Measurement of semiconductor heterojunction band discontinuities by x-ray photoemission spectroscopy

Waldrop, J. R.; Grant, R. W.; Kowalczyk, S. P.; Kraut, E. A.

doi:10.1116/1.573326

Cited by 136 publications

(80 citation statements)

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“…These are derived from the core level binding energies by subtracting the binding energy difference of the PZT core levels with respect to the PZT valence band maximum of the uncovered substrates. The core level to valence band maximum binding energy difference is constant for a material and should not change during metal deposition if no strong chemical disruption of the substrate occurs [43,44,45]. The PZTrelated core level emissions, including the oxidic Pb +II 4f component, exhibit parallel shifts during metal deposition for all three interfaces as evident from Figure 3(a-c).…”

Section: Resultsmentioning

confidence: 71%

Reduction-induced Fermi level pinning at the interfaces between Pb(Zr,Ti)O₃ and Pt, Cu and Ag metal electrodes

Chen¹,

Schafranek²,

Wu³

et al. 2011

J. Phys. D: Appl. Phys.

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Abstract.The interface formation between Pb(Zr,Ti)O 3 and Pt, Cu and Ag was studied using in situ photoelectron spectroscopy. A strong interface reaction and a reduction of the substrate surface is observed for all three interfaces as evidenced by the appearance of metallic Pb species. Despite the different work function of the metals, nearly identical barrier heights are found with E F − E VB = 1.6 ± 0.1 eV, 1.8 ± 0.1 eV and 1.7 ± 0.1 eV of the as-prepared interfaces with Pt, Cu and Ag, respectively. The barrier heights are characterized by a strong Fermi level pinning, which is attributed to an oxygen deficient interface induced by the chemical reduction of Pb(Zr,Ti)O 3 during metal deposition.

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Section: Resultsmentioning

confidence: 71%

Reduction-induced Fermi level pinning at the interfaces between Pb(Zr,Ti)O₃ and Pt, Cu and Ag metal electrodes

Chen¹,

Schafranek²,

Wu³

et al. 2011

J. Phys. D: Appl. Phys.

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“…The vast majority of the heterovalent interfaces presently studied tends to relax with a slight expansion in the overall length, with shifts in individual positions specific to the atomic species at the interface. The VBOs of the relaxed heterovalent interfaces are summarized in Table 2 and compared with experimental results, [54][55][56][57][58][59][60][61][62][63][64][65][66] where available. Results calculated for several heterojunctions between lattice-matched II-VI and group IV semiconductors are also included in Table 2 and can be seen to approximately display the same systematic trend as observed for III-V/IV and II-VI/III-V heterojunctions.…”

Section: Charge Transfer Considerations At Relaxed "Neutral" Interfacesmentioning

confidence: 99%

Charge Density and Band Offsets at Heterovalent Semiconductor Interfaces

Tung

Kronik

2017

Advcd Theory and Sims

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The well-known insensitivity of the band offset (BO) of isovalent heterojunctions with the zincblende structure to the orientation, abruptness, and atomic structure of the interface was recently shown to be attributable to a localness in the dependence of charge density on the atomic structure. In contrast, a sharp dependence of the BO on interface specifics has been observed at heterovalent heterojunctions. Here, detailed analyses of the relationship between the BO, interface structure, and charge distribution have been carried out for many lattice-matched heterovalent interfaces between zincblende and diamond structure semiconductors. From thermodynamic considerations, three types of neutral interfaces were investigated, each with equal densities of donor-and acceptor-like heterovalent bonds, constructible in all orientations. Distinctively different, yet approximately orientation-independent, valence BOs were found. The equilibrium charge density of the heterovalent interface could be recreated with the charge densities of bulk semiconductors and oligo-cells. Because charge transfer between heterovalent bonds is identifiable with that for dopants in semiconductor and its effect accountable by linear response, a combination of neutral polyhedra theory, previously developed for isovalent heterojunctions, and dielectric screening theory was found to explain BO trends throughout, allowing a strategy that facilitates adjustment in the BO of all isovalent heterojunctions.

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“…23 The binding energy differences ΔE CL,VB , which are material constants, are used below to derive the energy band alignment from the interface experiments using the Kraut method. 18 The large disparity of binding energy differences has been observed not only for the polycrystalline anatase and single-crystalline rutile samples but also for a number of other samples of the two modifications in poly-and single-crystalline structure (see Figure S2 in the Supporting Information). The ΔE CL,VB are in good agreement with our electronic structure calculations (see Figure 3 and the Supporting Information).…”

mentioning

confidence: 95%

Energy Band Alignment between Anatase and Rutile TiO₂

Pfeifer

Erhart

et al. 2013

J. Phys. Chem. Lett.

227

155

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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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Measurement of semiconductor heterojunction band discontinuities by x-ray photoemission spectroscopy

Cited by 136 publications

References 0 publications

Reduction-induced Fermi level pinning at the interfaces between Pb(Zr,Ti)O₃ and Pt, Cu and Ag metal electrodes

Reduction-induced Fermi level pinning at the interfaces between Pb(Zr,Ti)O₃ and Pt, Cu and Ag metal electrodes

Charge Density and Band Offsets at Heterovalent Semiconductor Interfaces

Energy Band Alignment between Anatase and Rutile TiO₂

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Measurement of semiconductor heterojunction band discontinuities by x-ray photoemission spectroscopy

Cited by 136 publications

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Reduction-induced Fermi level pinning at the interfaces between Pb(Zr,Ti)O3 and Pt, Cu and Ag metal electrodes

Reduction-induced Fermi level pinning at the interfaces between Pb(Zr,Ti)O3 and Pt, Cu and Ag metal electrodes

Charge Density and Band Offsets at Heterovalent Semiconductor Interfaces

Energy Band Alignment between Anatase and Rutile TiO2

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Reduction-induced Fermi level pinning at the interfaces between Pb(Zr,Ti)O₃ and Pt, Cu and Ag metal electrodes

Reduction-induced Fermi level pinning at the interfaces between Pb(Zr,Ti)O₃ and Pt, Cu and Ag metal electrodes

Energy Band Alignment between Anatase and Rutile TiO₂