15 as well as Scanlon et al. 16 found theoretical and experimental indications for an energy band alignment with valence and conduction band energies in rutile both located higher in energy than in anatase when brought into contact. With such a staggered energy band alignment at the anatase/rutile interface, photogenerated electrons will preferentially move to anatase due to its lower conduction band minimum energy E CB , and holes will move to rutile due to its higher valence band maximum energy E VB . Deaḱ et al. 15 used the alignment of branch point energies 10 for their calculations. For oxides, though, it has been shown that due to a low density of induced interface states, the alignment of branch point energies does not necessarily yield proper results for the energy band alignment. 17In this work, further evidence for a staggered energy band alignment at the anatase/rutile interface is provided by X-ray photoelectron spectroscopy (XPS)...

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supporting

confidence: 87%

Energy Band Alignment between Anatase and Rutile TiO₂

Pfeifer

Erhart

et al. 2013

J. Phys. Chem. Lett.

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227

155

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“…. Several examples for such a behavior with a variation in band alignment of up to 1 eV have been discussed in literature including ZnO/CdS, ITO/Al 2 O 3 , ITO/Cu 2 O, ZnO/In 2 S 3 , and In 2 O 3 /CdS interfaces.…”

Section: Energy Band Alignmentmentioning

confidence: 99%

“…Chemical bath deposited CdS films, e.g., can also exhibit lower Fermi level positions. Whereas the nature of the defects responsible for the pinning in evaporated CdS films is not yet clear, pinning observed in atomic layer deposited Al 2 O 3 films has been suggested to be caused by the incorporation of hydrogen during the growth process …”

Section: Energy Band Alignmentmentioning

confidence: 99%

Transparent Conducting Oxides: Electronic Structure–Property Relationship from Photoelectron Spectroscopy with in situ Sample Preparation

Klein

2012

J. Am. Ceram. Soc.

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134

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The various applications of transparent conducting oxides (TCO), e.g., as electrodes in flat panel displays and solar cells or as low‐emissivity coatings have stimulated extensive research on their fabrication and properties. Recent experimental and theoretical studies of defect properties have considerably improved the understanding of the limitations of the electrical conductivity of both n‐ and p‐type transparent conductors and of the structural and electronic surface properties of the most important TCO materials. Development of emerging and future applications in the area of transparent thin film electronics with oxide semiconductors as well as the improvement of existing applications require a detailed control of the Fermi level position in the bulk and at surfaces and interfaces of polycrystalline and amorphous TCO materials. This feature article describes how the important parameters for such control can be identified using photoelectron spectroscopy with in situ sample preparation. The parameters influencing doping, work functions, ionization potentials, and surface band bending as well as energy band alignment at interfaces are described and discussed providing a fundamental understanding of important material properties for tailoring TCOs in electronic devices.

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“…Significant variation of band alignment by up to ∼1 eV depending on sample preparation has been reported for interfaces between CdS or In 2 S 3 and different oxide materials , as well as for interfaces of ITO with Cu 2 O and with Al 2 O 3 . In all these cases, the modification of the band alignment can be attributed to the limitation of band bending in the corresponding materials .…”

Section: Resultsmentioning

confidence: 98%

“…In all these cases, the modification of the band alignment can be attributed to the limitation of band bending in the corresponding materials . Such a limitation can be caused by charged crystallographic defects if the evolution of a band bending causes a change of the charge state of the defects . Such contributions may also explain the different valence band offsets observed at the CuInS 2 /CdS interface.…”

Section: Resultsmentioning

confidence: 99%

Valence band offsets at Cu(In,Ga)Se₂/Zn(O,S) interfaces

Adler

Botros

Witte

et al. 2013

Phys. Status Solidi A

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The energy band alignment at interfaces between Cuchalcopyrites and Zn(O,S) buffer layers, which are important for thin-film solar cells, are considered. Valence band offsets derived from X-ray photoelectron spectroscopy for Cu(In,Ga) Se 2 absorber layers with CdS and Zn(O,S) compounds are compared to theoretical predictions. It is shown that the valence band offsets at Cu(In,Ga)Se 2 /Zn(O,S) interfaces approximately follow the theoretical prediction and vary significantly from sample to sample. The integral sulfide content of chemical bath deposited Zn(O,S) is reproducibly found to be 50-70%, fortuitously resulting in a conduction band offset suitable for solar cell applications with Cu(In,Ga)Se 2 absorber materials. The observed variation in offset can neither be explained by variation of the Cu content in the Cu(In,Ga)Se 2 near the interface nor by local variation of the chemical composition. Fermi level pinning induced by high defect concentrations is a possible origin of the variation of band offset.

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Atomic Layer Deposition of Al₂O₃ onto Sn-Doped In₂O₃: Absence of Self-Limited Adsorption during Initial Growth by Oxygen Diffusion from the Substrate and Band Offset Modification by Fermi Level Pinning in Al₂O₃

Cited by 37 publications

References 71 publications

Energy Band Alignment between Anatase and Rutile TiO₂

Energy Band Alignment between Anatase and Rutile TiO₂

Transparent Conducting Oxides: Electronic Structure–Property Relationship from Photoelectron Spectroscopy with in situ Sample Preparation

Valence band offsets at Cu(In,Ga)Se₂/Zn(O,S) interfaces

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Atomic Layer Deposition of Al2O3 onto Sn-Doped In2O3: Absence of Self-Limited Adsorption during Initial Growth by Oxygen Diffusion from the Substrate and Band Offset Modification by Fermi Level Pinning in Al2O3

Cited by 37 publications

References 71 publications

Energy Band Alignment between Anatase and Rutile TiO2

Energy Band Alignment between Anatase and Rutile TiO2

Transparent Conducting Oxides: Electronic Structure–Property Relationship from Photoelectron Spectroscopy with in situ Sample Preparation

Valence band offsets at Cu(In,Ga)Se2/Zn(O,S) interfaces

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About

Atomic Layer Deposition of Al₂O₃ onto Sn-Doped In₂O₃: Absence of Self-Limited Adsorption during Initial Growth by Oxygen Diffusion from the Substrate and Band Offset Modification by Fermi Level Pinning in Al₂O₃

Energy Band Alignment between Anatase and Rutile TiO₂

Energy Band Alignment between Anatase and Rutile TiO₂

Valence band offsets at Cu(In,Ga)Se₂/Zn(O,S) interfaces