Ordered arrays of nanometer-sized optical probes with electrochemiluminescent properties were developed on the distal face of imaging fiber bundles. The fabrication steps are adapted from SNOM probes and nanoelectrodes methodologies and allow to produce high-density arrays of opto-electrochemical probes which retain the initial architecture of the bundle. Apertureless probe arrays and also nanoaperture arrays have thus been prepared. The angular distribution of the far-field intensity transmitted through such nanostructured arrays depends both on their respective architectures and on the characteristic dimensions of the nanoprobes. The subwavelength aperture arrays show a diffracting behavior which is a function of the optical aperture size. The far-field analysis demonstrates their potential application as a parallel near-field optical array in both apertureless and aperture configurations. In addition, each optical nanoaperture is surrounded by a ring-shaped gold nanoelectrode. The electrochemical response of the array is sigmoidal in shape indicating that the nanoelectrodes forming the array are diffusively independent. In other words, each nanoelectrode of the array probes electrochemically a different micro-environment. We show also that the nanoaperture array can be used as an electrochemiluminescent nanosensor array for NADH. Eventually, the arrays keep the imaging properties at both nanometer and micrometer scales. Indeed, each nanoprobe can explore optically a near-field region, whereas the global array allows imaging simultaneously a large micrometric area. This optical array format plays therefore a bridging role by interrelating optical and electrochemiluminescent information obtained concomitantly at the nanometer and micrometer scales.

Epitaxial heterostructures constitute a wide variety of modern microelectronics devices. In the limit of ever decreasing feature dimensions, now entering the nanoscale in some cases, the interfaces of such devices are crucial to their operation and performance. In general the properties of the interfaces will differ significantly from those of the bulk structure of either the substrate or the heteroepitaxial film. To date, direct, non-destructive characterizations of the atomic-level structure of films and interfaces have not been readily available and this has hampered the design and optimization of heteroepitaxial devices. We describe here a novel x-ray interference method which is useful for imaging such structures with sub-Ångstrom spatial resolution while also providing chemical composition information from a map of the electron density. We illustrate the method, known as Coherent Bragg Rod Analysis (COBRA), with recent results on GaSb-InAs heterostructures of interest as infrared sources and detectors. We show that, with detailed knowledge of the interfaces from COBRA, it is now feasible to correlate specific molecular beam epitaxy growth conditions with desired electronic characteristics associated with the interface bonding. The COBRA method is quite general and only requires an epitaxial relationship between the substrate and the nanostructure that is deposited on it.

Ultrafine tin oxide (SnO₂) fibers in the rutile structure, with diameters ranging from 60nm to several microns, were synthesized using electrospinning and metallorganic decomposition techniques. In this work we use a precursor solution which is a mixture of a pure SnO₂ sol made from SnCl₄ : H₂O : C₃H₇OH : 2-C₃H₇OH at a molar ratio of 1:9:9:6, and a viscous solution made from poly(ethylene oxide) (PEO) (molecular weight 900,000) and chloroform CHCl₃ at a ratio of 200mg PEO/10mL CHCl₃. This solution allows obtaining an appropriate viscosity for the electrospinning process. The as deposited fibers were sintered at 400, 500, 600, 700 and 800°C in air for two hours. Previous results using this method and characterizing the fibers with scanning electron microscopy (SEM), x-ray diffraction (XRD), Raman microspectrometry and x-ray photoelectron spectroscopy (XPS) showed that up to the sintering temperature of 700°C, the synthesized fibers are composed of SnO₂. Further analysis using SEM, Profilometry, Atomic Force Microscopy (SPM), Auger Spectroscopy and I/V analysis is presented in this paper. The results show that the fibers are composed of tin oxide and that smooth and continuous fibers in different shapes (straight, curved, ribbon-like, and spring-like) can be obtained using this method. The change in resistivity as a function of the annealing temperature can be attributed to the thermally activated formation of a nearly stoichoimetric solid.

We present a controlled, well-defined pattern replication of a micrometer template driven by a surface free energy lithographic technique, realized by molecular aggregation in dewetting conditions and by confining the liquid solution with geometric boundaries. The presented technique has allowed the fabrication of light-emitting devices, and in particular the realization of OLEDs with an array of addressable pixels.

Here we report the first demonstrations of infrared focal plane array (FPA) based on GaAs and InP based quantum dot infrared photodetectors (QDIPs). QDIPs are extension of quantum well infrared photodetectors (QWIPs) and are predicted to outperform QWIPs due to their potential advantages including normally incident absorption, higher responsivity and high temperature operation. Two material systems have been studied: InGaAs/InGaP QDIPs on GaAs substrates and InAs QDIP on InP substrates. An InGaAs/InGaP QDIP has been grown on GaAs substrate by LP-MOCVD. Photoresponse was observed at temperatures up to 200 K with a peak wavelength of 4.7 μm and cutoff wavelength of 5.2 μm. A detectivity of 1.2x10¹¹ cmHz^1/2/W was obtained at T=77 K and bias of -0.9 V, which is the highest for QDIPs grown by MOCVD. An InAs QDIP structure has also been grown on InP substrate by LP-MOCVD. Photoresponse of normal incidence was observed at temperature up to 160K with a peak wavelength of 6.4 μm and cutoff wavelength of 6.6 μm. A detectivity of 1.0x10¹⁰ cmHz^1/2/W was obtained at 77K at biases of -1.1 V, which is the first and highest detectivity reported for QDIP on InP substrate. 256×256 detector arrays were fabricated first time in the world for both the GaAs and InP based QDIPs. Dry etching and indium bump bonding were used to hybridize the arrays to a Litton readout integrated circuit. For the InGaAs/InGaP QDIP FPA, thermal imaging was achieved at temperatures up to 120 K. At T=77K, the noise equivalent temperature difference (NEDT) was measured as 0.509K with a 300K background and f/2.3 optics. For the InP based QDIPs, thermal imaging was achieved at 77 K.

A Conductive Atomic Force Microscope (C-AFM) has been used to investigate the nanometer scale electrical properties of Metal-Oxide-Semiconductor (MOS) memory devices with Silicon nanocrystals (Si-nc) embedded in the gate oxide. This study has been possible thanks to the high lateral resolution of the technique, which allows to characterize areas of only few hundreds of nm² and, therefore, the area that contains a reduced number of Si-nc. The results have demonstrated the capability of the Si-nc to enhance the gate oxide electrical conduction due to trap assisted tunneling. On the other hand, Si-nc can act as trapping centers. The amount of charge stored in Si-nc has been estimated through the change induced in the barrier height measured from the I-V characteristics. The results show that only ~20% of the Si-nc are charged. These nanometer scale results are consistent with those obtained during the macroscopic characterization of the same structures. Therefore, C-AFM has been shown to be a very suitable tool to perform a detailed investigation of the performance of memory devices based on MOS structures with Si-nc at such reduced scale.

Due to their simple implementation, low cost and good reliability for real-time control systems, semiconductor gas sensors offer good advantages with respect to other gas sensor devices. As gas adsorption is a surface effect, one of the most important parameter to tailor the sensitivity of the sensor material is to increase the surface area. For these propose, mesoporous oxides have been synthesized. Nanostructured mesoporous materials present a large and controllable pore size and high surface are. For the preparation of ordered nanostructure arrays, a hard template method has been used. This method presents some advantages when compared with a soft template method, especially in its specific topological stability, veracity, predictability and controllability. Moreover, with this hard template method we can obtain crystalline mesoporous oxides, with small particle size and high surface area. We have used SBA-15 (two-dimensional hexagonal structure) and KIT-6 (three-dimensional cubic structure) as a template for the synthesis of different crystalline mesoporous WO₃ with a particle size about 8-10 nm and high surface area. Low angle XRD spectra show a high order mesoporous structure, without rests of silica template. TEM confirms that the silica host has been completely removed; therefore, the nanowires constitute a self-supported superlattice. HRTEM studies have been focused on the detailed structural characterization of these materials. Electrical characterization of the sensor response in front of NO₂ has been performed. Some catalytic additives have been also introduced, in order to increase the sensitivity of the material.

In the present research, purified commercially SWCNTs are used as gas sensing material in an interdigitated electrode platform for NH₃, NO_x and H₂O detection. The SWCNT response to gas absorption is known to be dependent from different parameters and operational conditions, such as the relative orientation of the nanotubes and their organization between the electrodes, the temperature of the sensor, and moreover the voltage applied to a back gate contact. We show the sensor response for the various gas species considered and we analyze the sensor behavior with respect to the sensibility and to the detection velocity. Moreover we studied the effect on absorption/desorption gas processes by applying a gate voltage to the Si substrate beneath the interdigitated electrodes. The results indicate that the acceleration of the time response of the sensor for the detection of NH₃ is proportional to the gate voltage in the range 0 V - 40 V.

We have performed studies on the correlation between mechanical deformations and electrical conductance on a new interesting hybrid material, a Single Wall Carbon Nanotubes (SWCNTs)/Poly(3,4-ethylenedioxythiophene) (PEDOT) composite. Two are the synthesis techniques utilized to prepare the composite material in form of few hundreds of nm thick films: a spin coating deposition starting from an aqueous dispersion of SWCNTs and PEDOT, and an electrochemical de*position starting from a dispersion of SWCNTs and EDOT monomer. The composite conductance changes induced by a modulated periodic elongation via a coherent technique have been monitored by measuring the voltage variations of a Wheatstone bridge connected with the films. The measurements were performed on SWCNTs/PEDOT composites layered on a rigid substrate. The piezoresistivity gauge factor (GF) of the various samples was evaluated by comparing their responses to mechanical deformations to those of a commercial strain gauge, sticked on a substrate of the same kind. We found no significant piezoresistive effect in the hybrid material films deposited by means of spin coating while the effect is remarkable for the composites prepared by means of the electrochemical technique. In this case the gauge factor is found to be up to 3-4 times higher than that of the commercial strain gauge.

Organic semiconductors have attracted significant interest because of their potential application in electronic devices. One of the most important parameters in such an application is the carrier mobility, which is low when compared with the inorganic semiconductors. In the past, significant effort has been spent to produce high mobility organic semiconductors, even though the best room temperature value reported is only a few cm²/V.s. In this work, we examined the field-effect carrier mobility in pentacene by correlating reported data on polycrystalline samples with simulations based on the correlated disorder model (CDM). Using the rms width of the density of states (DOS) as the variable, we were able to produce a good match. Our results suggested that the carrier mobility in polycrystalline pentacene might be primarily dependent on σ, the rms width of the DOS. Furthermore, a parameter extraction scheme was proposed and applied to pentacene data reported in the literature.

Molecular cascades introduced in provide new ways to exploit the motion of individual molecules in nanometer-scale structures. Computation is performed by purely mechanical means similarly to the toppling of a row of standing domino. A specific feature of molecular cascades is that an inverter cannot be build, because it would require that all molecules in the inverter's output untopple when the input cascade topples. This is not possible because an untoppled state has higher energy than a toppled one. As a solution, we propose to avoid the need for inverters by representing signals by the dual-rail convention. As a basic building block we use a molecular block, which has four inputs x₁,...,x₄ such that x₃ = x'₁, x₄ = x' x₂, and two outputs ƒ₁ = x₁ • x₂ and ƒ₂ = x₃ + x₄. If input variables are available in both complemented and non-complemented form, then any Boolean function can be implemented by a composition of such molecular blocks. We present an experimental tool which first uses a rule-based randomized search to optimize a Boolean network and then maps it into a network of interconnected molecular blocks.

Surface enhanced Raman scattering (SERS) with 676.4 and 1064 nm excitations was used to investigate single-walled carbon nanotubes (SWNTs) compressed non-hydrostatically at 0.58 GPa, alone and dispersed into chemical reactive and non-reactive (SiO₂ and Al₂O₃) host matrices. As reactive host matrices, we used inorganic compounds (KI and Ag microparticles) and aromatic hydrocarbons (biphenyl, naphthalene, p-terphenyl, phenantrene). SERS spectra indicate that by compression, SWNTs break in fragments of different size, which in turn can react or not with the host matrix. Various mechanico-chemical reactions take place. In inorganic matrices such as KI and Ag, donor-acceptor complexes are formed. Regardless of aromatic hydrocarbons type used as organic matrices, i.e. with isolated or condensed phenyl rings, a non-covalent functionalization of SWNTs is produced. Using aromatic hydrocarbons with isolated phenyl rings like biphenyl or p-terphenyl, an ionic and covalent functionalization of SWNT fragments is demonstrated by the appearance of new Raman bands at 1160 and 1458 cm^-1, the latter being associated with the Ag(2) pentagonal pinch mode observed regularly in Raman spectra of C₆₀ fullerenes. The signature for the appearance of short fragments of carbon nanotubes, behaving as closed-shell fullerenes, is observed also in photoluminescence spectra carried out on SWNTs compressed in biphenyl and p-terphenyl matrix. Additional proofs are found by transmission electron microscopy (TEM) investigations.

Our paper is an overview of different methods, which were recently developed or adopted for the simulation of organic electronic devices. In the first part of this work we will briefly review state of the art approaches for simulating current flow through single molecules, while in the second and longer part we will focus on the design of architectures for molecular-scale computing. We will put special emphasis on field-coupling, which is a promising unconventional way for integrating a large number of molecules into a computing device.

The Finite-Difference Time Domain method has encountered several difficulties when analyzing dispersive materials. This is the case of the metal structures that configure an optical antenna. These devices couple the electromagnetic radiation to conform currents that are rectified by another physical element attached to the antenna. Both elements: antenna and rectifier configures an optical detector with sub-wavelength dimensions. In this contribution we analyze the effect on the currents induced by the incident electromagnetic field using FDTD and taking into account the dispersive character of metal at optical frequencies. The analysis is done in a 2 dimensional framework and it serves as an analytical tool for the election of material and structures in the fabrication of optical antennas.

By means of the microscopic transport description supplied by a semiclassical 2D Monte Carlo simulator, we provide an in depth explanation of the operation (based on electrostatic effects) of the nanoscale unipolar rectifying diode, so called self-switching diode (SSD), recently proposed in [A. M. Song, M. Missous, P. Omling, A. R. Peaker, L. Samuelson, and W. Seifert, Appl. Phys. Lett. 83, 1881 (2003)]. This device provides a rectifying behavior without the use of any doping junction or barrier structure (like in p-n or Schottky barrier diodes) and can be fabricated with a simple single-step lithographic process. The simple downscaling of this device and the use of materials providing high electron velocity (like high In content InGaAs channels) allows to envisage the fabrication of structures working in the THz range. With a slight modification of the geometry of the SSD, a lateral gate contact can be added, so that a nanometer self-switching transistor (SST) can be easily fabricated. We analyze the high frequency performance of the diodes and transistors and provide design considerations for the optimization of the downscaling process.

We reported the design and realization of a carbon nanotube-based integrated multielectrode device. Patterned Si/SiO₂/Nb/Nb₂O₅ multilayer was successfully realized by means of a few, common photolithographic processes with the minimum number of mask alignment steps. Such structure constitutes the patterned substrate of successive Hot Filament Chemical Vapour Deposition (HFCVD) process. Selective growth of highly oriented SWCNT arrays was obtained in the predefined locations while survival of the entire structure was achieved. Field emission measurements of such materials were carried out. Good and reproducible field emission behaviour has been observed in several realized structures.

Nanomagnets that exhibit only two stable states of magnetization can be used to store digital bits. This concept is already applied in today’s magnetic random access memories. Interacting networks of such nanomagnets with physical spacing on the order of 10 nm between them have been proposed to propagate and process binary information by means of magnetic coupling. These networks, called magnetic quantum-dot cellular automata (MQCA), offer very low power dissipation and high integration density of functional devices. In addition, MQCA can operate over a wide temperature range from sub-Kelvin to the Curie temperature of the applied ferromagnetic material. We demonstrate room temperature operation of logic gates made of NiFe alloy and fabricated by electron-beam lithography on silicon. Dipolar ordering in the nanomagnet-networks is imaged by magnetic force microscopy, and the operation is explained by means of micromagnetic simulations.

Resistance of biomolecules to high electric fields is a main concern for nanobioelectronics/nanobiosensing applications, and it is also a relevant issue from a fundamental perspective, to understand the dielectric properties and structural dynamics of proteins. In nanoscale devices, biomolecules may experience electric fields as high as 10⁷ V/m in order to elicit charge transport/transfer. Understanding the effects of such fields on their structural integrity is thus crucial to assess the reliability of biomolecular devices. In this study, we show experimental evidence for the retention of native-like fold pattern by proteins embedded in high electric fields. We have tested the metalloprotein azurin, deposited onto SiO₂ substrates in air with proper electrode configuration, by applying high static electric fields (up to 10⁶-10⁷ V/m). The effects on the conformational properties of protein molecules have been determined by means of intrinsic fluorescence measurements. Experimental results indicate that no significant field-induced conformational alteration occurs. This behavior is also discussed and supported by theoretical predictions of the intrinsic intra-protein electric fields. As the general features of such inner fields are not peculiar of azurin, the conclusions presented here should have general validity.

The emerging field of molecular electronics has brought together physicists, chemists, engineers and biologists. Large efforts on both, the experimental techniques and the theoretical methodologies, have led to fascinating developments in this field. It has been shown that the charge transport mechanisms at the molecular scale can considerably differ from those well-known in bulk solids. Phase coherent, ballistic transport as well as fully incoherent, hopping-like motion of the charge carriers may compete in determining the transport through a molecule. We review in this article basic facts related to charge transport and some of the theoretical approaches that have been developed to deal with this problem. We further show, in the special case of a DNA molecular wire, how the presence of a dissipative environment can appreciably modify the electronic spectrum of the system and thus lead to a change in its low-energy transport properties.

The conductance of nano-sized, surface disordered wires is theoretically analyzed all the way during an elongation process. Even though wire cross-section is kept constant during the whole process, the statistical analysis of the conductance reveals clear preference to take values close to integer multiples of the conductance quantum. We show that this is a consequence of having a very small number of channels and surface disorder only.

We study the electron transport in ultrathin silicon inversion layers with thickness in a range from 20nm down to 2nm by Monte Carlo simulation. Quantum effects are taken into account by simultaneously solving the Poisson and Schroedinger equations. Once the electron distribution in the silicon layer is known, the effect of a longitudinal electric field applied parallel to the silicon slab is studied. To do so, the Boltzmann transport equation is solved by the Monte Carlo method, and the electron mobility is evaluated. The influence of different scattering mechanisms has been analyzed. We show that two opposite effects appear on the electron mobility as the silicon thickness is reduced. On one hand the subband modulation effect, which contributes to an increase in the electron mobility. On the other hand, the greater confinement of the carriers as the silicon thickness decreases produces, as a consequence of the uncertainty principle, an increase of the phonon scattering rate, and therefore a decrease on the electron mobility. The superposition of these two opposite effects makes that electron mobility does not have a clear trend as the silicon slab thickness decreases.

We have produced alkali-metal encapsulated single-walled carbon nanotubes using a method of alkali-metal plasma ion irradiation. After plasma ion irradiation, alkali-metal encapsulated single-walled carbon nanotubes are sonicated for several hours in N,N-dimethylformamide to make well dispersed solution, then applied on a field-effect transistor substrate. As a result of measurements, pristine semiconducting single-walled carbon nanotubes show p-type conductivity, but Cs-encapsulated single-walled carbon nanotubes show n-type transport properties. This drastic change can be explained by electron transfer from encapsulated Cs atoms toward the surrounding SWNTs. At 11 K, the Coulomb oscillation is observed, implying that an inhomogeneous encapsulation profile of Cs atoms form several quantum dots. Thus, the electronic properties of SWNTs are found to be successfully controlled by plasma ion irradiation.

We investigated the influence of the surface state of diamond layers on the characteristics of the photoemission induced by 4.7 eV photons. A series of diamond samples grown by CVD under slightly different conditions have been analysed. Polycrystalline diamond layers with nanoscale graphitic patches embedded at the grain boundaries are found to exhibit unusually high efficiency of electron photoemission. The photoemitting properties of the different samples are rationalized by considering the electron emission process located at the a-C/diamond/vacuum triple border and the quantum efficiency (Q.E). governed by the ratio of amorphous sp²-C to crystalline sp³-C. At 4.7 eV values of quantum efficiency up to 1.5 x 10^-5 have been measured and the trends of the experimental Q vs J curves indicate that photoemission occurred mainly under one-photon regimes.

Modification of metal nanoparticles with laser light has been a well-known technique for several years. Still, selective tailoring of certain sizes or shapes of nanoparticles has remained a challenge. In this paper, we present recent studies on tailoring the size and shape of supported nanoparticles with continuous-wave and femtosecond pulsed laser light and compare them to our results obtained with ns pulsed laser light. The underlying method is based on the size and shape dependent plasmon resonance frequencies of the nanoparticles. In principle, irradiation with a given laser photon energy excites and heats nanoparticles of certain sizes or/and shapes and leads to diffusion and evaporation of surface atoms. Thus, tailoring the dimensions of the nanoparticles can be accomplished. In our experiments, gold and silver nanoparticles were prepared under ultrahigh vacuum conditions by deposition of atoms and subsequent diffusion and nucleation, i.e. Volmer-Weber growth. This gives particle ensembles with size and shape distributions of approximately 30% - 40%. The nanoparticle ensembles were irradiated with laser light either during or after growth. It turns out, that irradiation with cw or ns laser light makes possible selective modification of the nanoparticles. In contrast, application of fs laser pulses results in non-selective modification. For example, post-grown irradiation of supported gold nanoparticles with ns laser pulses (photon energy = 1.9 eV) causes a clear reduction of the width of the surface plasmon resonance from 0.52 eV to 0.20 eV (HWHM). Similar experiments were carried out with fs pulsed laser light (photon energy = 1.55 eV), which result in a slightly reduced line width but also, to an overall decrease of the extinction. A comparison of all experiments revealed, that for size or shape tailoring of supported metal nanoparticles best results have been achieved with ns pulsed laser light.

High quality luminescent CdS and CdSe nanocrystals, with tuneable band edge emission, were synthesized by means of thermal decomposition of precursors in organic solvents, incorporated in polystyrene and poly(methyl methacrylate) and deposited by casting, yielding optically transparent luminescent films. The obtained nanocomposite films were characterized by spectroscopical (UV-vis absorption and emission) and structural (TEM analysis) techniques. The effect of NC composition, concentration, size, and surface chemistry was evaluated in order to understand the role played by such factors in the nanocomposite optical properties for both the investigated polymers. The presence of organic ligand shell was demonstrated to be critical for the NCs incorporation into the polymer matrix.

In this work the host-guest chemistry of α-cyclodextrin has been investigated in order to mediate the phase transfer from organic solvent to water of blue emitting CdS nanocrystals. Oleic acid capped CdS nanocrystals have been synthesized by using colloidal chemistry routes in non-coordinating solvents and effectively transferred from hexane phase in aqueous solution. The transfer has been mediated by the formation of an inclusion complex between nanocrystal surfactant and α-cyclodextrins. The optical properties of the nanocrystal water solution, the effect of cyclodextrin concentration and the nanocrystal size on the phase transfer efficiency have been investigated. Finally a layer-by-layer assembling procedure of CdS nanocrystals complexed by cyclodextrins has been exploited to set up a supramolecular hierarchical multilayer system with high level of structural complexity.

A polymer microfluidic device for the formation of artificial bilayer lipid membranes (BLMs) on-chip is described. The device is fabricated from thin, transparent films of poly(methyl methacrylate), allowing for optical monitoring of the BLM. In addition, detection of single fluorescently-labeled lipid molecules using conventional epifluorescence microscopy is described.

In-situ annealed epitaxial (001) Ni films MBE grown on MgO substrates exhibit a missing-row (2x1) surface reconstruction due to oxygen adsorption. Thus, the resulting nano-patterning of the surface consists of self-assembled NiO nano-wires. Correlated RHEED, STM, XTEM, PNR and MOKE studies indicate that there is intermixing of the Ni film and the substrate with NiO formation at the interface between film and substrate and also on the surface of the films. This leads to the presence of an additional uniaxial magnetic anisotropy superimposed to the expected 4-fold magneto-crystalline anisotropy as determined with longitudinal MOKE.

Oxi-reduction processes of conducting polymer are the base of a great number of technological developments in the fields of polymeric actuators (artificial muscles) or smart windows. Hence, the understanding the structural changes that take place in the polymer as a function of its oxidation seems to be crucial for a proper understanding of these complicated systems. In this sense, a model with atomic detail has been simulated by Molecular Dynamics Simulation, which provides an insight of how the electrical response of the system depends of the structural changes that take place inside the polymer. In this regard, the conducting polymer, water and counterions were modeled with atomic detail with the goal of obtaining an insight of the ring orientation and reorientational relaxation time of the pyrrole rings at different oxidation states of the polymer. In addition, we studied how the above properties are greatly affected by the oxidation state of the polymer and the variation these properties changes from the polypyrrole/water interface to the polypyrrole bulk. Finally, we correlated the reorientational dynamics of pyrrole rings with the oxidation kinetic observed from a macroscopic point of view.

We present a structural, magnetic and magneto-optical (MO) study of Co nanoparticles sputter-deposited at different temperatures and embedded in three different matrices (two insulators such as MgO and AlN and a metal such as Pt). MgO capping layer does not affect the magnetism of the nanoparticles as demonstrated by in situ transversal and ex situ polar Kerr loops. The structure of the nanoparticles was investigated by TEM and a Co crystalline core surrounded by an amorphous crust was observed. From the analysis of the MO spectral response of the nanoparticles we demonstrate that the evolution of the MO constants as a function of Co concentration can be explained with the Maxwell-Garnett model. It is also observed that the reduction of nanoparticles size gives rise to a decrease of the relaxation time of the electrons into them. The deposition of Pt capping gives rise to the magnetic connection of the islands mediated by the polarised Pt, with the formation of different Co-Pt compounds as was observed with TEM. We observe that in the case of AlN capping destroys the magnetism of the samples due to a strong nitridation of Co.

Polycrystalline SiGe layers have been oxidized in either dry or wet atmospheres in order to form Ge nanoparticles embedded in a dielectric matrix. The evolution of the growing oxides and the SiGe layer during the oxidation processes have been characterized using Raman spectroscopy, X-ray diffraction, Rutherford backscattering and Fourier transform infrared spectroscopy. Ge nanocrystals have been formed in both oxidation atmospheres. Violet luminescence emission (3.1 eV) has been observed and its relation to the oxidation processes has been studied. For dry oxidation, the luminescence intensity appears suddenly when the pure segregated Ge layer starts to be oxidized forming Ge nanocrystals. It remains as long as Ge nanoparticles are present. For wet oxidation, an initial luminescence appears, that depends on the oxide thickness, which is related to the formation of Ge-rich nanoclusters trapped in the SiGeO growing oxide. A sharp increase of the luminescence for long oxidation times is then observed, which is related to the formation of Ge- nanoparticles by the oxidation of the segregated Ge. In both processes the luminescence is quenched for long enough oxidation time. The intensity of the luminescence in the dry oxidized samples, for equal initial thickness of the polycrystalline SiGe layer, is 10 times higher than in the wet oxidized ones. The violet luminescence is neither related to the recombination of excitons inside the Ge nanocrystals nor to defects in the germanium oxide. Ge oxygen deficient centers, located at the interface between the nanoparticles and the dielectric matrix, are proposed as the origin of the violet luminescence.

Using the solid-liquid-solid method, silicon nanowires were grown by annealing the gold-coated silicon substrates under the nitrogen flow. In this method, gold diffused into the silicon substrate upon heating and AuSi alloy formed at their interface. This alloy was melted when temperature increases above their eutectic point and percentage of Si presence in the mixture increased as heating continues. Rapid cooling occurred at the surface of these alloy melted when nitrogen gas was flowed into the chamber. This had caused the phase separation of the silicon from the surface of the alloy droplets and eventually self-arranged to form nanowires. Controlled growth of the nanowires was achieved by manipulating the annealing parameters. Relatively straight nanowires were produced by annealed the sample at 1000°C with nitrogen flow set to 1.5 liters per minute. The as-growth nanowires had diameters varied between 30 and 70nm. Heating duration was used to control the amount and lengths of the nanowires. Heating for 15 minutes produced less amount and shorter nanowires, while a 4-hour heating produced nanowires more than hundreds of microns long and with much larger amount.

The principle of the Orbitron pump is described. Its miniaturization is simulated. The application of such an ultra high vacuum pump is based on the availability of electron sources with good resistance against mbar vacuum levels. Especially field emitter cathodes are well suited to supply the active ionizing current. This electron current orbits around an anode. Ions generated along the electron path are extracted to the cathode. This is made from getter material e.g. titanium, which is sputtered by the impinging ions and in turn coats the internal surface of the pump. This generates an active getter film for chemical pumping. Employing a cathode - extractor separation smaller than 1 μm allows to start the pump at a pressure as low as 1 mbar in the cavity. Using electron beam induced deposition, it was shown that a field emitter - extractor configuration can be built with dimensions of < 2 μm in length, width and height. This miniaturized electron gun supplies the required current for the pump of e.g.100 μA. Employing micromechanical technologies, the Orbitron pump can be built and integrated into a MEMS device to supply UHV in a volume of < 1 Mio μm³ on a chip. Connecting the pump with a load vacuum volume, miniature electronic, optical, or mechanical devices, which require a continuous vacuum or even UHV, can be pumped down on chip and operated by only electrical controls.