Photoelectrochemical behaviour of GaAs modified by electrodeposition of heteropolyanions

Allongue, P.; Cachet, H.; Fournier, Michel; Yao, Nan

doi:10.1016/0013-4686(88)80069-0

Cited by 9 publications

(5 citation statements)

References 14 publications

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“…In the dark (single-beam experiment) the smaller values of 8i in presence of Pt suggest that there are less corrosion defects at the surface. This result is consistent with our previous interpretation of these defects which were regarded as oneelectron surface bonds (19); Pt ad-atoms are in fact likely to bring the missing electron and create a much stronger chemical bond as is proved by the position of both states E1 and E~ (they are close to the SC bands). When electronhole pairs are photogenerated (dual beam experiment), the population in the corrosion state depends on the surface.…”

Section: Discussionsupporting

confidence: 93%

“…Figure 3 also shows that AV decreases in 1M NaI while S increases. Such a result is quite similar to that observed with bare n-GaAs photoanodes in contact with variously stabilizing redox couples (19). Reference (19) demonstrates that AV is connected with the remaining photocorrosion of the electrode: the smaller the AV, the smaller the photocorrosion.…”

Section: Resultssupporting

confidence: 82%

“…As a matter of fact, at a naked surface holes are transferred to solution at the top of the valence band (VB) (redox reaction, i.e., stabilization process) and through the corrosion intermediates (photocorrosion process) as it is depicted in Fig. 10a (19); 81 and 82 decrease in Fig. 17b because of a net hole population in the corrosion states.…”

Section: Discussionmentioning

confidence: 99%

“…It must be then considered that the hole also randomly moves parallel to the surface and particularly just below it: this hazardous trajectory must not extend over more than a few kt with respect to its original trajectory towards the interface. Moreover, knowing that the rate constants at the local metal/SC and electrolyte/SC contacts are, respectively, 107 cm/s (22) and 5 • 102 cm/s (19), one finds that a hole needs 71 = 10 14s and 72 = 10 11s to cross the respective interfaces. This means that every hole arriving at the metal-free surface undergoes a great number of collisions in the vicinity of the surface because (i) 7t << 72 and (ii) ~t << %, the lifetime of holes in GaAs.…”

Section: Cbmentioning

confidence: 99%

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Charge Transfer Process at Illuminated Semiconductor/Electrolyte Junctions Modified by Electrodeposition of Microscopic Metal Grain

Allongue

Souteyrand

Allemand

1989

J. Electrochem. Soc.

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Layers made of microscopic Pt grains, optically transparent, with various morphologies are deposited on n-GaAs by electrocrystallization. It is shown that the modified GaAs photoanode is long-term stabilized under illumination in aqueous electrolytes provided that the film presents some required structural properties, e.g., size and density of Pt nuclei. In fact, correlations between the film morphology [studied by transmission electron microscopy (TEM)] and the stabilization of the modified electrode [studied by I-V, C-V measurements and the rotating ring-disk electrode (RRDE) technique] are observed. The mechanism of stabilization by Pt grains is also investigated by.considering the surface state distributions, determined by photocapacitance experiments, at both bare and modified interfaces.The use of n-type narrow bandgap semiconductor/electrolyte (SC/EL) junctions as practical photoelectrochemical (PEC) solar cells is still hampered by the degradation of the photoanode, i.e., the photocorrosion and the chemical attack of the semiconductor. Many years ago photoanodes (Si, GaAs, GAP...) were reported to be effectively protected by vacuum deposition of thin metal layers (1-4), but with some disadvantages: (i) a too large film absorption and (ii) the fact that the modified interface behaves like a semiconductor/metal Schottky barrier dipped in a liquid. Recently the concept of discontinuous metal films makes metal deposition more attractive because such films can be optically transparent (5) and the intrinsic properties of the SC/EL contact (e.g., photovoltage) can be preserved (6). At present discontinuous metal films proved to be suitable for catalyzing the hydrogen photoevolution at p-InP and p-Si (7, 8) and for stabilizing n-Si and n-GaAs in aqueous media (9, 10). Reference (9) puts forward a theory to interpret the spectacular photovoltage of n-Si electrodes modified with a discontinuous metallic film. As the Si metal-free surface is passivated in aqueous media the Pt grains act as the only pathway through the oxide so the invoked catalytic effect is not clear. Considering the above question the present paper intends to bring a better understanding of the role played by the Pt grains. For that purpose we must (i) consider a semiconductor which does not passivate and (ii) be able to vary easily the morphology (density, size of the grains, distribution) of the deposited film. The second point is essential because according to Ref. (9), we expect correlations between the photoelectrochemical behavior of the modified interface (I-V, stabilization...) and the film morphology.The present study deals with the n-GaAs/aqueous electrolyte junction modified by electrodeposition of Pt because GaAs does not passivate in water solution (unless the pH is close to 7); furthermore a previous work in our laboratory suggests that the use of electrocrystallization of Pt on n-GaAs should fulfill the second above requirement because the nucleation and growth modes of the film proved to be easily changed by just modifying some par...

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Section: Discussionsupporting

confidence: 93%

Section: Resultssupporting

confidence: 82%

Section: Discussionmentioning

confidence: 99%

Section: Cbmentioning

confidence: 99%

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Charge Transfer Process at Illuminated Semiconductor/Electrolyte Junctions Modified by Electrodeposition of Microscopic Metal Grain

Allongue

Souteyrand

Allemand

1989

J. Electrochem. Soc.

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“…GaAs is one of the most attractive semiconductor materials used in various electronic devices and dry/wet solar cells. − Scherb and Kolb 23 determined the amounts of electrochemically deposited Cu on n-GaAs(100) by photoreflectivity measurement. Vereecken et al reported the electrochemical behavior of both n- and p-type GaAs(100) in electrolyte solutions containing Cu.…”

Section: Introductionmentioning

confidence: 99%

Structural Study of Electrochemically Deposited Cu on p-GaAs(100) in H₂SO₄ Solution by In Situ Surface-Sensitive X-ray Absorption Fine Structure Measurements

et al. 2000

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The local structures of electrochemically deposited Cu on p-GaAs(100) of various coverages in 0.1 M H 2 SO 4 solution containing 0.1 mM CuSO 4 have been investigated by in situ surface-sensitive X-ray absorption fine structure (XAFS). The Cu K-edge extended X-ray absorption fine structure (EXAFS) and X-ray absorption near-edge structure (XANES) were obtained over a wide range of coverages, i.e., several monolayers down to 1/20 monolayer. The results of multishell parameter fitting of EXAFS data showed that Cu nanoclusters with a short Cu-Cu bond length were formed on the p-GaAs(100) electrode below the critical surface coverage of 0.25 monolayer. The nanoclusters were found to be coordinated with the oxygen atoms of water molecules and/or sulfate anions. They were formed in an early stage of electrochemical deposition and grew in size to approach a densely packed coordination with an fcc structure. XANES spectra showed that the coordination number changed systematically but that a metallic state was retained throughout the electrochemical deposition.

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ChemInform Abstract: Photoelectrochemical Behavior of GaAs Modified by Electrodeposition of Heteropolyanions.

Allongue¹,

Cachet²,

Fournier³

et al. 1988

ChemInform

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ChemInform Abstract Reductive deposition of P2W18O66-2 (P2W18) ions at pH 0 is shown to be an efficient and durable surface modification of n-and p-GaAs electrodes. The treatment induces surface states in the upper and in the lower part of the band gap of GaAs which are responsible for improved H2 evolution and better stability of the photoanodes. The chemical bonds between the substrate and the protonized P2W18 reduced species appear to be very strong.

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Photoelectrochemical behaviour of GaAs modified by electrodeposition of heteropolyanions

Cited by 9 publications

References 14 publications

Charge Transfer Process at Illuminated Semiconductor/Electrolyte Junctions Modified by Electrodeposition of Microscopic Metal Grain

Charge Transfer Process at Illuminated Semiconductor/Electrolyte Junctions Modified by Electrodeposition of Microscopic Metal Grain

Structural Study of Electrochemically Deposited Cu on p-GaAs(100) in H₂SO₄ Solution by In Situ Surface-Sensitive X-ray Absorption Fine Structure Measurements

ChemInform Abstract: Photoelectrochemical Behavior of GaAs Modified by Electrodeposition of Heteropolyanions.

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Photoelectrochemical behaviour of GaAs modified by electrodeposition of heteropolyanions

Cited by 9 publications

References 14 publications

Charge Transfer Process at Illuminated Semiconductor/Electrolyte Junctions Modified by Electrodeposition of Microscopic Metal Grain

Charge Transfer Process at Illuminated Semiconductor/Electrolyte Junctions Modified by Electrodeposition of Microscopic Metal Grain

Structural Study of Electrochemically Deposited Cu on p-GaAs(100) in H2SO4 Solution by In Situ Surface-Sensitive X-ray Absorption Fine Structure Measurements

ChemInform Abstract: Photoelectrochemical Behavior of GaAs Modified by Electrodeposition of Heteropolyanions.

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Structural Study of Electrochemically Deposited Cu on p-GaAs(100) in H₂SO₄ Solution by In Situ Surface-Sensitive X-ray Absorption Fine Structure Measurements