Electro-chemical deposition of zinc oxide nanostructures by using two electrodes

One of the most viable ways to grow nanostructures is electro deposition. However, most electrodeposited samples are obtained by three-electrode electrochemical cell. We successfully use a much simpler two-electrode cell to grow different ZnO nanostructures from common chemical reagents. Concentration, pH of the electrolytes and growth parameters like potentials at the electrodes, are tailored to allow fast growth without complexity. Morphology and surface roughness are investigated by Scanning Electron and Air Force Microscopy (SEM and AFM) respectively, crystal structure by X-Ray Diffraction measurements (XRD) and ZnO stoichiometry by core level photoemission spectroscopy (XPS)

review of 2h tetraphenylporphyrins metalation in ultra high vacuum on metal surfaces

The formation and conformational adaptation of self-assembled monolayer of 2H- tetraphenylporphyrins (2H-TPPs) on metal surfaces, as well as their metalation processes in ultra-high vacuum (UHV), are reviewed. By means of XPS, NEXAFS and STM measurements we demonstrate that, after the annealing at 550 K, a temperature-induced chemical modification of 2H-TPP monolayer on Ag(111) occurs, resulting in the rotation of the phenyl rings parallel to the substrate plane. Moreover, independently of the conformation, we report three dierent methods to metalate 2H-TPP monolayers in UHV. Experimental evidence indicates that the presence of a metal atom in the TPP macrocycle influences both the conformation of the molecule and its adsorption distance

Growth and some surface characterization of tin Sulphide (SnS) thin film by two-electrode cell arrangement for photo absorption

This study presented deposition of tin sulphide (SnS) thin film using a two-electrode electrochemical cell arrangement. The bath electrolyte comprised tin sulphate (SnSO4 ), hydrated sodium thiosulphate (Na2S2O3∙5H2O) and sulphuric acid (H2SO4 ). The acid was used to adjust the pH of the bath. The deposited film was characterised using Surface Profilometer, X-Ray Diffractometer (XRD), Uv-Visible Spectrophotometer and four point probe technique. Surface profiling revealed that the film is continuous with thickness of about 60 nm. The XRD result showed that the film has orthorhombic crystal structure. Film's crystallite size was estimated as 0.61 nm and interplanar spacing as 0.29 nm. The Uv-visible Spectrophotometer result reveals that, the film has good absorbance but poor reflectance and transmittance in the visible light region. The film has direct allowed transition with energy band gap of 1.69 eV. Values of surface resistivity and conductivity were deduced from data obtained from Four-point probe studies as 5.12 x 10-4Ω-cm and 1.96 x 103Ω-1cm-1 respectively. The I-V characteristics curve of ITO/SnS/Ag structure is linear indicating an Ohmic contact between the substrate electrode and the deposited layer. It can therefore be suggested that the film can allow pathway for photoabsorption and also aid charge transfer in photovoltaic process. Keywords: tin sulphide, orthorhombic, electrochemical deposition, characterization, photovoltaic and surface resistivity

Preparation of nanocrystalline ZnO/CoxOyand CNT/CoxOybilayers for photoabsorption potential: XPS and some surface structural characterization

Zinc oxide and carbon nanotubes (CNT) have been separately grown atop cobalt oxide (CoxOy) thin film to form bilayer structures. The structures were characterized by some surface probing techniques. Surface morphology shows that particles of the underlying CoxOy film are evenly distributed across substrate, its average size increases between 60 and 73 nm with deposition voltage. A transparent layer of ZnO completely laminated the CoxOy film in the first set of bilayer sample. Thickness of overgrown CNT on CoxOy is about 16 nm. Dispersion of CoxOy crystallites along the path of the adsorbed CNT was also observed. Optical studies indicated that both the CoxOy film and the ZnO/CoxOy bilayers are fairly transparent to visible light. Values of their energy band gap were estimated in the range between 2.0 and 2.14 eV. Photoemission and crystallographic studies revealed possible interaction between particles of CoxOy and ZnO films but not with the substrate. The study suggests that both the laminated II-VI bilayer and the CNT enhanced structures could be a recipe for effective charge harvesting and separation in nanostructured photovoltaic device

Spray Pyrolysis Deposition and Characterisation of Dielectric SnO2 Thin Films

Dielectric and optical dispersion properties of thin films of SnO2 deposited via spray pyrolysis were investigated. These properties are fundamental to new applications of SnO2 in energy storage and pressure sensing. The composition and thickness of the films were determined using the Rutherford Backscattered Spectroscopic mode of the Pelletron Tandem Accelerator. X-ray diffraction (XRD) technique and scanning electron microscope (SEM) were used to examine the crystal structure and surface morphology of the films. Optical transmission data were analyzed to obtain the optical band gap, dispersion parameters, and dielectric constants. The analyses showed that the films were polycrystalline in nature with the tetragonal rutile crystal structure. It was also observed that annealed films increased in thickness compared to the asdeposited samples. The Urbach tail width of the annealed sample also decresed from 293 to 252 meV indicating an improvement in crystallinity with heat treatment. The refractive index dispersion in the visible region analyzed in terms of long wavelength single-oscillator Sellmier approximation was in the range 1.9 -3.0. The zero and high-frequency dielectric constants were evaluated. The values of these constants could be a justification for further exploration of SnO2-based materials for charge storage and capacitive pressure sensing. Keywords: pyrolysis, dielectric, refractive index, thin film