Showing papers by "Igor Luzinov published in 2009"

Capillary and surface effects in the formation of nanosharp tungsten tips by electropolishing.

Abstract: The DC electropolishing process has been applied to the sharpening of tungsten wires in 2 M KOH aqueous solution. Necking of tungsten anodes takes place in the vicinity of the electrolyte−air interface. This results in the creation of two separate wire parts with nanosharp tips. Using image analysis, we demonstrate that the products of electrochemical reactions on the wire surface form a film with distinguishable properties. Experimental estimates of the film density and interfacial tension show that the film is approximately 32 kg/m3 denser than the surrounding electrolyte and that its interfacial tension is approximately σ ≈ 0.2 mN/m. Using these estimates, we show that the film flow is predominantly driven by capillary forces. We hypothesize that the wire necking is caused by a bidirectional film flow originated from Plateau−Rayleigh instability and inherent to cylindrical films and jets.

Electrical Characterization of Tantalum Capacitors with Poly(3,4-ethylenedioxythiophene) Counter Electrodes

Abstract: A combination of structural and electrical characterization techniques was applied to polymer Ta capacitors with in situ and prepolymerized poly(3,4-ethylenedioxythiophene) (PEDOT) cathodes with a broad range of Ta 2 O 5 dielectric thicknesses. The in situ PEDOT was produced by polymerizing the EDOT monomer using an oxidizer/dopant. The prepolymerized material was an aqueous suspension of doped polymer which was dried to produce the PEDOT film. Experimental data show that polymer Ta capacitors with prepolymerized PEDOT have lower dc leakage and higher breakdown voltage (BDV) compared to polymer Ta capacitors with in situ PEDOT. The difference in dc leakage and BDV between these two types of capacitors becomes greater with increasing thickness and improved structure of the Ta 2 O 5 dielectric film. These experimental results are inconsistent with current theories presented in the literature. An alternative model is presented based on classical metal/insulator/semiconductor (MIS) theory, where in this case M corresponds to the Ta metal, I corresponds to the Ta 2 O 5 insulator, and S corresponds to the semiconducting PEDOT. According to this model, a potential barrier for the current carriers at the insulator/semiconductor interface controls the current flow through the Ta 2 O 5 dielectric under normal operating conditions (positive polarity on the Ta anode and a temperature range of ―55°C ≤ T ≤ 105°C). In situ polymerization of the PEDOT adversely affects this barrier, while the prepolymerized PEDOT suspension leaves it essentially intact. The different migratory ability of the dopants in in situ and prepolymerized PEDOT also contributes to the differences in electrical performance of polymer Ta capacitors with in situ and prepolymerized PEDOT cathodes.

Toward protein imprinting with polymer brushes

Abstract: The authors described an original approach for a surface protein imprinting employing grafting of polymer brushes. Protein molecules were first chemically bound to an ultrathin (1–3 nm) poly(glycidyl methacrylate) reactive polymer layer and later removed by protease treatment. Residual amino acids became grafted to the surface and to a certain extent imitated the surface chemical composition and shape of the template molecule on a nanolevel. The space surrounding the adsorbed biomolecules was modified with grafted poly(ethylene glycol) layer. This led to the formation of islands of spatial nanosized pockets complementary to the protein shape. The adsorbing protein recognized the surfaces imprinted and was anchored to the substrate.

Gluing nanoparticles with a polymer bonding layer: the strength of an adhesive bond.

Abstract: The adhesive joint between silica nanoparticles and ultrathin poly(vinylpyridine) (PVP) layers (thickness between 3 and 100 nm) was tested using the cantilever of an atomic force microscope. Specifically, the strength of the adhesive bond (or practical adhesion) was probed in a tearing contact mode, when the particle was removed by applying a tangential force parallel to the substrate surface. The effect of the polymer molecular weight and layer thickness on the particle (practical) adhesion was investigated. It was found that the particles were removed by destroying the cohesive contact zone and that the PVP layer thickness had a pronounced effect on the force needed to destroy the adhesive joint. In particular, the greater the layer thickness, the larger was the required break force. However, the strength of the adhesive joint was estimated to be higher for a thinner layer. It is suggested that mechanical properties of the system as well as molecular characteristics of the PVP layer are responsible for ...

Progress on the Fabrication of On-Chip, Integrated Chalcogenide Glass (ChG)-Based Sensors

Abstract: Optical sensor technologies for chemical detection have advanced over the past decade. We report progress on the material design, fabrication and performance of high-Q chalcogenide glass resonators utilizing cavity-enhancement for high sensitivity MIR chemical sensing.

Development of novel integrated bio/chemical sensor systems using chalcogenide glass materials

Abstract: This paper reviews ongoing progress in the design and fabrication of new, on-chip, low loss planar molecular sensors. We report the details of device design, material selection and manufacturing processes used to realise high-index-contrast (HIC), compact micro-disk resonators. These structures have been fabricated in thermally evaporated As- and Ge-based chalcogenide glass films with PDMS (polydimethylsiloxane) micro-fluidic channels using standard UV lithography. Discussed are findings that demonstrate that our novel chalcogenide-based micro-fluidic device can be used as highly sensitive refractive index sensors.

Coatings via Self-Assembly of Smart Nanoparticles

Abstract: The present communication focuses on a novel method for the fabrication of smart coatings based on colloidal systems that combine nanoparticles and spherical responsive polymer brushes. The motivation for this work relies on the traditional and successful applications of composite coatings produced from a polymer matrix and inorganic particles. New properties of such hybrid systems can be approached by the precise design of the dimensions, structure and functionality of the building blocks.