Chemisorption of H2O on GaN(0001)

Bermudez, V. M.; Long, J. P.

doi:10.1016/s0039-6028(00)00051-0

Cited by 73 publications

(90 citation statements)

References 34 publications

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“…Its location with respect to the valence band maximum is identical to the state reported by Bermudez [8] on GaN after exposure to molecular oxygen. This is an indication that the oxidation by molecular water and molecular oxygen results in a similar surface structure as already discussed in [2]. Since component C can only be detected for higher exposures, it is possibly related to a chemisorption site which involves further breaking of GaN surface bonds.…”

Section: Contributedsupporting

confidence: 70%

“…As a consequence the signals from the underlying Ga an N atoms are attenuated. In this case the calculation is only valid for a coverage below one full monolayer (ML) which corresponds to 1.1x10 15 oxygen atoms per cm 2 . Note, that this approach does not account for oxygen atoms that are incorporated into deeper lying lattice planes.…”

Section: Contributedmentioning

confidence: 99%

“…A comprehensive experimental investigation of the reaction of molecular water on GaN(0001)-1×1 surfaces has been reported by Bermudez and Long [2]. They demonstrated that water adsorbs dissociatively on the GaN surface with a sticking coefficient ≥0.45 and a saturation coverage of 0.46 ML.…”

mentioning

confidence: 97%

“…However, the sticking coefficient of water and, hence, the reaction rate was more than two orders of magnitude higher. Especially the initial stages of this fast oxidation process could not be revealed due to the usage of surfaces prepared by nitrogen ion bombardment with a residual oxygen coverage in the range of 0.1 monolayer [2].…”

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confidence: 99%

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Interaction of GaN(0001)‐2×2 surfaces with H₂O

Lorenz

Gutt

Haensel

et al. 2010

Phys. Status Solidi (c)

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We performed an in‐situ analysis of the interaction of water with clean 2×2 reconstructed GaN(0001) surfaces grown by plasma assisted molecular beam epitaxy. The as‐grown surfaces were exposed to molecular water by backfilling. Photoemission spectra reveal an extremely high reactivity and dissociative adsorption with an oxygen sticking coefficient of 0.3 and a saturation coverage of approximately 1 ML. Core level spectra of the O1s state show three individual oxygen components with different temporal behavior. Furthermore, the initial reconstruction quickly vanishes and surface states in the valence band of the as‐grown surface are removed during the exposure of the first few Langmuirs. For higher exposures, two oxygen‐related states appear. The initial upward band bending of 0.4 eV for the as‐grown surface is effectively reduced during oxidation resulting in flat band conditions. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Section: Contributedsupporting

confidence: 70%

Section: Contributedmentioning

confidence: 99%

mentioning

confidence: 97%

mentioning

confidence: 99%

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Interaction of GaN(0001)‐2×2 surfaces with H₂O

Lorenz

Gutt

Haensel

et al. 2010

Phys. Status Solidi (c)

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“…For example, there is evidence that dissociation of H 2 O and O 2 on GaN surfaces introduces O and OH À groups on the surface. 53,54 Removal of this negative charge would thus describe the increase in band bending on the Ga-face as well. It is thus unclear whether the oxygen coverage contributes to the band bending as well, especially on the N face.…”

Section: Discussionmentioning

confidence: 99%

Polarization Effects of GaN and AlGaN: Polarization Bound Charge, Band Bending, and Electronic Surface States

Eller

Yang

Nemanich

2014

Journal of Elec Materi

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Depletion Layer Built‐In Field at (1−100), (0001), and (000−1) GaN/Water Junction and Its Role in Semiconductor Nanowire Water Splitting

Stokowski

Janicki

Serafińczuk

et al. 2019

Adv Materials Inter

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IntroductionFollowing the discovery of semiconductor-based photoelectrolysis by Fujishima and Honda, [1] a considerable attention has been given to this phenomenon as a very promising for clean, sustainable, and storable fuel generation. [2][3][4][5][6] An important aspect of consideration is exploring various kinds of materials and structures to optimize the water-splitting efficiency. The main requirement for the electrode material is a suitable bandgap, which not only allows harvesting the sunlight energyThe nature of specific GaN plane/water interfaces under external bias and illumination can influence photoelectrolysis efficiency using GaN nanowires. Studies of Ga-polar, N-polar, and m-plane GaN interfaces with deionized water allow determining differences between surfaces corresponding to different nanowire facets. They are investigated under external bias conditions to reveal the profile of Fermi level localization through analysis of Franz-Keldysh oscillations using electrolyte electroreflectance (EER) technique in a specially designed measurement chamber. Calculation of the potential barrier height is also possible. EER study shows differences between surface densities of states (SDOS) at distinct GaN planes. One broad SDOS is identified near the conduction band in case of ±c-plane and related to Ga adatom reconstruction and β-Ga 2 O 3 presence at the GaN electrode. Two narrow SDOS singularities are found at the m-plane one of which is localized near the middle of the bandgap and allows to generate approximately two times higher surface potential barrier than in case of polar surfaces at zero-bias conditions. This suggests that n-type GaN nanowires can enhance carrier separation at sidewalls and refine the oxygen evolution rate. Additionally, a voltage-controlled hysteresis loop of Fermi level localization is detected at the Ga-face GaN/water interface.but also is sufficient to overcome overpotentials necessary to split water molecules. One of the most promising materials in this context is gallium nitride, which has been reported useful both as a solid electrode [7] and in a form of nanowire arrays. [8,9] Due to the polar character of the wurtzite crystal structure of GaN, the nature of particular planes in nanowires can differ and result in a change of performance in photoelectrolysis. Especially, the built-in electric field emerging at the surface of GaN brought in a contact with water can have tremendous consequences on photogenerated carriers' separation and their transfer to the surface, where the hydrogen-and oxygen-evolution reactions are driven. The above-mentioned fields and band bending [10] are controlled by the Fermi level pinning at the gallium nitride surface states which are dependent upon the crystal plane choice. [11] In case of wurtzite crystal-based nanowires the most interesting are (0001) c-plane and (1−100) m-plane which usually correspond to the top and side walls of these structures, respectively.Studies of the Fermi level position at semiconductor/water interface can be challeng...

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Chemisorption of H2O on GaN(0001)

Cited by 73 publications

References 34 publications

Interaction of GaN(0001)‐2×2 surfaces with H₂O

Interaction of GaN(0001)‐2×2 surfaces with H₂O

Polarization Effects of GaN and AlGaN: Polarization Bound Charge, Band Bending, and Electronic Surface States

Depletion Layer Built‐In Field at (1−100), (0001), and (000−1) GaN/Water Junction and Its Role in Semiconductor Nanowire Water Splitting

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Chemisorption of H2O on GaN(0001)

Cited by 73 publications

References 34 publications

Interaction of GaN(0001)‐2×2 surfaces with H2O

Interaction of GaN(0001)‐2×2 surfaces with H2O

Polarization Effects of GaN and AlGaN: Polarization Bound Charge, Band Bending, and Electronic Surface States

Depletion Layer Built‐In Field at (1−100), (0001), and (000−1) GaN/Water Junction and Its Role in Semiconductor Nanowire Water Splitting

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Interaction of GaN(0001)‐2×2 surfaces with H₂O

Interaction of GaN(0001)‐2×2 surfaces with H₂O