Study of radio frequency plasma treatment of PVDF film using Ar, O2 and Ar + O2 gases for improved polypyrrole adhesion

Improvement of the binding of polypyrrole with PVDF (polyvinylidene fluoride) thin film using low pressure plasma was studied. The effects of various plasma gases i.e., Ar, O2 and Ar + O2 gases on surface roughness, surface chemistry and hydrophilicity were noted. The topographical change of the PVDF film was observed by means of scanning electron microscopy and chemical changes by X-ray photoelectron spectroscopy, with adhesion of polypyrrole (PPy) by abrasion tests and sheet resistance measurements. Results showed that the increase in roughness and surface functionalization by oxygen functional groups contributed to improved adhesion and Ar + O2 plasma gave better adhesion.

Thin and flexible solid-state organic ionic plastic crystal-polymer nanofibre composite electrolytes for device applications

All solid-state organic ionic plastic crystal–polymer nanofibre composite electrolytes are described for the first time. The new composite materials exhibit enhanced conductivity, excellent thermal, mechanical and electrochemical stability and allow the production of optically transparent, free-standing, flexible, thin film electrolytes (10’s lms thick) for application in electrochemical devices. Stable cycling of a lithium cell incorporating the new composite electrolyte is demonstrated, including cycling at lower temperatures than previously possible with the pure material.

A biocompatible ionic liquid as an antiwear additive for biodegradable lubricants

A biocompatible ionic liquid, tributyl(methyl)phosphonium diphenylphosphate, P1444DPP (IL1) was investigated as an antiwear additive and compared against Amine Phosphate (AP), one of the commonly used conventional antiwear additives in biodegradable lubricants. IL1 showed excellent antiwear performance, using a pin-on-disc tribometer, when blended in biodegradable base stocks. The steel balls after the test were analyzed using SEM-EDS techniques which confirmed the presence of phosphorous. The tribological properties under reciprocating conditions were also carried out using Optimol SRV oscillating friction and wear tester and the steel discs were observed under Atomic Force Microscopy (AFM), to show the buildup of tribofilm formed by IL1. The thickness of the lubricant film was confirmed by Elastohydrodynamic (EHD) Ultra Thin Film Measurement System. It was observed that IL1 has a better film forming ability than AP. © 2014 Elsevier Ltd.

Mechanical Behavior of Nano-crystalline Metallic Thin Films and Multilayers Under Microcompression

Microcompression tests were performed to determine the mechanical behavior of nano-crystalline Cu/Fe and Fe/Cu multilayers, as well as monolithic Cu and Fe thin films. The results show that the micropillars of pure Cu thin film bulge out under large compressive strains without failure, while those of pure Fe thin film crack near the top at low compressive strains followed by shear failure. For Cu/Fe and Fe/Cu multilayers, the Cu layers accommodate the majority of plastic deformation, and the geometry constraints imposed by Fe layers exaggerates the bulging in the Cu layers. However, the existence of ductile Cu layers does not improve the overall ductility of Cu/Fe and Fe/Cu multilayers. Cracking in the Fe layers directly lead to the failure of the multilayer micropillars, although the Cu layers have very good ductility. The results imply that suppressing the cracking of brittle layers is more important than simply adding ductile layers for improving the overall ductility of metallic multilayers.

Fabrication of meso-porous sintered metal thin films by selective etching of silica based sacrificial template

 Meso-porous metal materials have enhanced surface energies offering unique surface properties with potential applications in chemical catalysis, molecular sensing and selective separation. In this paper, commercial 20 nm diameter metal nano-particles, including silver and copper were blended with 7 nm silica nano-particles by shear mixing. The resulted powders were cold-sintered to form dense, hybrid thin films. The sacrificial silica template was then removed by selective etching in 12 wt% hydrofluoric acid solutions for 15 min to reveal a purely metallic meso-porous thin film material. The impact of the initial silica nano-particle diameter (7–20 nm) as well as the sintering pressure (5–20 ton·m−2) and etching conditions on the morphology and properties of the final nano-porous thin films were investigated by porometry, pyknometery, gas and liquid permeation and electron microscopy. Furthermore, the morphology of the pores and particle aggregation during shear mixing were assessed through cross-sectioning by focus ion beam milling. It is demonstrated that meso-pores ranging between 50 and 320 nm in average diameter and porosities up to 47% can be successfully formed for the range of materials tested.

Strain gradients in Cu-Fe thin films and multilayers during micropillar compression

Plastic strain gradients can influence the work-hardening behaviour of metals due to the accumulation of geometrically necessary discolations at the micron/submicron scale. A finite element model based on the conventional theory of mechanism-based strain-gradient plasticity has been developed to simulate the micropillar compression of Cu–Fe thin films and multilayers. The modelling results show that the geometric constraints lead to inhomogeneous deformation in the Cu layers, which agrees well with the bulging of Cu layers observed experimentally. Plastic strain gradients develop inside the individual layers, leading to extra work-hardening due to the accumulation of geometrically necessary dislocations. In the multilayer specimens, the Cu layers deform more severely than the Fe layers, resulting in the development of tensile stresses in the Fe layers. It is proposed that these tensile stresses are responsible for the development of micro-cracks in the Fe layers.

Filmes nanométricos de FeN e ALN crescidos por sputtering e aplicações do efeito peltier

This study will show the capability of the reactive/nonreactive sputtering (dc/rf) technique at low power for the growth of nanometric thin films from magnetic materials (FeN) and widegap semiconductors (AlN), as well as the technological application of the Peltier effect using commercial modules of bismuth telluride (Bi2Te3). Of great technological interest to the high-density magnetic recording industry, the FeN system represents one of the most important magnetic achievements; however, diversity of the phases formed makes it difficult to control its magnetic properties during production of devices. We investigated the variation in these properties using ferromagnetic resonance, MOKE and atomic force microscopy (AFM), as a function of nitrogen concentration in the reactive gas mixture. Aluminum nitride, a component of widegap semiconductors and of considerable interest to the electronic and optoelectronic industry, was grown on nanometric thin film for the first time, with good structural quality by non-reactive rf sputtering of a pure AlN target at low power (≈ 50W). Another finding in this study is that a long deposition time for this material may lead to film contamination by materials adsorbed into deposition chamber walls. Energy-dispersive X-ray (EDX) analysis shows that the presence of magnetic contaminants from previous depositions results in grown AlN semiconductor films exhibiting magnetoresistance with high resistivity. The Peltier effect applied to commercially available compact refrigeration cells, which are efficient for cooling small volumes, was used to manufacture a technologically innovative refrigerated mini wine cooler, for which a patent was duly registered

Characterization of metallic electrical contacts to SnO2 thin films lightly doped with Eu3+ ions, and photo-induced resistivity

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Kinetics of interface state-limited hole injection in alpha-naphthylphenylbiphenyl diamine (alpha-NPD) thin layers

Injection-limited operation is identified in thin-film, alpha-NPD-based diodes. A detailed model for the impedance of the injection process is provided which considers the kinetics of filling/releasing of interface states as the key factor behind the injection mechanism. The injection model is able to simultaneously account for the steady-state, current-voltage (J-V) characteristics and impedance response. and is based on the sequential injection of holes mediated by energetically distributed surface states at the metal-organic interface. The model takes into account the vacuum level offset caused by the interface dipole, along with the partial shift of the interface level distribution with bias voltage. This approach connects the low-frequency (similar to 1 Hz) capacitance spectra, which exhibits a transition between positive to negative values, to the change in the occupancy of interface states with voltage. Simulations based on the model allow to derive the density of interface states effectively intervening in the carrier injection (similar to 5 x 10(12) cm(-2)), which exhibit a Gaussian-like distribution. A kinetically determined hole barrier is calculated at levels located similar to 0.4 eV below the contact work function. (C) 2008 Elsevier B.V. All rights reserved.

Polymeric precursor method to the synthesis of XWO(4) (X = Ca and Sr) thin films-Structural, microstructural and spectroscopic investigations

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Improvement of electrical properties of Sr-modified (Pb,Ca)TiO3 thin films grown by soft chemistry route

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Ferroelectric and piezoelectric properties of bismuth layered thin films grown on (100) Pt electrodes

The effect of film orientation on piezoelectric and ferroelectric properties of bismuth layered compounds deposited on platinum coated silicon substrates was investigated. Piezo-force microscopy was used to probe the local piezoelectric properties of Bi(4)Ti(3)O(12), CaBi(4)Ti(4)O(15) and SrBi(4)Ti(4)O(15) films. Our measurements on individual grains clearly reveal that the local piezoelectric properties are determined by the polarization state of the grain. A piezoelectric coefficient of 65 pm/V was attained after poling in a grain with a polar axis very close to the normal direction. The piezoelectric coefficient and the remanent polarization were larger for a-b axes oriented than for c-axis-oriented films. (c) 2007 Elsevier B.V All rights reserved.

Investigation of nonlinear dielectric properties in Sr0.75Ba0.25Nb2O6 relaxor ferroelectric thin films

The ac and dc driving fields dependence of the dielectric permittivity for the strontium barium niobate relaxor ferroelectric thin films has been investigated. The nonlinear dielectric properties were obtained by using the measurements of the dielectric permittivity of the material as a function of the ac and dc "bias" electric field amplitude in wide frequency (100 Hz-10 MHz) and temperature (50-450 K) intervals. The results hint the existence of a true mesoscopic dielectric relaxor response in the ferroelectric thin film, which is very similar to those observed in bulk relaxor ferroelectrics. An anomalous behavior of the NL dielectric response was observed when submitted to moderate dc electric fields levels,,indicating a crossover from paraelectric to a glasslike behavior on cooling the sample toward the freezing transition. The obtained results were analyzed within the framework of the models proposed in the current literature.

Photocatalytic decomposition of diclofenac potassium using silver-modified TiO(2) thin films

The effects of silver insertion on the TiO(2) photocatalytic activity for the degradation of diclofenac potassium were reported here. Techniques such as X-ray diffraction, scanning electron microscopy and UV-Vis spectroscopy were used to comprehend the relation between structure and properties of the silver-modified TiO(2), thin films obtained by the sol-gel method. The lattice parameters and the crystallinity of TiO(2) anatase phase were affected by inserted silver, and the film thickness increased about 4 nm for each 1 wt.% of silver inserted. The degradation of diclofenac potassium and by-products reached an efficiency of 4.6 mg(C) W(-1) when the material was modified with silver. Although the first step of degradation involves only the photochemical process related to the loss of the chlorine and hydrogen atoms. This cyclization reaction leads to the formation of intermediate, which degradation is facilitated by the modified material. (C) 2007 Elsevier B.V. All rights reserved.