Sulfuration thermique de InP sous pression réduite de vapeur de soufre

Rakib, S.; Gendry, M.; Klopfenstein, P.; Saoudi, Rachida; Durand, J.

doi:10.1016/0040-6090(90)90052-f

Cited by 6 publications

(9 citation statements)

References 11 publications

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“…Then the furnace was heated up to 700 °C with a heating rate of 10 °C min −1 and the sulfur powder at the upstream of the tube was heated to 170 °C. Under this configuration, it is possible to sulfurize the Fe layer at lower temperature with a stable sulfur partial pressure . K‐type thermocouples were used to measure the temperature of the film at the specific distance to the center of the furnace.…”

Section: Methodsmentioning

confidence: 99%

Enhanced Photoresponse of FeS₂ Films: The Role of Marcasite–Pyrite Phase Junctions

Dzade

Gao

et al. 2016

Advanced Materials

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Several possible explanations have been suggested for the low V OC , including bulk non-stoichiometry, [7,[15][16][17] near-surface nonstoichiometry (resulting in a metallic FeS-like surface layer), [18] sulfur vacancies that generate electronic states in the band gap, [13] Fermi level pinning induced by surface states, [19] or small band gap phases (pyrrhotite, troilite, and marcasite) present as domains in bulk pyrite. [8] Orthorhombic marcasite (FeS 2 ) and hexagonal troilite (FeS) are believed to be detrimental phases for photochemical performance, as they have much smaller band gaps (0.04 eV for troilite and 0.34 eV for marcasite), [20] and it has been suggested that even trace amounts of these phases would cause the low V OC reported for pyrite films. [21] The band gap of marcasite was first determined from temperaturedependent (53-370 K) electrical resistivity measurements and a value of 0.34 eV was obtained. [20] However, these measurements were based on the assumption that the carrier mobility is dominated by lattice scattering, [20,22] and the band gap value of marcasite has been rarely verified by other methods, such as optical measurements. Furthermore, several theoretical calculations published in recent years predict that marcasite should have a band gap of 0.8-1.0 eV, which is quite similar to that of pyrite; Gudelli even observed that marcasite has a much larger band gap than pyrite (1.603 eV for marcasite and 1.186 eV for pyrite). [23,24] Very recently, the optical band gap energy of marcasite has been determined by diffuse reflectance spectroscopy to be 0.83 ± 0.02 eV, and the optical absorption of marcasite and pyrite in the near infrared-visible (NIR-Vis) region appears to be quite similar. [25] Therefore, the presence of marcasite is unlikely to undermine the photovoltaic performance of pyrite and it is therefore worth considering whether significant effort should actually be expended on eliminating marcasite traces from pyrite preparations. As the formation of junctions (such as p-n junctions or phase junctions) can efficiently promote charge separation in semiconductor-based photocatalysts, the fabrication of proper junctions in semiconductors is highly desirable in the design and preparation of efficient semiconductor-based photocatalysts. The most conspicuous example is the activity of TiO 2 (P-25, Degussa), which consists of anatase and rutile (4:1 w/w) and exceeds the photocatalytic activity of pure anatase in many reaction systems. [26][27][28][29][30][31][32] Furthermore, Li and co-workers have reported enhanced photocatalytic performance of Ga 2 O 3 with tunable α-β phase junctions. The drastically enhanced activity of mixed α-and β-Ga 2 O 3 over the phase pure oxides was ascribed to efficient charge separation and transfer across the α-β phase junctions. [33][34][35] As to the pyrite-marcasite interface, although most published work has attributed the low performance of pyrite films to the minor presence of marcasite, noThe interest in iron pyrite (cubic FeS 2 ) as a photovoltaic m...

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Section: Methodsmentioning

confidence: 99%

Enhanced Photoresponse of FeS₂ Films: The Role of Marcasite–Pyrite Phase Junctions

Dzade

Gao

et al. 2016

Advanced Materials

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“…Sulfuration of the iron layers has been carried out in a vacuum sealed glass ampule, with sulfur powder (99.99% Merck) inside, placed in a system formed by two different cylindrical furnaces in order to independently regulate the sample and the sulfur source temperatures. Under this configuration, it is possible to control the partial pressure of the S 2 specie near the Fe layer, which seems to be the molecule responsible for the iron sulfuration. ,, The sample is placed in a ceramic holder which is located near the heating resistance of the furnace. This geometric configuration creates a thermal gradient (Δ T /Δ x ∼1.5–2.0 K cm –1 ) along the sample what allows to measure S during the sulfuration process.…”

Section: Methodsmentioning

confidence: 99%

“…Under this configuration, it is possible to control the partial pressure of the S 2 specie near the Fe layer, which seems to be the molecule responsible for the iron sulfuration. 32,41,42 The sample is placed in a ceramic holder which is located near the heating resistance of the furnace. This geometric configuration creates a thermal gradient (ΔT/Δx ∼1.5−2.0 K cm −1 ) along the sample what allows to measure S during the sulfuration process.…”

Section: Methodsmentioning

confidence: 99%

Iron Pyrite from Iron Thin Films: Identification of Intermediate Phases and Associated Conductivity-type Transitions

et al. 2014

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In this work, the growth of FeS 2 by direct sulfuration of Fe thin films is examined with the purpose of elucidating the nature of the Fe to FeS 2 transformation and to state some of its characteristics. To this aim, the film Seebeck coefficient (S) was measured during the whole sulfuration treatment. The S value changes from positive (ca. +8 μV K −1 ) to negative values (ca. −15 μV K −1 ) and, then, to very positive (ca. +100 μV K −1 ) at the end of the sulfuration process. To understand the film transformations and the resulting S evolution (mainly, the cause of its negative values) some Fe films were sulfurated during some selected times and, then, quickly cooled (to prevent changes in the chemical composition of the films) from the corresponding sulfuration temperature to room temperature (RT). Chemical composition and structural analyses of the quenched samples were accomplished at RT. Using the obtained data, it was concluded that the sulfuration transforms the original Fe film into hexagonal pyrrhotite (Fe 1−x S H ), which partially converts to its orthorhombic (Fe 1−x S O ) phase through a Neél transformation. Then, both the orthorhombic and hexagonal pyrrhotites react with sulfur to form pyrite (FeS 2 ). These chemical transformations are accompanied by changes of the film conductivity type: from p-type (Fe) to n-type (pyrrhotites) and finally to p-type (FeS 2 ). The intermediate pyrrhotite phases appear to be precursors of the final pyrite phase. Results are discussed in the light of former data on sulfurated thin films and Fe bulk samples.

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“…T SA was increased linearly at a rate of 100 K/h up to 600 K while T SU rises up to 350 K. At T SA ) 475 K, the vapor in the sample compartment is mainly composed of S 2 , reaching maximum pressure, P T ) P S2 ) 5 × 10 -4 mbar, at T SA ) 600 K. The enrichment of the sulfur vapor in S 2 molecules favors the sulfuration process, since the S 2 molecule is the active species in metal sulfuration processes. 17 The meaning of the continuous vertical lines indicating samples from "a" to "d" will be explained in the Results Section. The film is placed in the sample compartment between two ceramic foils of the sample holder, which is provided with four stainless steel electrical contacts.…”

Section: Methodsmentioning

confidence: 99%

“…Figure shows the time evolution of T SU , T SA , P T , and P S2 during a typical experiment. T SA was increased linearly at a rate of 100 K/h up to 600 K while T SU rises up to 350 K. At T SA = 475 K, the vapor in the sample compartment is mainly composed of S 2 , reaching maximum pressure, P T = P S2 = 5 × 10 −4 mbar, at T SA = 600 K. The enrichment of the sulfur vapor in S 2 molecules favors the sulfuration process, since the S 2 molecule is the active species in metal sulfuration processes . The meaning of the continuous vertical lines indicating samples from “a” to “d” will be explained in the Results Section.…”

Section: Methodsmentioning

confidence: 99%

Cubic Pd₁₆S₇ as a Precursor Phase in the Formation of Tetragonal PdS by Sulfuration of Pd Thin Films

et al. 2009

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Experimental results are reported showing that sulfuration of metallic Pd thin films gives rise to Pd16S7, which finally, transforms into tetragonal PdS. The whole process has been investigated by measuring the film electrical resistance while increasing its temperature and the sulfur vapor pressure. At temperatures T ≈ 460 K and pressures P S2 ≈ 10−6 mbar, Pd is already fully transformed into Pd16S7. Obtained Pd16S7 nanocrystalline films (50 nm crystallite size) have been characterized (morphological, structural, optical, and transport properties at room temperature (RT)) for the first time. They show a cubic structure with a lattice parameter a = 8.921 ± 0.009 Å, an electrical resistivity ρ = 7.2 × 10−4 Ω·cm, and a Seebeck coefficient S = 11.8 μV/K. Their optical absorption coefficient is almost constant for photon energies in the range 1−3 eV. On increasing the temperature and sulfur pressure, Pd16S7 gives rise to nanocrystalline PdS thin films (30−40 nm crystallite size) with an n-type semiconducting behavior, having an electrical resistivity ρ = 5.6 × 10−2 Ω·cm and an a Seebeck coefficient S = −268 μV/K at RT. The optical absorption measurements indicate that the absorption edge of PdS is due to two allowed direct transitions with E G ≈ 1.45 and 1.70 eV, respectively. Finally, obtained results are discussed on the light of thermodynamic calculations, which confirm the sequence of sulfides formation described in the paper. The possible interest of PdS in thermoelectric applications is emphasized.

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Sulfuration thermique de InP sous pression réduite de vapeur de soufre

Cited by 6 publications

References 11 publications

Enhanced Photoresponse of FeS₂ Films: The Role of Marcasite–Pyrite Phase Junctions

Enhanced Photoresponse of FeS₂ Films: The Role of Marcasite–Pyrite Phase Junctions

Iron Pyrite from Iron Thin Films: Identification of Intermediate Phases and Associated Conductivity-type Transitions

Cubic Pd₁₆S₇ as a Precursor Phase in the Formation of Tetragonal PdS by Sulfuration of Pd Thin Films

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Sulfuration thermique de InP sous pression réduite de vapeur de soufre

Cited by 6 publications

References 11 publications

Enhanced Photoresponse of FeS2 Films: The Role of Marcasite–Pyrite Phase Junctions

Enhanced Photoresponse of FeS2 Films: The Role of Marcasite–Pyrite Phase Junctions

Iron Pyrite from Iron Thin Films: Identification of Intermediate Phases and Associated Conductivity-type Transitions

Cubic Pd16S7 as a Precursor Phase in the Formation of Tetragonal PdS by Sulfuration of Pd Thin Films

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Enhanced Photoresponse of FeS₂ Films: The Role of Marcasite–Pyrite Phase Junctions

Enhanced Photoresponse of FeS₂ Films: The Role of Marcasite–Pyrite Phase Junctions

Cubic Pd₁₆S₇ as a Precursor Phase in the Formation of Tetragonal PdS by Sulfuration of Pd Thin Films