A review of the subject of near-field optical imaging of metal nanoparticles is presented. The emphasis of the review is on experimental achievements in optical imaging of single metal nanoparticles and nanostructured arrays with metal nanoparticle building blocks. The importance of the measurements as they relate to nano-optical applications and scientific understanding of optical near-fields is highlighted. Advancements in scanning near-field optical microscopy (SNOM) that have enabled near-field images of these structures are also featured, as are theoretical contributions for interpreting SNOM images.

The scaling of complementary metal oxide semiconductor (CMOS) transistors has led to the silicon dioxide layer used as a gate dielectric becoming so thin (1.4 nm) that its leakage current is too large. It is necessary to replace the SiO2 with a physically thicker layer of oxides of higher dielectric constant (κ) or ‘high K’ gate oxides such as hafnium oxide and hafnium silicate. Little was known about such oxides, and it was soon found that in many respects they have inferior electronic properties to SiO2, such as a tendency to crystallise and a high concentration of electronic defects. Intensive research is underway to develop these oxides into new high quality electronic materials. This review covers the choice of oxides, their structural and metallurgical behaviour, atomic diffusion, their deposition, interface structure and reactions, their electronic structure, bonding, band offsets, mobility degradation, flat band voltage shifts and electronic defects. The use of high K oxides in capacitors of dynamic random access memories is also covered.

The kinetic modeling of low-pressure ($p\sim 1{-}10$ torr) stationary nitrogen discharges and the corresponding afterglows is reviewed. It is shown that a good description of the overall behavior of nitrogen plasmas requires a deep understanding of the coupling between different kinetics. The central role is played by ground-state vibrationally excited molecules, N2$(X\ ^1\Sigma_g^+,v)$, which have a strong influence on the shape of the electron energy distribution function, on the creation and destruction of electronically excited states, on the gas heating, dissociation and on afterglow emissions. N2$(X\ ^1\Sigma_g^+,v)$ molecules are actually the hinge ensuring a strong link between the various kinetics. The noticeable task done by electronically excited metastable molecules, in particular N2$(A\ ^3\Sigma_u^+)$ and N2$(a^\prime\ ^1\Sigma_u^-)$, is also pointed out. Besides contributing to the same phenomena as vibrationally excited molecules, these electronic metastable states play also a categorical role in ionization. Furthermore, vibrationally excited molecules in high v levels are in the origin of the peaks observed in the flowing afterglow for the concentrations of several species, such as N2$(A\ ^3\Sigma_g^+)$, N2$(B\ ^3\Pi_g)$, N2+$(B\ ^2\Sigma_u^+)$ and electrons, which occur downstream from the discharge after a dark zone as a consequence of the V-V pumping-up mechanism.

We present the modelling of twisted electromagnetic waveguides using helicoid coordinates. This amounts to introducing equivalent inhomogeneous anisotropic materials which are however taken into account easily by the finite element method. An interesting property of such helicoid coordinates is to preserve the intrinsically two-dimensional nature of the problem.

Non-ablative laser heating has recently turned out to be an efficient synthesis method for boron nitride (BN) nanotubes, offering flexibility in the control of experimental parameters. Long tubes are obtained as a hairy growth on the target around laser impact. Tubes are mostly assembled in bundles and thin. Selected area diffraction diagrams reveal that zigzag and armchair helicities are dominant, without preference. A field emission gun enabled to resolve the fine modulations in the diffraction diagrams for multi-walled nanotubes (MWNT) and for bundles of MWNT. The interpretation of the diffraction pattern of nanotubes is generalised for such modulations, considering the analytical expression of the diffracted amplitude at each graphite reflection. The fine modulations in the pattern are linked to roll diameters, bundle lattice, and interlayer distances. Experimentally, several roll diameter modulations are observed. Unusual modulations corresponding to an interlayer distance of 2 layers are also observed. They show a two-roll period, with an alternative shift along tube axis, in the piling of the rolls of MWNT.

Raman spectroscopy experiments correlated with infrared absorption, optical transmission and photothermal deflection spectroscopy ones are used to investigate in detail the short-range-order (SRO) and intermediate-range-order (IRO) in hydrogenated amorphous silicon (a-Si:H) films elaborated at high rates (~15 Å/s) by radiofrequency magnetron sputtering with various hydrogen dilution percentage (5 to 20%), leading to different hydrogen-related microstructure and content. The analysis of the transverse optic (TO)- and transverse acoustic (TA)-like modes of the Raman spectra indicates that both, the SRO and IRO are more strongly dependent on the nature of hydrogen bonding configurations, namely the relative proportion of polyhydride Si-H2 and (Si-H2)n complexes and/or clustered monohydride (Si-H)n groups incorporated in the films, rather than on the total bonded hydrogen content. The increase observed in the line width of the TO- and TA-like modes are well correlated with that of the disorder parameter E0, also called Urbach edge parameter, which is related to the exponential absorption from the valence band tails states distribution. Moreover, the analysis of the optical transmission data clearly evidences that the dispersion energy Ed and the static refractive index n0 are also maximum for films having the lowest value of E0, suggesting that they exhibit the highest mean coordination number and compactness respectively, consistent with better SRO and IRO.

In this paper, we present a simple model of Fowler-Nordheim (FN) current of metal/ultra-thin oxide/semiconductor (MOS) structures biased in the inversion mode ($V_{g }> 0$) (injection of electrons from the semiconductor). The oxide thickness varies from 45 Å to 110 Å, the gate is in chrome and the semiconductor is of P type. From the general models of the conduction by FN effect and by assuming a continuum energy in the inversion layer, we have shown by using the Wentzel-Kramers-Brillouin (WKB) approximation that the modeling of the FN current, cannot be made by using the classical model generally used in the case of electrons injection from the metal ($V_{g }< 0$). However, it requires to introduce in the classical model a corrective term due to the effects of the temperature, the oxide/semiconductor interface degeneracy (the Fermi energy is localized in the semiconductor conduction band) and the Schottky effect. The results obtained from the numerical simulation show that these effects, at the ambient temperature, on the potential barrier at the oxide/semiconductor interface is lower than 4% and the conduction pre-exponential value (K1) is higher than that obtained in the classical model ($K_1^o =10^{-6}$ A/V2) [J. Appl. Phys. 40, 278 (1969)]. These results are validated experimentally by modeling the current-voltage characteristics of MOS structures where the oxide thickness is 109 Å. For oxide thickness lower than 100 Å, we have found that the results of simulation disagree with those experimental. We have attributed this disagreement to the degradation of the conduction parameters by the presence of leakage current before stressing the MOS structure (LCBS). This leakage current is attributed to defects localized in the oxide layer. We have shown that the leakage current is of FN type and deduced the effective barrier of defects. By taking account of this barrier value and the corrective term due to the temperature, the oxide/semiconductor interface degeneracy and the Schottky effects (TDSEs), we have determined the defects effective area. From the comparison between these results and those obtained in the case of electrons injection from the metal ($V_{g} < 0$) [Eur. Phys. J. Appl. Phys. 9, 239 (2000)], we have concluded that the defects depth in the oxide layer is identical to the oxide thickness.

Multiwalled carbon nanotubes (MWNTs) were displaced on low-friction graphite surfaces in an easily controlled fashion by moving a voltage-applied tip of an atomic force microscope (AFM) across them. MWNTs on Si (5 5 12) surfaces were not displaced using the same electrostatic parameters. The friction at a Si (5 5 12) surface was measured to be 29 times larger than that of a graphite surface. We found that the electrostatic force applied to the MWNT was larger than the frictional force between the MWNT and the graphite surface, but much smaller than the frictional force on the Si (5 5 12) surface, allowing us to conclude that the electrostatic force may be responsible for the displacement of the MWNT on the graphite surface.

We report on the deposition of thin titanium carbide films on 60 mm and 100 mm Si wafers by KrF laser ablation of titanium targets in low-pressure (0.1 Pa) CH4 and C2H2 atmospheres, and on their characterization. The targets were titanium foils (purity 99.6%). Si (111) wafers, 60 and 100 mm in diameter, were used as substrates. Film characteristics (thickness, composition and crystalline structure) were studied as a function of the carbon-containing gas (C2H2 or CH4), laser fluence (4 or 6 J/cm2), substrate temperature (20 or 250 °C) and target-to-substrate distance (70–120 mm). Continuous, well adhesive polycrystalline TiC films were deposited even without any heating of the substrate. Films deposited in C2H2 ambient atmosphere are better crystallized and less prone to surface oxidation with respect to films deposited in CH4 atmosphere, in otherwise identical conditions.

This paper deals with the study of very low incident energy (0–12 eV) electron beam interactions with porous silicon (PS) substrates. It mainly concerns electron stimulated desorption (ESD) of negative H− ions ejected during a resonant bond breaking process. The experiments performed with a specific experimental set-up show that initially the PS surface was repulsive with regards to the low energy electron beam so that a reference voltage v0 = 2.44 V sets the origin of incident electron energy. Thus the resonant desorption process was centred at 7.5 eV with a threshold at 4.6 eV, close to characterisations on the hydrogenated surfaces of silicon crystals. However, the desorption yield was here very low in comparison. It was assumed that a large fraction of the incident electron beam entered the substrate depth enough without triggering significant ion desorption. Progressive shifts in the reference potentials up v0 = 5 V and significant reductions in desorption yield were caused by repeated electron bombardments with energies never exceeding 12 eV. These variations were attributed to changes in the surface composition of the porous silicon. It is assumed that residual fluorine atoms left after PS preparation might migrate towards the porous silicon surface as F− ions to enhance the electron beam repulsion. Following a general discussion, several experiments are suggested in order better to control modification of surface composition responsible for the ageing of the PS substrates.

Parallel Molecular Dynamics simulations are conducted for describing growth on surfaces with different kind of roughness: a perfect ordered crystalline flat graphite surface, a disordered rough graphite surface and flat surface with an ordered localized defect. It is shown that disordered rough surfaces results in a first step to reduction of the sticking coefficient, increased cluster density, size reduction. Structure of the clusters shows the disappearance of the octahedral site characteristic of compact structure. Isolated defect induces cluster-cluster interactions that modify growth compared to perfect flat surface. Kinetic study of growth shows power law tαz evolution for low impinging atom kinetic energy. Increasing kinetic energy, on all kinds of surfaces, results in a slightly larger exponent z, but fitting by an exponential function is quite good too. Lattice expansion is favoured on rough surfaces but increasing incoming atom kinetic energy weakens this effect.

In this paper we report a study of the magnetostatic coupling of square dot films and strips of films of Permalloy/Copper/Permalloy (200/20/200 nm). Results show a good magnetostatic coupling which leads to a monodomain structure in the case of square dots as it is observed from hysteresis loops. These monodomain structures appear to be stable for a wider range of dot dimensions rather than in monolayers. Magnetic simulations also support the existence of these kind of magnetic structures. Results obtained for strips are also reported. These samples exhibit a multidomain structure where it is possible to observe a coupling between domains and also between domain walls in the different magnetic layers.

Nanocrystalline PbSe films were grown on GaAs(100) and on the As face of GaAs(111) substrates using chemical solution deposition. The microstructure of the films was found to be strongly affected by the deposition temperature over a surprisingly narrow temperature range. In PbSe deposited on GaAs(100), gradual increase in crystallite size and transition to $\langle$111$\rangle$ texture were obtained with increasing temperature. In contrast with PbSe deposited on GaAs(100), the $\langle$111$\rangle$ texture in PbSe on GaAs(111) dominated throughout the deposition temperature range. Since temperature directly affects reaction rate, the temperature-dependent morphological changes observed in this work occur primarily due to increasing sample thickness.

Distinction between superhard coatings obtained by energetic ion bombardment during their deposition and superhard nanocomposites whose superhardness and high thermal and oxidation stability originates from a stable nanostructure is described together with the properties of the latter materials. The reasons for the poor reproducibility of our data as reported by some authors may be either an incorrect choice of a too low nitrogen pressure or temperature during the deposition or built-in impurities, or a combination of those.

Non-uniformity of temperatures appears as a general rule in hot nanofiber synthesis reactors, where local variations of the balance between long-range radiative heat exchanges and short-range conductive heat exchanges are driven by size and composition of structures. Metal particles larger than a few tens of nanometer are radiation captors, when fiber bodies thinner than 10 nm are transparent. We note that typical gradient lengths correspond remarkably well to usual length of nanotubes (micron range), and increase with fiber radius. For anisotropically radiating reactors as well as for furnace-type reactors, difference between radiative and conductive environments allows temperature intervals as high as several hundred degrees. Practically, axial thermal gradients arise by fiber attachment to a metallic particle, eventually at each tip (ideally with different sizes or compositions), or by attachment to a hot wall (electrode, supporting substrate, or target). The resulting thermal gradients are unusually stiff, typically 10 K µm−1. We show that local temperature evolution in early stage of nucleation is triggered by dimension of attached particle(s). We show that a diffusion flux of adatoms induced by the axial thermal gradient is quantitatively consistent with a feeding flux, as measured for different reactors. In addition, we notice that the spontaneous minimization of free energy at fiber tip is such that a temperature drop favors axial extension.

Removal of molecular atmospheric pollutants by non-thermal plasmas is under study since the beginning of the eighties. It has been shown that pulsed electrical discharges, such as dielectric barrier or corona discharges, are powerful means to eliminate Volatile Organic Compounds (VOCs) from the ambient air, or to treat flue gases which contain nitrogen oxide. However it is now recognised that, for several pollutants, the use of the plasma alone does not allow a complete elimination of the undesirable molecule. For example NO is oxidised in the air plasma to form other oxides like NO2 and N2O5, and reactions of oxygen atoms or hydroxyl radicals produced by the discharge with VOCs can lead not only to H2O and CO2 but to a number of by-products following the partial oxidation of the molecule, which can be as undesirable than the compound to be initially removed from effluents. This is particularly the case when the electrical energy deposited in the gas flow must be kept as low as possible in order to design a low energy cost equipment. As a result addition of a catalyst together with the pulsed discharge is now investigated in various laboratories in order to achieve a complete oxidation of VOCs, i.e. the so-called de-COV process, or a complete reduction of NOX (NO and NO$_{2})$ to produce N2 and O2, i.e. the so-called de-NOX process, at low energy consumption. This paper is a short review of works which have been done these last years in that domain, specifically on NOX and some selected VOC molecules.

Thin Eu2O3 films were prepared on Si (P) substrates to form MOS devices. The oxide films were characterised by X-ray fluorescence (EDXRF) and X-ray diffraction (XRD). The ac conduction mechanism and the dielectric properties of the oxide layers were studied at room temperature and in the temperature range of 290–420 K. We have also investigated the effect of the oxide-crystal structure on the surface density of states (Nss) at the insulator/semiconductor (I/S) interface. The method of capacitance-voltage (C − V) measurements was used to determine the Nss. It was concluded that the density of surface states in the mid-gap increases by about 30 times when the oxide Eu2O3 crystallises in polycrystalline form. Also, the density of the trapped charges in the oxide layer decreases by about 12 times when the oxide crystallises. The infrared studies inform us about the humidity incorporation in the oxide film in form of chemisorbed hydroxyl (OH) groups that leave the film for T > 373 K.

The spatial shaping of light beams is the process of redistributing the irradiance of a light beam. A correct beam shaping is essential to optimize a large number of laser-material processing applications and laser-material interaction studies. In this paper, after introducing the basic equations of the classical beam integration method to reshape and homogenize laser beams, we detail the design elements, the experimental performance and the main parameters of a novel transfocal homogenizer that is able to homogenize and reshape any light beam. Then we discuss the reliability of existing international standard parameters to evaluate the “goodness” of nearly flat-top shaped laser beams. Finally, we present examples of successful applications of this new homogenizer technology to ultraviolet irradiation experiments.

Metastable atoms play an important role in the kinetics of plasmas. A self-absorbing method has been used to determine the population density of Ar(3P0) and Ar(3P2) atomic metastable levels and Ar(1P1) and Ar(3P1) atomic resonant levels in an argon microwave discharge sustained by a surface wave at atmospheric pressure. Under the operative conditions investigated, the concentrations of these levels ranged from 1010−1012 cm−3, being in agreement with those reported in the literature, which seems to indicate that this method could be used for this calculation.

The effects of CO2 molecules upon an argon thermal plasma at atmospheric pressure are studied by optical emission spectroscopy. The excitation temperature, heavy particles temperature and electron density are measured as a function of Ar-CO2 mixture composition and discharge current. The excitation temperature is ranging from 7000 K to 12000 K, electron density from 3 × 1021 m−3 to 5.6 × 1022 m−3 and heavy particles temperature of the peripherical region of the column from 6000 K to 7000 K. Excitation temperature and electron density gradients are evaluated. The influence of the arc confinement is studied and departure from local thermal equilibrium is also discussed.