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

Klein, Andreas

doi:10.1111/jace.12143

Cited by 134 publications

(93 citation statements)

References 167 publications

(387 reference statements)

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“…It was also shown that surface treatments such as plasma or chemical oxidation led to marked decrease in the separation between the main peak and the satellite for commercial ITO thin film samples with an Sn doping level of 8.8 % which in their native state showed a satellite energy of 0.85 eV, corresponding to a carrier density of 8.8 × 10 20 cm −3 . Very similar results were obtained by Gassenbauer et al for 9.2 % Sn doped In 2 O 3 thin films deposited in situ in the photoemission system [75,179,206] by magnetron sputtering in a pure Ar atmosphere [120]. Both In 3d 5/2 and O 1s core lines were fitted with single and double plasmon loss satellites with respective satellite energies of 0.89 and 1.10 eV [56].…”

Section: Satellite Structure In Core Level Photoemission Of Doped Samsupporting

confidence: 84%

Dopant and Defect Induced Electronic States at In2O3 Surfaces

Egdell

2015

Defects at Oxide Surfaces

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This article reviews the impact of defects and doping on the surface electronic structure of indium oxide, a wide gap oxide semiconductor which under degenerate doping becomes an important transparent conducting material. Topics covered include recent evidence for carrier accumulation at In 2 O 3 surfaces when there is a low bulk doping level and the profound effects of doping on core and valence photoemission spectra. The importance of molecular beam epitaxy in growth of single crystal samples is emphasised. IntroductionTransparent conducting oxides (TCOs) combine the usually orthogonal properties of optical transparency in the visible region with a high electrical conductivity [1][2][3][4]. TCOs already find widespread application as the window electrode in display devices including liquid crystal displays and electroluminescent display devices. A TCO electrode is also an essential component in many designs of solar cell [5,6]. In addition there is a growing interest in "transparent electronics" where TCO materials are employed in a more active role, for example in light emitting diodes [7] or lasers operating in the ultraviolet regime. The TCO market is worth around $1.6 billion per annum, with upward of 80 % of this sum based on LCD displays. Indium oxide (In 2 O 3 ) is amenable to n-type doping with Sn to give a prototype TCO usually-but somewhat misleadingly-referred to as indium tin oxide or ITO. At present ITO dominates the TCO market as the material offers a better combination of conductivity and transparency than alternatives such as doped ZnO or SnO 2 . In principle, doped CdO could achieve better performance [8], but Cd is highly toxic. Despite some recent reports of respiratory disease and even deaths [9] among workers in the ITO industry, indium is generally regarded as relatively

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Section: Satellite Structure In Core Level Photoemission Of Doped Samsupporting

confidence: 84%

Dopant and Defect Induced Electronic States at In2O3 Surfaces

Egdell

2015

Defects at Oxide Surfaces

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“…The films were produced within the Darmstadt Integrated System for Materials Research (DAISY-MAT) [13]. The DAISY-MAT consists of several deposition chambers connected via an ultra-high vacuum distribution chamber to a photoelectron spectroscopy (PES) analysis chamber, enabling in situ XPS analysis of the deposited films without breaking vacuum.…”

Section: Methodsmentioning

confidence: 99%

In Situ Hall Effect Monitoring of Vacuum Annealing of In2O3:H Thin Films

et al. 2015

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Hydrogen doped In2O3 thin films were prepared by room temperature sputter deposition with the addition of H2O to the sputter gas. By subsequent vacuum annealing, the films obtain high mobility up to 90 cm2/Vs. The films were analyzed in situ by X-ray photoelectron spectroscopy (XPS) and ex situ by X-ray diffraction (XRD), optical transmission and Hall effect measurements. Furthermore, we present results from in situ Hall effect measurements during vacuum annealing of In2O3:H films, revealing distinct dependence of carrier concentration and mobility with time at different annealing temperatures. We suggest hydrogen passivation of grain boundaries as the main reason for the high mobility obtained with In2O3:H films.

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“…37 This system permits thin film deposition by magnetron sputtering and characterization via monochromatic XPS (Physical Electronics PHI5700, Al K α , hν = 1486.6 eV) without breaking vacuum. Binding energies are recorded with respect to the Fermi energy, which is calibrated using a sputter-cleaned Ag foil.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Energy Band Alignment between Anatase and Rutile TiO₂

Pfeifer

Erhart

et al. 2013

J. Phys. Chem. Lett.

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227

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

Cited by 134 publications

References 167 publications

Dopant and Defect Induced Electronic States at In2O3 Surfaces

Dopant and Defect Induced Electronic States at In2O3 Surfaces

In Situ Hall Effect Monitoring of Vacuum Annealing of In2O3:H Thin Films

Energy Band Alignment between Anatase and Rutile TiO₂

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

Cited by 134 publications

References 167 publications

Dopant and Defect Induced Electronic States at In2O3 Surfaces

Dopant and Defect Induced Electronic States at In2O3 Surfaces

In Situ Hall Effect Monitoring of Vacuum Annealing of In2O3:H Thin Films

Energy Band Alignment between Anatase and Rutile TiO2

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Energy Band Alignment between Anatase and Rutile TiO₂