Interface and surface analysis of Ru/CdS
01 Jan 1996-Journal of Materials Science Letters (Kluwer Academic Publishers)-Vol. 15, Iss: 21, pp 1921-1923
About: This article is published in Journal of Materials Science Letters.The article was published on 1996-01-01. It has received 4 citations till now.
Citations
More filters
TL;DR: For a variety of metals and semiconductors, an attempt is made to generalize observations in the literature on the effect of process conditions applied during photodeposition on (i) particle size distributions, (ii) oxidation states of the metals obtained, and (iii) consequences for photocatalytic activities.
Abstract: In this review, for a variety of metals and semiconductors, an attempt is made to generalize observations in the literature on the effect of process conditions applied during photodeposition on (i) particle size distributions, (ii) oxidation states of the metals obtained, and (iii) consequences for photocatalytic activities. Process parameters include presence or absence of (organic) sacrificial agents, applied pH, presence or absence of an air/inert atmosphere, metal precursor type and concentration, and temperature. Most intensively reviewed are studies concerning (i) TiO2; (ii) ZnO, focusing on Ag deposition; (iii) WO3, with a strong emphasis on the photodeposition of Pt; and (iv) CdS, again with a focus on deposition of Pt. Furthermore, a detailed overview is given of achievements in structure-directed photodeposition, which could ultimately be employed to obtain highly effective photocatalytic materials. Finally, we provide suggestions for improvements in description of the photodeposition methods applied when included in scientific papers.
648 citations
TL;DR: It is demonstrated further that a fine control of the metal Ru nanoparticle size on the TiO2 support was possible via a controlled nanocluster growth under irradiation, while the nanoparticles revealed a good resistance to thermal sintering.
Abstract: Ru/TiO₂ are promising heterogeneous catalysts in different key-reactions taking place in the catalytic conversion of biomass towards fuel additives, biofuels, or biochemicals. TiO₂ supported highly dispersed nanometric-size metallic Ru catalysts were prepared at room temperature via a solar light induced photon-assisted one-step synthesis in liquid phase, far smaller Ru nanoparticles with sharper size distribution being synthesized when compared to the catalysts that were prepared by impregnation with thermal reduction in hydrogen. The underlying strategy is based on the redox photoactivity of the TiO₂ semi-conductor support under solar light for allowing the reduction of metal ions pre-adsorbed at the host surface by photogenerated electrons from the conduction band of the semi-conductor in order to get a fine control in terms of size distribution and dispersion, with no need of chemical reductant, final thermal treatment, or external hydrogen. Whether acetylacetonate or chloride was used as precursor, 0.6 nm sub-nanometric metallic Ru particles were synthesized on TiO₂ with a sharp size distribution at a low loading of 0.5 wt.%. Using the chloride precursor was necessary for preparing Ru/TiO₂ catalysts with a 0.8 nm sub-nanometric mean particle size at 5 wt.% loading, achieved in basic conditions for benefitting from the enhanced adsorption between the positively-charged chloro-complexes and the negatively-charged TiO₂ surface. Remarkably, within the 0.5⁻5 wt.% range, the Ru content had only a slight influence on the sub-nanometric particle size distribution, thanks to the implementation of suitable photo-assisted synthesis conditions. We demonstrated further that a fine control of the metal Ru nanoparticle size on the TiO₂ support was possible via a controlled nanocluster growth under irradiation, while the nanoparticles revealed a good resistance to thermal sintering.
11 citations
TL;DR: In this paper, the effect of the variation of the incident irradiance and photodeposition rate on the photocatalytic properties of ruthenium nanoparticles supported on TiO2 was evaluated by using the degradation of formic acid in water under UV-A light.
Abstract: Photoassisted synthesis is as a highly appealing green procedure for controlled decoration of semiconductor catalysts with co-catalyst nanoparticles, which can be carried out without the concourse of elevated temperatures, external chemical reducing agents or applied bias potential and in a simple slurry reactor. The aim of this study is to evaluate the control that such a photoassisted method can exert on the properties of ruthenium nanoparticles supported on TiO2 by means of the variation of the incident irradiance and hence of the photodeposition rate. For that purpose, different Ru/TiO2 systems with the same metal load have been prepared under varying irradiance and characterized by means of elemental analysis, transmission electron microscopy and X-ray photoelectron spectroscopy. The photocatalytic activity of the so-obtained materials has been evaluated by using the degradation of formic acid in water under UV-A light. Particles with size around or below one nanometer were obtained, depending on the irradiance employed in the synthesis, with narrow size distribution and homogeneous dispersion over the titania support. The relation between neutral and positive oxidation states of ruthenium could also be controlled by the variation of the irradiance. The obtained photocatalytic activities for formic acid oxidation were in all cases higher than that of undecorated titania, with the sample obtained with the lowest irradiation giving rise to the highest oxidation rate. According to the catalysts characterization, photocatalytic activity is influenced by both Ru size and Ru0/Ruδ+ ratio.
1 citations
TL;DR: In this article, the changes in RuCl 3 formation and surface roughness with various cleaning processes were investigated and it was confirmed that, during Cl 2 dry etching to remove the absorber layer, RuCl3 was formed on the Ru capping layer surface, and the surface roughs thereby deteriorated.
Abstract: Ru-capped extreme ultraviolet lithography photomasks require cleaning after patterning of the absorber layer. In this study, it was confirmed that, during Cl 2 dry etching to remove the absorber layer, RuCl 3 was formed on the Ru capping layer surface, and the surface roughness thereby deteriorated. Therefore, the changes in RuCl 3 formation and surface roughness with various cleaning processes were investigated. Among the treatments used, i . e ., sulfuric peroxide mixture, an ammonia peroxide mixture or ozonated water (DIO 3 ), DIO 3 exhibited the most effective Cl removal efficiency and surface roughness recovery. DIO 3 treatment successfully reduced the Cl-terminated Ru surface to its original state and decreased the surface roughness to the pre-Cl 2 -etched Ru value.
References
More filters
TL;DR: In this article, the chemical composition of sprayed CdS films has been evaluated using X-ray photoelectron spectroscopy and a definite correlation is observed between composition and process parameters.
Abstract: The chemical composition of sprayed CdS films has been evaluated using X-ray photoelectron spectroscopy. The general impurity content in the film is discussed, throwing light on the pyrolysis reaction involved in CdS deposition. Further, the stoichiometry of these films is studied as a function of process parameters such as pyrolysis temperature, Cd/S ratio in the solution, deposition rate and film thickness. A definite correlation is observed between composition and process parameters. The compositional variation appears to be related to the structure of CdS films as well as the growth mechanism. The effects induced by annealing in nitrogen, hydrogen and ambient air are also discussed. Hydrogen and nitrogen annealing is responsible for oxygen desorption from CdS. On the other hand air annealing induces stoichiometric variations along with oxygen intake in the films.
16 citations
TL;DR: In this article, the initial steps of Bi deposition are interpreted in terms of a nucleation and growth model based on progressive nucleation with diffusion-controlled transfer of Bi3+ at three-dimensional growth centres.
Abstract: The electrolytic deposition of Bi on CdS(0001) single-crystal surfaces has been studied in aqueous 0.5 M NaClO4 + x M Bi(ClO4)3 solutions (pH 2) using electrochemical dc and pulse polarization techniques under potentiostatic control. The initial steps of Bi deposition are interpreted in terms of a nucleation and growth model based on progressive nucleation with diffusion-controlled transfer of Bi3+ at three-dimensional growth centres. The number-density and mean size of the Bi crystallites are determined as a function of the amount of Bi deposited. The formation of a localized Schottky barrier at the interface between the Bi crystallites and the CdS surface was found to prevent the anodic dissolution of the Bi deposit even at high anodic polarization in the dark as well as under illumination of the electrode surface. The deposition of Bi inhibits the photoanodic dissolution owing to geometrical blocking of the CdS surface by Bi crystallites.
11 citations
TL;DR: Ramakrishnan et al. as discussed by the authors used X-ray photoelectron spectroscopy (XPS) to probe the surface of materials and obtained a detailed surface study of Pd/CdS.
Abstract: I. B. RUFUS*,V. RAMAKRISHNAN, B. VISWANATHAN, J. C. KURIACOSE Department of Chemistry, Indian Institute of Technology, Madras 600036, India Metallized CdS is used as a photocatalyst for many reactions and as a photoanode in photoelectrochem- ical (PEC) cells [1-4]. Conversion and storage of solar energy can be achieved by means of photocata- lysis as well as by PEC cells. The photocatalytic and photoelectrochemical properties of metallized CdS depend on its surface properties. Pd/CdS is a better photocatalyst and photoanode than CdS [3]. However, a detailed surface study of Pd/CdS is lacking. X-ray photoelectron spectroscopy (XPS) is a versatile tool to probe the surface of materials. XPS investigation of Pd/CdS will yield useful infor- mation such as the oxidation state of Pd, the contact between Pd and CdS, and other species present on the surface. Metallized CdS is mostly prepared by the photodeposition of noble metals [1, 3, 4]. There- fore, in the present investigation Pd, one of the representatives of noble metals, was photodeposited on CdS and the Pd/CdS obtained was analysed by XPS. Pd, Pt, Rh, Ru and Ni/CdS were prepared by the simultaneous photodeposition (illuminating for 15 min with a 1000 W tungsten-halogen lamp) of these metals on a sintered (4 h at 873 K in nitrogen) CdS (Fluka, 99.999% purity) pellet from an equi- molar (1 x 10 -4 M) solution (acetic acid, pH 4.5) of the corresponding metal chlorides. Following a similar procedure, Pd was photodeposited from a solution of PdC12 (Arora Mathey Ltd, India). After photodeposition the pellets were washed with triply distilled water and dried in air at room temperature (303 K). The sides of the pellets that were exposed to visible light during the photodeposition were subjected to XPS analysis. The XPS studies were made with an ESCA Lab Mk II (VG Scientific Co., UK) at room temperature and at a pressure of 1 x 10 -7 Pa before and after sputtering with argon ions. The X-ray source used was MgKo~ with an energy of 1253.6 eV. The C ls peak at 285.0 eV was used as the internal standard. In the cases of Pd, Pt, Rh, Ru and Ni/CdS prepared by the simultaneous photodeposition of these metals, the Pd 3d and 3p binding energies (Figs 1 and 2) are higher than those reported for Pd metal, viz. 344.7, 340.0 and 531.5 eV [5], indicating that Pd which is on the surface of CdS is not in the zero oxidation state. The several Pd-O species identified are shown in Table I. Hence, in the case of Pd/CdS the XPS spectra were recorded only after argon-ion sputtering, in order to study the surface free of oxide
8 citations
01 Jan 1993
TL;DR: Ramakrishnan et al. as discussed by the authors used X-ray photoelectron spectroscopy (XPS) to probe the surface of materials and obtained a detailed surface study of Pd/CdS.
Abstract: I. B. RUFUS*,V. RAMAKRISHNAN, B. VISWANATHAN, J. C. KURIACOSE Department of Chemistry, Indian Institute of Technology, Madras 600036, India Metallized CdS is used as a photocatalyst for many reactions and as a photoanode in photoelectrochem- ical (PEC) cells [1-4]. Conversion and storage of solar energy can be achieved by means of photocata- lysis as well as by PEC cells. The photocatalytic and photoelectrochemical properties of metallized CdS depend on its surface properties. Pd/CdS is a better photocatalyst and photoanode than CdS [3]. However, a detailed surface study of Pd/CdS is lacking. X-ray photoelectron spectroscopy (XPS) is a versatile tool to probe the surface of materials. XPS investigation of Pd/CdS will yield useful infor- mation such as the oxidation state of Pd, the contact between Pd and CdS, and other species present on the surface. Metallized CdS is mostly prepared by the photodeposition of noble metals [1, 3, 4]. There- fore, in the present investigation Pd, one of the representatives of noble metals, was photodeposited on CdS and the Pd/CdS obtained was analysed by XPS. Pd, Pt, Rh, Ru and Ni/CdS were prepared by the simultaneous photodeposition (illuminating for 15 min with a 1000 W tungsten-halogen lamp) of these metals on a sintered (4 h at 873 K in nitrogen) CdS (Fluka, 99.999% purity) pellet from an equi- molar (1 x 10 -4 M) solution (acetic acid, pH 4.5) of the corresponding metal chlorides. Following a similar procedure, Pd was photodeposited from a solution of PdC12 (Arora Mathey Ltd, India). After photodeposition the pellets were washed with triply distilled water and dried in air at room temperature (303 K). The sides of the pellets that were exposed to visible light during the photodeposition were subjected to XPS analysis. The XPS studies were made with an ESCA Lab Mk II (VG Scientific Co., UK) at room temperature and at a pressure of 1 x 10 -7 Pa before and after sputtering with argon ions. The X-ray source used was MgKo~ with an energy of 1253.6 eV. The C ls peak at 285.0 eV was used as the internal standard. In the cases of Pd, Pt, Rh, Ru and Ni/CdS prepared by the simultaneous photodeposition of these metals, the Pd 3d and 3p binding energies (Figs 1 and 2) are higher than those reported for Pd metal, viz. 344.7, 340.0 and 531.5 eV [5], indicating that Pd which is on the surface of CdS is not in the zero oxidation state. The several Pd-O species identified are shown in Table I. Hence, in the case of Pd/CdS the XPS spectra were recorded only after argon-ion sputtering, in order to study the surface free of oxide
7 citations
4 citations