Search results for "thin film"
showing 10 items of 1200 documents
Ruthenium pentamethylcyclopentadienyl mesitylene dimer: a sublimable n-dopant and electron buffer layer for efficient n-i-p perovskite solar cells
2019
Electron-transport materials such as fullerenes are widely used in perovskite solar cells to selectively transfer the photogenerated electrons to the electrodes. In order to minimize losses at the interface between the fullerene and the electrode, it is important to reduce the energy difference between the transport level of the two materials. A common approach to reduce such energy mismatch is to increase the charge carrier density in the semiconductor through doping. A variety of molecular dopants have been reported to reduce (n-dope) fullerenes. However, most of them are either difficult to process or extremely air sensitive, with most n-dopants leading to the formation of undesirable si…
Second-layer induced island morphologies in thin-film growth of fullerenes.
2011
Deposition of fullerenes on the CaF(2)(111) surface yields peculiar island morphologies with close similarities to previous findings for (100) surfaces of other ionic crystals. By means of noncontact atomic force microscopy we find a smooth transition from compact, triangular islands to branched hexagonal islands upon lowering the temperature. While triangular islands are two monolayers high, hexagonal islands have a base of one monolayer and exhibit a complicated structure with a second-layer outer rim and trenches oriented towards the interior. By developing a kinetic growth model we unravel the microscopic mechanisms of the structure formation.
Atmosphere-induced change of microhardness and plasticity of C60 single crystals and polycrystalline films
1998
Abstract The effect of air exposure and visible light illumination on the microhardness, plasticity and dislocation mobility in the C60 single crystals was investigated. Microhardness values for defined structural states of the fullerene (pristine, oxygen-intercalated, photo-oxidized) are reported. It has been shown that oxygen intercalation in the fullerene lattice during air-aging in the dark results in the suppression of dislocation mobility. However, only a slight increase in the hardness of oxygenated samples was observed. A remarkable increase in the hardness and decrease in the plasticity of the C60 crystals under illumination-assisted air exposure was noted. Photochemical transforma…
Bending Sensors Based on Thin Films of Semitransparent Bithiophene-Fulleropyrrolidine Bisadducts
2020
In this study, a novel bithiophene‐fulleropyrrolidine bisadducts system (bis‐Th2PC 60 ) was synthesized and electropolymerized by chronoamperometry onto flexible ITO/PET substrates. The resulting semitransparent thin film was characterized by XPS, FT‐IR, cyclic voltammetry and optical techniques, confirming the good outcome of the electropolymerization process. AFM investigations permitted to highlight an inherent disordered granular morphology, in which the grain‐to‐grain separation depends upon the application of bending. The electrical resistance of the thin film was characterized as function of bending (in the range 0°‐90°), showing promising responsivity to low bending angles (10°‐30°)…
In-situ electrochemical atomic force microscopy study of aging of magnetron sputtered Pt-Co nanoalloy thin films during accelerated degradation test
2016
Abstract A Pt-Co nanoalloy thin film catalyst was prepared by using simultaneous magnetron sputtering of Pt and Co. The catalyst was characterized during accelerated degradation test using in-situ electrochemical atomic force microscopy complemented with ex-situ techniques such as energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and synchrotron radiation photoelectron spectroscopy. The combined results gave the full step-by-step picture of the catalyst behavior during the aging test.
Synthesis of a New Copper-Azobenzene Dicarboxylate Framework in the Form of Hierarchical Bulk Solids and Thin Films without and with Patterning
2011
Reaction of copper(II) acetate with azobenzene-4,4′-dicarboxylic acid results in the formation of a metal–organic framework with the unexpected stoichiometry of Cu(II):ligand of 2:1. The bulk synthesis results in microspheres assembled from either nanobricks or nanoflakes, depending on the ratio of the reactants in solution. While the former behaves like a bulk solid with clear reflections in the X-ray and electron diffraction experiments, the latter obviously is dominated by surface effects, with a significant fraction of slightly expanded elemental cells and a significantly increased outer surface area. The material could also be deposited on a variety of surfaces using a stepwise layer-b…
Modeling bimetallic corrosion under thin electrolyte films
2011
A finite element model (FEM) was developed to calculate the potential distribution in the electrolyte in the case of bimetallic corrosion between iron and zinc electrodes, taking into account mass transport of oxygen in the solution. This model was first compared with experimental results obtained by scanning vibrating electrode technique (SVET) on a galvanized steel cut-edge in immersion conditions in a 0.03 M NaCl electrolyte. A good agreement was obtained between the calculated and experimental current densities. The model predicted the evolution of the galvanic coupling as function of the electrolyte thickness and for various iron–zinc surface area ratios. Different coupling regimes wer…
Viscoelastic potential-induced changes in acoustically thin films explored by quartz crystal microbalance with motional resistance monitoring
2015
Abstract Viscoelastic properties of intrinsically conducting polymers depend on different factors, among them polymer structure, ionic and solvent population and film thickness. During a voltammetric cycle, electrochemical reactions involve changes of these factors. Consequently, the viscoelastic properties are expected to be changed. Electrochemical quartz crystal microbalance with motional resistance monitoring were employed to calculate the instantaneous resonant frequency/motional resistance ratio (d f r / d R m ) during the electrochemical processes of acoustically thin films of poly(o-toluidine). d f r / d R m is defined as the energy dissipation factor and shows values around ∼10 Hz …
Integrated Cleanroom Process for the Vapor-Phase Deposition of Large-Area Zeolitic Imidazolate Framework Thin Films
2019
Chemistry of materials XX(XX), acs.chemmater.9b03435 (2019). doi:10.1021/acs.chemmater.9b03435
Molecular flattening effect to enhance the conductivity of fused porphyrin tape thin films.
2019
The straightforward synthesis of directly fused porphyrins (porphyrin tapes) from 5,15-diphenyl porphyrinato nickel(II) complexes with different substituents on the phenyl rings is achieved while processing from the gas phase. The porphyrin tapes, exhibiting NIR absorption, are readily obtained in thin film form. The gas phase approach cuts the need for solubilizing groups allowing for the first time the study of their conductivity according to the substituent. 2-Point probe and conductivity AFM measurements evidence that reducing the size of the meso substituents, phenyl < mesityl < di(3,5-tert-butyl)phenyl < di(2,6-dodecyloxy)phenyl, improves the thin film conductivity by several orders o…