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Wolfram Jaegermann - One of the best experts on this subject based on the ideXlab platform.
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Photoelectrochemical Processes at n-GaAs(100)/Aqueous HCl Electrolyte Interface: A Synchrotron Photoemission Spectroscopy Study of Emersed Electrodes
The Journal of Physical Chemistry C, 2014Co-Authors: Mikhail V. Lebedev, Thomas Mayer, Wolfram Calvet, Wolfram JaegermannAbstract:High-resolution synchrotron photoemission spectroscopy has been applied to detail the electrochemical and photoelectrochemical corrosion reactions at the liquid junction n-GaAs(100)/1 M aqueous HCl solution. Under anodic polarization of 1.8 eV, the main process initiated by the presence of holes in the Ga–As bonding states of the valence band is the formation of soluble gallium chloride complexes and insoluble Elemental Arsenic on the surface. In addition, Arsenic hydroxide forms, which reacts further to soluble HAsO2. In toto, the As/Ga atomic ratio increases, which is accompanied by an increase of the work function. The anodic decomposition reaction is enhanced by illumination as more holes reach the n-semiconductor/electrolyte junction. Under cathodic polarization of 1.5 eV, only minor changes are observed in Ga and As core-level spectra, giving no indication of corrosion, but specific adsorption of hydrated HCl molecules and/or Cl– ions considerably modifies valence band spectra.
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Etching of GaAs(100) with Aqueous Ammonia Solution: A Synchrotron-Photoemission Spectroscopy Study
The Journal of Physical Chemistry C, 2010Co-Authors: Mikhail V. Lebedev, Thomas Mayer, Eric Mankel, Wolfram JaegermannAbstract:Etching of the GaAs(100) surface with aqueous ammonia solution is studied by highly surface-sensitive synchrotron-radiation photoemission spectroscopy. It is shown that such treatment effectively removes the native oxide layer leaving the surface covered with Elemental Arsenic, as well as Arsenic hydroxides AsOH and As(OH)3, gallium hydroxide GaOH, and gallium suboxide GaxO. After annealing of the surface at 500 °C, the Arsenic and gallium hydroxides disappear, while the excess Arsenic is dimerized. The residual carbon contamination prevents disappearance of gallium hydroxide and hinders dimerization of excess Arsenic on annealing. Rinsing the etched surface with 2-propanol instead of water prior to annealing results in considerable reduction of carbon contamination after annealing.
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SXPS study of model GaAs(100)/electrolyte interface
physica status solidi (c), 2010Co-Authors: Mikhail V. Lebedev, Thomas Mayer, Eric Mankel, Wolfram JaegermannAbstract:Model GaAs(100)/electrolyte interfaces are prepared in vacuum by co-adsorption of Cl2 and 2-propanol molecules at LN2 temperature. On adsorption of Cl2 molecules gallium chlorides, Elemental Arsenic and Arsenic chlorides are formed. Co-adsorption of 2-propanol causes formation of additional GaCl3 and AsCl, as well as soluble/volatile As-based complexes, which are released from the surface depleting the sur- face by Arsenic. Comparison of the As 3d and Ga 3d spectra obtained after heating the model interface to room temperature with the corresponding spectra obtained after emersion of the GaAs(100) surface from HCl/2-propanol solution allows to conclude that in HCl solution Cl– ions attack gallium sites and H+ ions mostly attack Arsenic sites. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
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Wet Etching of GaAs(100) in Acidic and Basic Solutions : A Synchrotron-Photoemission Spectroscopy Study
The Journal of Physical Chemistry C, 2008Co-Authors: Mikhail V. Lebedev, Thomas Mayer, Eric Mankel, Wolfram JaegermannAbstract:The interaction of the oxide-free GaAs(100) surface with acidic (HCl + 2-propanol) and basic (aqueous NH3) solutions is studied by synchrotron−photoemission spectroscopy. It is found that both solutions attack mostly surface gallium atoms and form weakly soluble gallium chlorides and soluble gallium hydroxides, respectively. Thereby, Ga−As bonds at the surface are broken, and Elemental Arsenic is left behind on the GaAs surface. In addition, adsorbed 2-propanol molecules are observed on etching with HCl + 2-propanol solution, but no adsorbed water molecules are detected on etching with aqueous ammonia solution.
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Synchrotron Photoemission Analysis of Semiconductor/Electrolyte Interfaces by the Frozen-Electrolyte Approach: Interaction of HCl in 2-Propanol with GaAs(100)
The journal of physical chemistry. B, 2006Co-Authors: Thomas Mayer, Mikhail V. Lebedev, Ralf Hunger, Wolfram JaegermannAbstract:Perspectives of a new approach for the synchrotron photoemission spectroscopic analysis of chemical processes at solid/liquid interfaces under UHV conditions have been explored. A thin layer of HCl-2-propanol solution was frozen-in on the semiconductor GaAs(100) wafer surface by cooling the substrate to liquid nitrogen temperature after etching off the native oxide layer under N2 atmosphere. Chemical reactions induced in situ by exposure to synchrotron radiation (SR) and by stepwise heating have been monitored. Right after etching and freezing, the surface is covered by gallium chlorides with 1, 2, 3, and 4 Cl ions attached and lattice back-bonded to As atoms, as well as by Elemental Arsenic As0 and 2-propanol. Exposure to SR at low temperature produces surface As chlorides at the expense of As0. The GaCl3 and GaCl2 emissions diminish while GaCl is enhanced. On the other hand, heating the sample to approximately 130 K just above H2O desorption causes the thermodynamically expected reaction of AsCl3 with the substrate GaAs to form Ga chloride species and As0. Heating the sample to room temperature leaves only As0 on the surface and for gallium the content of all surface chlorides is drastically reduced. By further heating to 400 K Elemental Arsenic starts to desorb and the Ga chloride surface content is reduced. Using different excitation energies the depth composition of the reaction products has been monitored indicating a tendency of decreasing chlorination numbers and increasing Ga vs As chloride content toward the pristine substrate at each stage of the reaction.
Mikhail V. Lebedev - One of the best experts on this subject based on the ideXlab platform.
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Photoelectrochemical Processes at n-GaAs(100)/Aqueous HCl Electrolyte Interface: A Synchrotron Photoemission Spectroscopy Study of Emersed Electrodes
The Journal of Physical Chemistry C, 2014Co-Authors: Mikhail V. Lebedev, Thomas Mayer, Wolfram Calvet, Wolfram JaegermannAbstract:High-resolution synchrotron photoemission spectroscopy has been applied to detail the electrochemical and photoelectrochemical corrosion reactions at the liquid junction n-GaAs(100)/1 M aqueous HCl solution. Under anodic polarization of 1.8 eV, the main process initiated by the presence of holes in the Ga–As bonding states of the valence band is the formation of soluble gallium chloride complexes and insoluble Elemental Arsenic on the surface. In addition, Arsenic hydroxide forms, which reacts further to soluble HAsO2. In toto, the As/Ga atomic ratio increases, which is accompanied by an increase of the work function. The anodic decomposition reaction is enhanced by illumination as more holes reach the n-semiconductor/electrolyte junction. Under cathodic polarization of 1.5 eV, only minor changes are observed in Ga and As core-level spectra, giving no indication of corrosion, but specific adsorption of hydrated HCl molecules and/or Cl– ions considerably modifies valence band spectra.
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Etching of GaAs(100) with Aqueous Ammonia Solution: A Synchrotron-Photoemission Spectroscopy Study
The Journal of Physical Chemistry C, 2010Co-Authors: Mikhail V. Lebedev, Thomas Mayer, Eric Mankel, Wolfram JaegermannAbstract:Etching of the GaAs(100) surface with aqueous ammonia solution is studied by highly surface-sensitive synchrotron-radiation photoemission spectroscopy. It is shown that such treatment effectively removes the native oxide layer leaving the surface covered with Elemental Arsenic, as well as Arsenic hydroxides AsOH and As(OH)3, gallium hydroxide GaOH, and gallium suboxide GaxO. After annealing of the surface at 500 °C, the Arsenic and gallium hydroxides disappear, while the excess Arsenic is dimerized. The residual carbon contamination prevents disappearance of gallium hydroxide and hinders dimerization of excess Arsenic on annealing. Rinsing the etched surface with 2-propanol instead of water prior to annealing results in considerable reduction of carbon contamination after annealing.
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SXPS study of model GaAs(100)/electrolyte interface
physica status solidi (c), 2010Co-Authors: Mikhail V. Lebedev, Thomas Mayer, Eric Mankel, Wolfram JaegermannAbstract:Model GaAs(100)/electrolyte interfaces are prepared in vacuum by co-adsorption of Cl2 and 2-propanol molecules at LN2 temperature. On adsorption of Cl2 molecules gallium chlorides, Elemental Arsenic and Arsenic chlorides are formed. Co-adsorption of 2-propanol causes formation of additional GaCl3 and AsCl, as well as soluble/volatile As-based complexes, which are released from the surface depleting the sur- face by Arsenic. Comparison of the As 3d and Ga 3d spectra obtained after heating the model interface to room temperature with the corresponding spectra obtained after emersion of the GaAs(100) surface from HCl/2-propanol solution allows to conclude that in HCl solution Cl– ions attack gallium sites and H+ ions mostly attack Arsenic sites. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
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Wet Etching of GaAs(100) in Acidic and Basic Solutions : A Synchrotron-Photoemission Spectroscopy Study
The Journal of Physical Chemistry C, 2008Co-Authors: Mikhail V. Lebedev, Thomas Mayer, Eric Mankel, Wolfram JaegermannAbstract:The interaction of the oxide-free GaAs(100) surface with acidic (HCl + 2-propanol) and basic (aqueous NH3) solutions is studied by synchrotron−photoemission spectroscopy. It is found that both solutions attack mostly surface gallium atoms and form weakly soluble gallium chlorides and soluble gallium hydroxides, respectively. Thereby, Ga−As bonds at the surface are broken, and Elemental Arsenic is left behind on the GaAs surface. In addition, adsorbed 2-propanol molecules are observed on etching with HCl + 2-propanol solution, but no adsorbed water molecules are detected on etching with aqueous ammonia solution.
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Synchrotron Photoemission Analysis of Semiconductor/Electrolyte Interfaces by the Frozen-Electrolyte Approach: Interaction of HCl in 2-Propanol with GaAs(100)
The journal of physical chemistry. B, 2006Co-Authors: Thomas Mayer, Mikhail V. Lebedev, Ralf Hunger, Wolfram JaegermannAbstract:Perspectives of a new approach for the synchrotron photoemission spectroscopic analysis of chemical processes at solid/liquid interfaces under UHV conditions have been explored. A thin layer of HCl-2-propanol solution was frozen-in on the semiconductor GaAs(100) wafer surface by cooling the substrate to liquid nitrogen temperature after etching off the native oxide layer under N2 atmosphere. Chemical reactions induced in situ by exposure to synchrotron radiation (SR) and by stepwise heating have been monitored. Right after etching and freezing, the surface is covered by gallium chlorides with 1, 2, 3, and 4 Cl ions attached and lattice back-bonded to As atoms, as well as by Elemental Arsenic As0 and 2-propanol. Exposure to SR at low temperature produces surface As chlorides at the expense of As0. The GaCl3 and GaCl2 emissions diminish while GaCl is enhanced. On the other hand, heating the sample to approximately 130 K just above H2O desorption causes the thermodynamically expected reaction of AsCl3 with the substrate GaAs to form Ga chloride species and As0. Heating the sample to room temperature leaves only As0 on the surface and for gallium the content of all surface chlorides is drastically reduced. By further heating to 400 K Elemental Arsenic starts to desorb and the Ga chloride surface content is reduced. Using different excitation energies the depth composition of the reaction products has been monitored indicating a tendency of decreasing chlorination numbers and increasing Ga vs As chloride content toward the pristine substrate at each stage of the reaction.
Thomas Mayer - One of the best experts on this subject based on the ideXlab platform.
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Photoelectrochemical Processes at n-GaAs(100)/Aqueous HCl Electrolyte Interface: A Synchrotron Photoemission Spectroscopy Study of Emersed Electrodes
The Journal of Physical Chemistry C, 2014Co-Authors: Mikhail V. Lebedev, Thomas Mayer, Wolfram Calvet, Wolfram JaegermannAbstract:High-resolution synchrotron photoemission spectroscopy has been applied to detail the electrochemical and photoelectrochemical corrosion reactions at the liquid junction n-GaAs(100)/1 M aqueous HCl solution. Under anodic polarization of 1.8 eV, the main process initiated by the presence of holes in the Ga–As bonding states of the valence band is the formation of soluble gallium chloride complexes and insoluble Elemental Arsenic on the surface. In addition, Arsenic hydroxide forms, which reacts further to soluble HAsO2. In toto, the As/Ga atomic ratio increases, which is accompanied by an increase of the work function. The anodic decomposition reaction is enhanced by illumination as more holes reach the n-semiconductor/electrolyte junction. Under cathodic polarization of 1.5 eV, only minor changes are observed in Ga and As core-level spectra, giving no indication of corrosion, but specific adsorption of hydrated HCl molecules and/or Cl– ions considerably modifies valence band spectra.
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Etching of GaAs(100) with Aqueous Ammonia Solution: A Synchrotron-Photoemission Spectroscopy Study
The Journal of Physical Chemistry C, 2010Co-Authors: Mikhail V. Lebedev, Thomas Mayer, Eric Mankel, Wolfram JaegermannAbstract:Etching of the GaAs(100) surface with aqueous ammonia solution is studied by highly surface-sensitive synchrotron-radiation photoemission spectroscopy. It is shown that such treatment effectively removes the native oxide layer leaving the surface covered with Elemental Arsenic, as well as Arsenic hydroxides AsOH and As(OH)3, gallium hydroxide GaOH, and gallium suboxide GaxO. After annealing of the surface at 500 °C, the Arsenic and gallium hydroxides disappear, while the excess Arsenic is dimerized. The residual carbon contamination prevents disappearance of gallium hydroxide and hinders dimerization of excess Arsenic on annealing. Rinsing the etched surface with 2-propanol instead of water prior to annealing results in considerable reduction of carbon contamination after annealing.
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SXPS study of model GaAs(100)/electrolyte interface
physica status solidi (c), 2010Co-Authors: Mikhail V. Lebedev, Thomas Mayer, Eric Mankel, Wolfram JaegermannAbstract:Model GaAs(100)/electrolyte interfaces are prepared in vacuum by co-adsorption of Cl2 and 2-propanol molecules at LN2 temperature. On adsorption of Cl2 molecules gallium chlorides, Elemental Arsenic and Arsenic chlorides are formed. Co-adsorption of 2-propanol causes formation of additional GaCl3 and AsCl, as well as soluble/volatile As-based complexes, which are released from the surface depleting the sur- face by Arsenic. Comparison of the As 3d and Ga 3d spectra obtained after heating the model interface to room temperature with the corresponding spectra obtained after emersion of the GaAs(100) surface from HCl/2-propanol solution allows to conclude that in HCl solution Cl– ions attack gallium sites and H+ ions mostly attack Arsenic sites. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
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Wet Etching of GaAs(100) in Acidic and Basic Solutions : A Synchrotron-Photoemission Spectroscopy Study
The Journal of Physical Chemistry C, 2008Co-Authors: Mikhail V. Lebedev, Thomas Mayer, Eric Mankel, Wolfram JaegermannAbstract:The interaction of the oxide-free GaAs(100) surface with acidic (HCl + 2-propanol) and basic (aqueous NH3) solutions is studied by synchrotron−photoemission spectroscopy. It is found that both solutions attack mostly surface gallium atoms and form weakly soluble gallium chlorides and soluble gallium hydroxides, respectively. Thereby, Ga−As bonds at the surface are broken, and Elemental Arsenic is left behind on the GaAs surface. In addition, adsorbed 2-propanol molecules are observed on etching with HCl + 2-propanol solution, but no adsorbed water molecules are detected on etching with aqueous ammonia solution.
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Synchrotron Photoemission Analysis of Semiconductor/Electrolyte Interfaces by the Frozen-Electrolyte Approach: Interaction of HCl in 2-Propanol with GaAs(100)
The journal of physical chemistry. B, 2006Co-Authors: Thomas Mayer, Mikhail V. Lebedev, Ralf Hunger, Wolfram JaegermannAbstract:Perspectives of a new approach for the synchrotron photoemission spectroscopic analysis of chemical processes at solid/liquid interfaces under UHV conditions have been explored. A thin layer of HCl-2-propanol solution was frozen-in on the semiconductor GaAs(100) wafer surface by cooling the substrate to liquid nitrogen temperature after etching off the native oxide layer under N2 atmosphere. Chemical reactions induced in situ by exposure to synchrotron radiation (SR) and by stepwise heating have been monitored. Right after etching and freezing, the surface is covered by gallium chlorides with 1, 2, 3, and 4 Cl ions attached and lattice back-bonded to As atoms, as well as by Elemental Arsenic As0 and 2-propanol. Exposure to SR at low temperature produces surface As chlorides at the expense of As0. The GaCl3 and GaCl2 emissions diminish while GaCl is enhanced. On the other hand, heating the sample to approximately 130 K just above H2O desorption causes the thermodynamically expected reaction of AsCl3 with the substrate GaAs to form Ga chloride species and As0. Heating the sample to room temperature leaves only As0 on the surface and for gallium the content of all surface chlorides is drastically reduced. By further heating to 400 K Elemental Arsenic starts to desorb and the Ga chloride surface content is reduced. Using different excitation energies the depth composition of the reaction products has been monitored indicating a tendency of decreasing chlorination numbers and increasing Ga vs As chloride content toward the pristine substrate at each stage of the reaction.
Cg Salzmann - One of the best experts on this subject based on the ideXlab platform.
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One‐Dimensional Arsenic Allotropes: Polymerization of Yellow Arsenic Inside Single‐Wall Carbon Nanotubes
WILEY-V C H VERLAG GMBH, 2018Co-Authors: Hart M, Chen J, Michaelides A, Sella A, Shaffer Msp, Cg SalzmannAbstract:The pnictogen nanomaterials, including phosphorene and arsenene, display remarkable electronic and chemical properties. Yet, the structural diversity of these main group elements is still poorly explored. Here we fill single‐wall carbon nanotubes with Elemental Arsenic from the vapor phase. Using electron microscopy, we find chains of highly reactive As4 molecules as well as two new one‐dimensional allotropes of Arsenic: a single‐stranded zig‐zag chain and a double‐stranded zig‐zag ladder. These linear structures are important intermediates between the gas‐phase clusters of Arsenic and the extended sheets of arsenene. Raman spectroscopy indicates weak electronic interaction between the Arsenic and the nanotubes which implies that the formation of the new allotropes is driven primarily by the geometry of the confinement. The relative stabilities of the new Arsenic structures are estimated computationally. Band‐gap calculations predict that the insulating As₄ chains become semiconducting, once converted to the zig‐zag ladder, and form a fully metallic allotrope of Arsenic as the zig‐zag chain
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One-dimensional Arsenic allotropes: polymerization of yellow Arsenic inside single-wall carbon nanotubes
'Wiley', 2018Co-Authors: Hart M, Chen J, Michaelides A, Sella A, Shaffer Msp, Cg SalzmannAbstract:The pnictogen nanomaterials, including phosphorene and arsenene, display remarkable electronic and chemical properties. Yet, the structural diversity of these main group elements is still poorly explored. Here we fill single‐wall carbon nanotubes with Elemental Arsenic from the vapor phase. Using electron microscopy, we find chains of highly reactive As4 molecules as well as two new one‐dimensional allotropes of Arsenic: a single‐stranded zig‐zag chain and a double‐stranded zig‐zag ladder. These linear structures are important intermediates between the gas‐phase clusters of Arsenic and the extended sheets of arsenene. Raman spectroscopy indicates weak electronic interaction between the Arsenic and the nanotubes which implies that the formation of the new allotropes is driven primarily by the geometry of the confinement. The relative stabilities of the new Arsenic structures are estimated computationally. Band‐gap calculations predict that the insulating As4 chains become semiconducting, once converted to the zig‐zag ladder, and form a fully metallic allotrope of Arsenic as the zig‐zag chain
Eric Mankel - One of the best experts on this subject based on the ideXlab platform.
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Etching of GaAs(100) with Aqueous Ammonia Solution: A Synchrotron-Photoemission Spectroscopy Study
The Journal of Physical Chemistry C, 2010Co-Authors: Mikhail V. Lebedev, Thomas Mayer, Eric Mankel, Wolfram JaegermannAbstract:Etching of the GaAs(100) surface with aqueous ammonia solution is studied by highly surface-sensitive synchrotron-radiation photoemission spectroscopy. It is shown that such treatment effectively removes the native oxide layer leaving the surface covered with Elemental Arsenic, as well as Arsenic hydroxides AsOH and As(OH)3, gallium hydroxide GaOH, and gallium suboxide GaxO. After annealing of the surface at 500 °C, the Arsenic and gallium hydroxides disappear, while the excess Arsenic is dimerized. The residual carbon contamination prevents disappearance of gallium hydroxide and hinders dimerization of excess Arsenic on annealing. Rinsing the etched surface with 2-propanol instead of water prior to annealing results in considerable reduction of carbon contamination after annealing.
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SXPS study of model GaAs(100)/electrolyte interface
physica status solidi (c), 2010Co-Authors: Mikhail V. Lebedev, Thomas Mayer, Eric Mankel, Wolfram JaegermannAbstract:Model GaAs(100)/electrolyte interfaces are prepared in vacuum by co-adsorption of Cl2 and 2-propanol molecules at LN2 temperature. On adsorption of Cl2 molecules gallium chlorides, Elemental Arsenic and Arsenic chlorides are formed. Co-adsorption of 2-propanol causes formation of additional GaCl3 and AsCl, as well as soluble/volatile As-based complexes, which are released from the surface depleting the sur- face by Arsenic. Comparison of the As 3d and Ga 3d spectra obtained after heating the model interface to room temperature with the corresponding spectra obtained after emersion of the GaAs(100) surface from HCl/2-propanol solution allows to conclude that in HCl solution Cl– ions attack gallium sites and H+ ions mostly attack Arsenic sites. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
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Wet Etching of GaAs(100) in Acidic and Basic Solutions : A Synchrotron-Photoemission Spectroscopy Study
The Journal of Physical Chemistry C, 2008Co-Authors: Mikhail V. Lebedev, Thomas Mayer, Eric Mankel, Wolfram JaegermannAbstract:The interaction of the oxide-free GaAs(100) surface with acidic (HCl + 2-propanol) and basic (aqueous NH3) solutions is studied by synchrotron−photoemission spectroscopy. It is found that both solutions attack mostly surface gallium atoms and form weakly soluble gallium chlorides and soluble gallium hydroxides, respectively. Thereby, Ga−As bonds at the surface are broken, and Elemental Arsenic is left behind on the GaAs surface. In addition, adsorbed 2-propanol molecules are observed on etching with HCl + 2-propanol solution, but no adsorbed water molecules are detected on etching with aqueous ammonia solution.