M. Aggour | Ibn Tofail University (original) (raw)

Papers by M. Aggour

Research paper thumbnail of Electrochemically Induced Self-organized Nanostructures on Silicon for Realization of a Novel Nanoemitter Solar Cell Concept

ECS Transactions, 2007

Oscillatory behaviour of silicon electrodes in fluoride containing solution results in formation ... more Oscillatory behaviour of silicon electrodes in fluoride containing solution results in formation of nanoporous oxides. Metal electrodeposition into these pores results in local Schottky junction formation. Metal nanoemitters are contacted with a transparent conductive oxide and aluminum contact fingers for preparation of the first device (Al/ZnO/Pt-SiO 2 /Si/GaIn/Ag). Present solar-toelectrical conversion efficiencies are small and various improvement possibilities are outlined.

Research paper thumbnail of Interface condition of n-Si(111) during photocurrent oscillations in NH4F solutions

Journal of Electroanalytical Chemistry, 1995

ABSTRACT

Research paper thumbnail of Efficient photoelectrochemical nanoemitter solar cell

Electrochemistry Communications, 2008

Photoelectrochemical solar cells convert solar energy into electricity as fuels . The operation i... more Photoelectrochemical solar cells convert solar energy into electricity as fuels . The operation is based on the contact potential between a semiconductor and a redox electrolyte that results in the separation of photoinduced excess charge carriers. The applicability of photoelectrochemical solar energy conversion, however, is limited by photocorrosion at the reactive interface. Here, a new efficient photoelectrochemical solar cell is reported that avoids contact between semiconductor and electrolyte. The operational principle is based on metallic nanoemitters that form local contacts between the semiconductor absorber and the redox electrolyte while the remaining semiconductor surface is covered by an insulating anodic oxide. The nanoporous oxide, prepared by an oscillatory self-organised electrochemical process, serves as a template for spatially selective metal nanoemitter electrodeposition, resulting in a Si/SiO 2 /Pt nanocomposite structure after Pt deposition. In contact with I À =I À 3 redox electrolyte, a solar conversion efficiency of 11.2% has been obtained with the cell n À Si=SiO 2 =Pt=I À =I À 3 =C. The novel concept is characterized by the scalability of the employed oscillatory process, low-temperature processing, protection of the semiconductor surface from the solution and applicability in monolithically integrated solar fuel generating devices (photoelectrocatalysis) and solid-state solar cells.

Research paper thumbnail of Growth and characterization of ZnO thin films prepared by electrodeposition technique

Solar Energy Materials and Solar Cells, 2006

ZnO thin films were deposited on either indium tin oxide-coated glass or copper substrate by the ... more ZnO thin films were deposited on either indium tin oxide-coated glass or copper substrate by the electrodeposition process, using zinc chloride and flowing air as precursors. The effect of pH on the structural and morphological ZnO films was studied and the optimum deposition conditions have been outlined. The kinetics of the growth of the films have been investigated. We note that the rate of deposition of ZnO in an acidic solution was larger than in a basic solution. The structure of the films was studied using X-ray diffractometry (XRD) and transmission electron microscopy (TEM). The surface morphology and thickness of the films were determined using scanning electron microscopy. The X-ray diffraction analysis shows that the films are polycrystalline with hexagonal crystal structure (zincite) at pH 4. The optical transmittance of ZnO decreases with varying film thickness. The optical energy bandgap was found to be 3.26 eV.

Research paper thumbnail of Anodic preparation of porous TiO2 in fluoride solution

physica status solidi (c), 2005

Thick and homogeneous layers of porous TiO 2 (anatase and amorphous phases) have been prepared by... more Thick and homogeneous layers of porous TiO 2 (anatase and amorphous phases) have been prepared by anodization of Ti foils in fluoride solutions. The porous TiO 2 layers have been investigated by electron microscopy, Raman spectroscopy and photovoltage spectroscopy. The nanostructure of the porous TiO 2 layers depends sensitively on the pH and on the concentration of the NH 4 F solution. The photovoltage spectra of as-prepared samples are dominated by defects (electron traps) below the bandgap of anatase. The defects are removed after annealing in air.

Research paper thumbnail of Etch Rates of Anodic Silicon Oxides in Dilute Fluoride Solutions

Journal of The Electrochemical Society, 2003

ABSTRACT

Research paper thumbnail of High resolution surface analysis of Si roughening in dilute ammonium fluoride solution

Journal of Electroanalytical Chemistry, 2003

The initial stages of porous Si formation on Si(111) in dilute ammonium fluoride solution are ana... more The initial stages of porous Si formation on Si(111) in dilute ammonium fluoride solution are analysed by photoelectron spectroscopy using synchrotron radiation (SRPES). The PES results in the por-Si formation regime partly support a recent dissolution model. The contribution from the Si 2p surface core level shift shows that 0.35 ML of the surface is still H-terminated after interruption of the conditioning process at the first photocurrent maximum. Two signals shifted in binding energy by 0.8 and 1 eV, respectively, are attributed to reaction intermediates expected from the proposed reaction mechanism and from theoretical calculations using density functional theory (DFT). A distinct roughening is found in in-situ AFM measurements, with a calculated RMS roughness parameter of 2.6 nm. # 2002 Published by Elsevier Science B.V.

Research paper thumbnail of Electrochemical Method for Evaluation of Structural Perfection of Hydrogen-Terminated Si(111) Surface

Japanese Journal of Applied Physics, 2000

Abstract In this study, we measured the electrochemical oxidation currents on n-Si (111) surfaces... more Abstract In this study, we measured the electrochemical oxidation currents on n-Si (111) surfaces at a potential near the flat-band potential. The current became small when the surface was treated with oxygen-free water, which is effective for flattening the Si (111) ...

Research paper thumbnail of One, step electrodeposition of Cu(Ga,In)Se 2 thin films from aqueous solution

Journal de Physique IV (Proceedings), 2005

Cu(In,Ga)Se{2} (CIGS) semiconducting thin films films were prepared by electrodeposition from aqu... more Cu(In,Ga)Se{2} (CIGS) semiconducting thin films films were prepared by electrodeposition from aqueous solution containing CuCl{2}, InCl{3}, GaCl{3} and H{2}SeO{3}. The deposited material was characterized by cyclic voltammetry. The compositional, structural studies were carried out using scanning electron microscopy (SEM), energy dispersive X-ray microanalysis (EDX), X-ray diffraction (XRD) and transmission electron microscopy (TEM). X-ray analysis showed the formation of CuIn{1-x}GaxSe{2} films,

Research paper thumbnail of Photoactive nanostructure device by electrochemical processing of silicon

Journal of Electroanalytical Chemistry, 2008

The realization of a photoactive Si-based device that operates in the photovoltaic as well as in ... more The realization of a photoactive Si-based device that operates in the photovoltaic as well as in the photoelectrocatalytic mode is described. The system is based on self organized nanopore formation in the anodic silicon oxide which is present during current oscillations in fluoride containing electrolytes. Electrodeposition of Schottky barrier and/or catalytic metals into the pores forms nanoemitter contacts. In contact with redox electrolytes, comparably efficient photoelectrochemical solar energy conversion is obtained. With n-type Si, solar-to-electricity conversion efficiencies are between 6% and 7%. For illuminated p-Si, hydrogen evolution is observed. Present limitations in efficiencies are attributed to the non-optimized pore metallization process and reduced interface electronic quality for the photovoltaic system. For p-Si, the low contact potential difference between its Fermi level and the electrochemical potential for hydrogen evolution limits the attainable photovoltage. Routes for improvement of both devices are outlined.

Research paper thumbnail of Electrochemically Induced Self-organized Nanostructures on Silicon for Realization of a Novel Nanoemitter Solar Cell Concept

ECS Transactions, 2007

Oscillatory behaviour of silicon electrodes in fluoride containing solution results in formation ... more Oscillatory behaviour of silicon electrodes in fluoride containing solution results in formation of nanoporous oxides. Metal electrodeposition into these pores results in local Schottky junction formation. Metal nanoemitters are contacted with a transparent conductive oxide and aluminum contact fingers for preparation of the first device (Al/ZnO/Pt-SiO 2 /Si/GaIn/Ag). Present solar-toelectrical conversion efficiencies are small and various improvement possibilities are outlined.

Research paper thumbnail of Interface condition of n-Si(111) during photocurrent oscillations in NH4F solutions

Journal of Electroanalytical Chemistry, 1995

ABSTRACT

Research paper thumbnail of Efficient photoelectrochemical nanoemitter solar cell

Electrochemistry Communications, 2008

Photoelectrochemical solar cells convert solar energy into electricity as fuels . The operation i... more Photoelectrochemical solar cells convert solar energy into electricity as fuels . The operation is based on the contact potential between a semiconductor and a redox electrolyte that results in the separation of photoinduced excess charge carriers. The applicability of photoelectrochemical solar energy conversion, however, is limited by photocorrosion at the reactive interface. Here, a new efficient photoelectrochemical solar cell is reported that avoids contact between semiconductor and electrolyte. The operational principle is based on metallic nanoemitters that form local contacts between the semiconductor absorber and the redox electrolyte while the remaining semiconductor surface is covered by an insulating anodic oxide. The nanoporous oxide, prepared by an oscillatory self-organised electrochemical process, serves as a template for spatially selective metal nanoemitter electrodeposition, resulting in a Si/SiO 2 /Pt nanocomposite structure after Pt deposition. In contact with I À =I À 3 redox electrolyte, a solar conversion efficiency of 11.2% has been obtained with the cell n À Si=SiO 2 =Pt=I À =I À 3 =C. The novel concept is characterized by the scalability of the employed oscillatory process, low-temperature processing, protection of the semiconductor surface from the solution and applicability in monolithically integrated solar fuel generating devices (photoelectrocatalysis) and solid-state solar cells.

Research paper thumbnail of Growth and characterization of ZnO thin films prepared by electrodeposition technique

Solar Energy Materials and Solar Cells, 2006

ZnO thin films were deposited on either indium tin oxide-coated glass or copper substrate by the ... more ZnO thin films were deposited on either indium tin oxide-coated glass or copper substrate by the electrodeposition process, using zinc chloride and flowing air as precursors. The effect of pH on the structural and morphological ZnO films was studied and the optimum deposition conditions have been outlined. The kinetics of the growth of the films have been investigated. We note that the rate of deposition of ZnO in an acidic solution was larger than in a basic solution. The structure of the films was studied using X-ray diffractometry (XRD) and transmission electron microscopy (TEM). The surface morphology and thickness of the films were determined using scanning electron microscopy. The X-ray diffraction analysis shows that the films are polycrystalline with hexagonal crystal structure (zincite) at pH 4. The optical transmittance of ZnO decreases with varying film thickness. The optical energy bandgap was found to be 3.26 eV.

Research paper thumbnail of Anodic preparation of porous TiO2 in fluoride solution

physica status solidi (c), 2005

Thick and homogeneous layers of porous TiO 2 (anatase and amorphous phases) have been prepared by... more Thick and homogeneous layers of porous TiO 2 (anatase and amorphous phases) have been prepared by anodization of Ti foils in fluoride solutions. The porous TiO 2 layers have been investigated by electron microscopy, Raman spectroscopy and photovoltage spectroscopy. The nanostructure of the porous TiO 2 layers depends sensitively on the pH and on the concentration of the NH 4 F solution. The photovoltage spectra of as-prepared samples are dominated by defects (electron traps) below the bandgap of anatase. The defects are removed after annealing in air.

Research paper thumbnail of Etch Rates of Anodic Silicon Oxides in Dilute Fluoride Solutions

Journal of The Electrochemical Society, 2003

ABSTRACT

Research paper thumbnail of High resolution surface analysis of Si roughening in dilute ammonium fluoride solution

Journal of Electroanalytical Chemistry, 2003

The initial stages of porous Si formation on Si(111) in dilute ammonium fluoride solution are ana... more The initial stages of porous Si formation on Si(111) in dilute ammonium fluoride solution are analysed by photoelectron spectroscopy using synchrotron radiation (SRPES). The PES results in the por-Si formation regime partly support a recent dissolution model. The contribution from the Si 2p surface core level shift shows that 0.35 ML of the surface is still H-terminated after interruption of the conditioning process at the first photocurrent maximum. Two signals shifted in binding energy by 0.8 and 1 eV, respectively, are attributed to reaction intermediates expected from the proposed reaction mechanism and from theoretical calculations using density functional theory (DFT). A distinct roughening is found in in-situ AFM measurements, with a calculated RMS roughness parameter of 2.6 nm. # 2002 Published by Elsevier Science B.V.

Research paper thumbnail of Electrochemical Method for Evaluation of Structural Perfection of Hydrogen-Terminated Si(111) Surface

Japanese Journal of Applied Physics, 2000

Abstract In this study, we measured the electrochemical oxidation currents on n-Si (111) surfaces... more Abstract In this study, we measured the electrochemical oxidation currents on n-Si (111) surfaces at a potential near the flat-band potential. The current became small when the surface was treated with oxygen-free water, which is effective for flattening the Si (111) ...

Research paper thumbnail of One, step electrodeposition of Cu(Ga,In)Se 2 thin films from aqueous solution

Journal de Physique IV (Proceedings), 2005

Cu(In,Ga)Se{2} (CIGS) semiconducting thin films films were prepared by electrodeposition from aqu... more Cu(In,Ga)Se{2} (CIGS) semiconducting thin films films were prepared by electrodeposition from aqueous solution containing CuCl{2}, InCl{3}, GaCl{3} and H{2}SeO{3}. The deposited material was characterized by cyclic voltammetry. The compositional, structural studies were carried out using scanning electron microscopy (SEM), energy dispersive X-ray microanalysis (EDX), X-ray diffraction (XRD) and transmission electron microscopy (TEM). X-ray analysis showed the formation of CuIn{1-x}GaxSe{2} films,

Research paper thumbnail of Photoactive nanostructure device by electrochemical processing of silicon

Journal of Electroanalytical Chemistry, 2008

The realization of a photoactive Si-based device that operates in the photovoltaic as well as in ... more The realization of a photoactive Si-based device that operates in the photovoltaic as well as in the photoelectrocatalytic mode is described. The system is based on self organized nanopore formation in the anodic silicon oxide which is present during current oscillations in fluoride containing electrolytes. Electrodeposition of Schottky barrier and/or catalytic metals into the pores forms nanoemitter contacts. In contact with redox electrolytes, comparably efficient photoelectrochemical solar energy conversion is obtained. With n-type Si, solar-to-electricity conversion efficiencies are between 6% and 7%. For illuminated p-Si, hydrogen evolution is observed. Present limitations in efficiencies are attributed to the non-optimized pore metallization process and reduced interface electronic quality for the photovoltaic system. For p-Si, the low contact potential difference between its Fermi level and the electrochemical potential for hydrogen evolution limits the attainable photovoltage. Routes for improvement of both devices are outlined.