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.

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.

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.

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.

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.

Contact electrification and triboelectrification are well-known in the case of dissimilar materials, however the case of charge exchange during friction between nominally identical insulating materials is less documented. We experimentally investigated the triboelectrification between two smooth monocrystalline $\alpha $-Al2O3 (sapphire) antagonists by surface force measurements with a Surface Force Apparatus (SFA). The force between a sphere and a plane, both in sapphire, was measured as a function of the sphere-plane distance D, before and after nano-friction tests, under dry argon atmosphere. Respective contributions of van der Waals, water meniscus and electrostatic forces were determined. The estimated Hamaker constant was in good agreement with the Lifshitz theory, and the dominant meniscus attraction at low separation could be overcome with small radius sphere. We demonstrated that electrostatic forces were generated by the nano-friction test and we quantified the adhesion that results from this contact-electrification. In the first stage of the unloading process, the short range electrostatic force was found to vary both with time and distance D. Experimental results were correlated with surface densities of mobile charges on the two surfaces, and the time-dependence was related to classical surface transport phenomena on alumina surfaces.

The structure and magnetic properties of the nanoparticles of immiscible system Co20Cu80 prepared by means of arc-discharge, have been studied in detail. The diameters of the particles are about 20 ~ 30 nm and a core/shell structure forms. The cores are Co-Cu solutions, which show some small Co precipitates, encapsulated with a shell of cupper oxide or cobalt oxide as observed by means of high-resolution transmission electron microscope (HRTEM) and energy dispersive X-ray (EDS). The loop shift in the hysteresis loop indicates the existence of the exchange bias between ferromagnetic and antiferromagnetic components at low temperatures. A block temperature about 180 K has been observed for as-deposited nanoparticles. For the annealed nanoparticles, the thermal magnetization at low temperatures is satisfied with Bloch's law. 


We used an in-plane magnetized electrode and a perpendicular to film plane magnetized multilayer electrode in a magnetic tunnel junction to generate the active part of a magnetic field sensor able to measure large fields. When the applied field is normal to the junction surface, the magnetization of the multilayer electrode is fixed while the moment of the in-plane magnetized electrode rotates towards the applied field. This generates a linear variation of tunnel junction resistance with the applied field. The use of tunnel junctions with all their known advantages makes this structure attractive for measuring large magnetic fields, of up to several kG.

2K+ to K + K2+ and K to K3+ provide a reaction with a net enthalpy equal to one and three times the potential energy of atomic hydrogen, respectively. The presence of these gaseous ions or atoms with thermally dissociated hydrogen formed a so-called resonance transfer (rt)-plasma having strong VUV emission with a stationary inverted Lyman population. Significant line broadening of the Balmer $\alpha $, $\beta $, and $\gamma $ lines of 18 eV was observed, compared to 3–4 eV from a hydrogen microwave plasma. Emission from rt-plasmas occurred even when the electric field applied to the plasma was zero. The reaction was exothermic since excess power of 20 mW cm−3 was measured by Calvet calorimetry. An energetic catalytic reaction was proposed involving a resonant energy transfer between hydrogen atoms and 2K+ or K to form very stable novel hydride ions H−(1/p) called hydrino hydrides having a fractional principal quantum numbers p = 2 and p = 4, respectively. Characteristic emission was observed from K2+ and K3+ that confirmed the resonant nonradiative energy transfer of 27.2 eV and 3 × 27.2 eV from atomic hydrogen to 2K+ and K, respectively. The product hydride ion H−(1/4) was observed spectroscopically at 110 nm corresponding to its predicted binding energy of 11.2 eV. The 1H MAS NMR spectrum of novel compound KH*Cl relative to external tetramethylsilane (TMS) showed a large distinct upfield resonance at −4.4 corresponding to an absolute resonance shift of −35.9 ppm that matched the theoretical prediction of p = 4. A novel peak of KH*I at −1.5 ppm relative to TMS corresponding to an absolute resonance shift of –33.0 ppm matched the theoretical prediction of p = 2. The predicted catalyst reactions, position of the upfield-shifted NMR peaks for H−(1/4) and H−(1/2), and spectroscopic data for H−(1/4) were found to be in agreement with the experimental observations as well as previously reported spectroscopic data for H−(1/2) and analysis of KH*Cl and KH*I containing these hydride ions.

An effort for better understanding of main parameters influence to polystyrene thin films treatment under DC point-to-plane low-pressure discharge in nitrogen is attempted. Voltage-current curves and discharge repetitive current impulses for various gap lengths and gas pressures, in absence and in presence of polystyrene thin films in the cold plasma reactor, evidence that in any case a normal glow discharge regime is established. Atactic polystyrene thin films underlie treatment under the above regime and hydrophilic surfaces are obtained. Wettability is characterized, under certain experimental protocols, by contact angle measurements along the films treated for various gap lengths (d = 0.5, 1, 2 cm), gas pressures (p = 2-10 mbar), gas flow rates (Q = 1-1110$ sccm) and times (ttr = 0-600 s). The best treatment takes place opposite to the point electrode, in an area around the discharge symmetry axis, proving non-homogeneous surface treatment. Atomic Force Microscopy (AFM) shows that this fact does not relate to surface morphological changes. The experimental results confirm that the above treatment yields polystyrene films with very good wettability (typical contact angles: 5-15°) avoiding any obvious material degradation. Ageing effects are introduced but the final wettability in comparison to that before the treatment is increased. The role of excited neutrals and reactive particles with long radiative lifetime (metastables states) is emphasized and seems to lead to polymer treatment through diffusion mechanisms.

The plasmadynamics of a stationary plasma thruster (SPT-100) plume in the very-near-field region have been studied by using a two-dimensional axisymmetric numerical code based on a combination of Particle-in-Cell (PIC) simulation for ion component (Xe+ and Xe++) and fluid description for electrons. In particular we have solved the electron momentum conservation equation (including collisional and magnetic effects) and the electron energy conservation equation (including collisional effects). Due to the difference between electron and ion Larmor radius and to the effect of the thruster wall, the quasi-neutrality hypothesis can be violated in the very-near-field plume region and the electric field must be computed accordingly. The xenon atom flowfield is calculated analytically. The model allows a unitary rationalization of several experimental observations.