The Different Photoelectrochemical Behavior of Sintered and Flame‐Oxidized Fe2 O 3

Curran, J. S.; Gissler, W.

doi:10.1149/1.2128988

Cited by 55 publications

(24 citation statements)

References 4 publications

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“…5 and using interpolation, we estimate that the transition from "falling transient" to "rising transient" behavior occurs at about 0.25V for faces and at about 0.39V for edges. Curran and Gissler (1979) observed a similar transition between falling and rising transients, though at lower potentials than in this study.…”

Section: Resultssupporting

confidence: 79%

“…The rising transient is not observed for nanocrystalline hematite films but only for the natural single crystals. This is consistent with the Curran and Gissler (1979) interpretation. Charge transport must take place through several millimeters of hematite single crystal, but only through a few hundred nanometers of hematite for the films.…”

supporting

confidence: 92%

“…Because the rising transient becomes evident gradually with increasing E app , Curran and Gissler (1979) suggest that it is related to slow charge transport through hematite such that band bending takes place rather slowly as E app is increased. The rising transient is not observed for nanocrystalline hematite films but only for the natural single crystals.…”

mentioning

confidence: 99%

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Anisotropic photocatalytic properties of hematite

et al. 2009

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Hematite is a semiconducting mineral with a role in natural photoelectrochemical processes, and has been studied from the viewpoint of solar energy utilization. Hematite is an anisotropic conductor, with faster conduction parallel to (001) planes. Flatband potentials and photocurrent onset potentials for natural hematite single crystals and synthetic nanocrystalline hematite films are similar, and show Nernstian behavior within error. At pH 7, the flatband potential of single crystals is -0.25AE0.1 V vs. Ag/AgCl. Photocurrent onset potential is 0.02 to 0.03 V more negative for crystal faces than for crystal edges. Photocurrent density is a factor of 5 to 10 higher for crystal edges than for crystal (001) faces, presumably because of more rapid charge separation for the edges. Falling photocurrent transients decay more slowly for edges than for faces, consistent with more rapid removal of conduction band electrons into the bulk and therefore reduced availability of such electrons for back reaction. Rising photocurrent transients occur at higher potential, and have the same rise time for both faces and edges. This suggests that the rising transients are due to slow conduction through bulk hematite. The transition from falling to rising transients occurs at a more positive potential for edges than for faces, which is also consistent with more rapid charge transport away from edge surfaces and with Fermi level pinning at edges.

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Section: Resultssupporting

confidence: 79%

supporting

confidence: 92%

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Anisotropic photocatalytic properties of hematite

et al. 2009

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“…As already mentioned, similar behavior can be observed for TiO 2 and Fe 2 O 3 . [35][36][37][38] For these cases, the smaller cathodic transient might also be explained by assuming that a species ͑a surface-absorbed intermediate of the photo-oxidation of water͒ capable of capturing an electron from the conduction band is removed from the surface by a chemical reaction.…”

Section: Photocurrent Transient Behavior-the Transient Pc Measurementsmentioning

confidence: 99%

A Photoelectrochemical Study of In[sub x]Ga[sub 1−x]N Films

Theuwis

Strubbe

Depestel

et al. 2002

J. Electrochem. Soc.

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The III-nitride semiconductor n-In x Ga 1Ϫx N was investigated by optical absorbance and luminescence measurements and by various photoelectrochemical methods. Evidence is found for the presence of localized states and compositional fluctuations. Upon illumination with the appropriate wavelength and positive polarization in an indifferent electrolyte, i.e., aqueous 1 mol L Ϫ1 HCl, photocurrent flow is observed, resulting in the photoanodic etching of the solid. Measurements of the quantum efficiency Q and the transient photocurrent show that recombination of photogenerated charge carriers competes effectively with photoanodic dissolution.In the last decade, III-nitride materials such as GaN and In x Ga 1Ϫx N have been the subject of a considerable amount of research. Although the layers grown by metallorganic vapor-phase epitaxy ͑MOVPE͒ generally contain a large quantity of defects, highbrightness light-emitting diodes ͑LEDs͒ with excellent operating lifetimes as well as blue and violet laserdiodes, based upon these materials, are commercially available. 1,2 In the specific case of MOVPE-grown In x Ga 1Ϫx N layers, it has been demonstrated that indium is incorporated in the In x Ga 1Ϫx N lattice in an inhomogeneous way. 3-7 These fluctuations in composition may lead to substantial fluctuations in the bandgap energy E g of the alloy. Moreover, both extended and point defects are generally present in the alloy. 1,8 The aim of this study is to gain insight into the defect structure of this material. The use of ͑photo͒electrical characterization techniques such as photocurrent spectroscopy would require the formation of a high-quality rectifying semiconductor/metal contact. 9 However, to date little work has been done on the formation of good Schottky contacts on In x Ga 1Ϫx N. 10 In the present case, a semiconductor/electrolyte contact may constitute an elegant alternative to a semiconductor/metal contact for such studies.Despite the large amount of research done on III-N compoundbased optoelectronic devices, no suitable wet etchant has been found yet for In x Ga 1Ϫx N. 11 A photoelectrochemical study of the III-nitride/ electrolyte junction can also provide valuable information on the wet-etching behavior of this material. For GaN, such a study has already been conducted, both the photoanodic dissolution reaction and the open-circuit photoetching of GaN being investigated. 12 As in the case of In x Ga 1Ϫx N, no such study has to our knowledge been reported, so we have also performed this type of measurement in the present case. ExperimentalThe In x Ga 1Ϫx N films were grown by MOVPE at the Department of Information Technology at Ghent University. The In x Ga 1Ϫx N epi layers ͑x ϭ 0.21, to be discussed further, average thickness 1 m, unintentionally doped n-type͒ were grown on top of a structure consisting of a GaN epi layer, a 60 nm thick undoped GaN buffer layer, and a 350 m thick ͑0001͒ sapphire substrate.For details on the electrochemical measuring equipment and the electrode fabrication, see Ref. 12. Illuminati...

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“…[7] and [9]. Right at the start of the light pulses an immediate increase of photocurrent is expected.…”

Section: [9]mentioning

confidence: 99%