In this work, nanocrystalline lead telluride powder was synthesized from high-purity elements by mechanical alloying by means of a planetary ball-milling procedure. The milling medium was tungsten carbide, and the diameter of the balls was varied in order to investigate the effect on the structural features of the material. Phase transformations and crystallite evolution during ball-milling were followed by powder x-ray diffraction (PXRD). The broadened PXRD peaks were analyzed with Voigt functions, revealing small crystalline size and stress introduced during the mechanical alloying process. Transmission electron microscopy (TEM) studies confirmed the material’s nanostructure, as well as the effect of ball diameter on the size of the crystals. Thermoelectric properties are discussed in terms of the Seebeck coefficient and the nominal carrier concentration, as determined by Hall-effect measurements. The enhancement of the Seebeck coefficient is reported to be higher compared with other PbTe-based nanocomposites.

We present a detailed study of the microstructure and morphology of a very wide variety of binary transition metal nitrides (TiN, ZrN and TaN) grown by pulsed laser deposition (PLD) as well as of ternary nitrides consisting of Ti alloyed with Ta or Zr. We also present a critical investigation of their electronic properties such as the plasma energy, electrical resistivity and work function, with respect to their composition, microstructure and the electronic structure of the constituent metals using optical reflectance spectroscopy, Hall effect and Kelvin probe measurements.

A series of nanocrystalline Co/Au multilayers with ultrathin Au interlayers was grown at room temperature by electron beam evaporation on Si(111), glass and polyimide substrates. X-ray diffraction measurements reveal a face centered cubic multilayered structure with very small nanograins within 7-10 nm in diameter. Magneto-optic polar Kerr effect experiments show an enhancement of the Kerr rotation around 3 eV as the Au interlayer thickness increases. The experimental data are interpreted with the help of simulated Kerr spectra. The magnetization curves and magnetic force microscopy images indicate the existence of perpendicularly magnetized stripe-domain structures at remanence. The magnitude of the magnetoresistance ratio reaches values of 0.4%. The investigation of the interplay between magnetic and magnetotransport properties demonstrates the contribution of the domain-wall spin-dependent scattering to the magnetoresistance.

The structure and magnetism of Au/Co multilayers grown on patterned substrates are investigated. The structure and morphology are studied by means of X-ray diffraction spectra and atomic force microscopy images revealing that the magnetic film deposition retains the topography of the substrate. The magnetic behavior is studied by using the magneto-optic Kerr effect spectroscopy revealing similar response in patterned and non-patterned samples. Finally, magnetotransport measurements show enhanced magnetoresistance values by 35% on patterned samples.

Arrays of Pt and Polymethyl methacrylate (PMMA) orthogonal stripes were patterned on Si substrates by e-beam lithography. Co/Pt multilayers were deposited on these substrates, by e-beam evaporation. Scanning electron microscopy and atomic force microscopy images show that the multilayer growth maintains the patterned morphology. The magnetoresistance effect has been investigated in patterned and non-patterned multilayers at room temperature.

A method of multicarrier analysis of semiconducting β-FeSi2 thin films is described, based on Hall and magnetoresistance data from variable magnetic field measurements. We exploit both the longitudinal and transverse resistivity components to extract the concentration and mobility of each carrier. Nonlinear fitting is used to fit simultaneously the magnetoresistivity and Hall resistivity data versus the magnetic field. The criteria and the procedure, as well as the selection of a proper function for minimization are discussed. Application of the proposed method in β-FeSi2 thin films revealed the presence of multiple carriers, explaining the nonlinear dependence of the Hall voltage on the magnetic field. Analysis of the Hall data at various temperatures revealed the most probable scattering mechanisms and a thermally activated behavior of the carrier concentration.

We apply the Lippmann‐Schwinger equation for obtaining the scattering amplitudes and conductance as a function of Fermi energy for electrons scattering from one and two point defects in a two‐dimensional quantum wire. Further, we discuss the first and higher‐order Born approximation to the scattering wave function and show that keeping five terms in the Born series can lead to a convergent wave function (except for Fermi energy close to the subband energy where it naturally diverges). It has been stated previously that electron transmission through a single point defect in a quantum wire is perfect at every subband minima independent of where the scatterer is located. However, here we demonstrate that perfect transmission at subband minima is strongly affected by the transversal position of the defect. In particular, we show that the perfect transparency effect is modified when the scatterer is located at the nodes of a normal confinement mode.

Ag–Co multilayers with very thin Co layers exhibit self-organized nanogranular structure and large values of giant magnetoresistance (GMR). In this work, a third non-magnetic element X (X=Cu, Pt, Si) is added to the Ag layer and the influence of this modification on the structural, magnetic and magnetotransport properties of the samples is examined. We find that the addition of Cu maintains the granular structure and large magnetoresistance values. On the contrary, the samples turn into multilayers with continuous Co layers and small magnetoresistance with increasing Pt concentration. Small magnetoresistance values are also exhibited by the AgSi–Co samples. Post-deposition annealing of the Ag–Co and AgX–Co systems is examined and found to result in structural improvement of the films accompanied by monotonic GMR magnitude decrease.

Metallic Li anode present serious problems, so we are applying the concept of an inert matrix to shield a battery anode, proposed by Huggins 15 years ago (Wang et al., 1986); Today, carbon anode based Li-ion polymer electrolyte batteries' technology is enjoying wide commercial success. However certain carbon material forms as well as liquid electrolyte interfacial (Winter et al, 1999) electrode complexities keep the anode part of the Li-ion batteries still open. Lithium alloys possess high capacity and energy densities (Wang et al., 2000). Silicon was used at elevated temperatures lithium batteries (Weydanza et al., 1999). Bulk silicon's lithiation of at room temperature presents very slow kinetics (Weydanza et al., 1999). The morphology of silicon as candidate lithium anode material seems to be a key parameter since silicon films presented good perfomance (Bourderau et al., 1999). In this work we present a new form of microcrystalline ceramic silicon prepared from pure silicon powders as candidate lithium anode at room temperature.

We study the effects of the shape of the cross section of a three-dimensional quantum wire on electron scattering from a single point defect in the wire. The confinement of electrons is modeled by both hard- and soft-wall potentials. We find that as the degree of anisotropy of the cross section of the wire is increased intersubband electron scattering is enhanced and intrasubband transmission is suppressed making it appear as though the defect has stronger impact on electron scattering for asymmetric cross sections. Also, increasing the anisotropy of the cross section results in a decrease of the values of the conductance. Furthermore, for the soft-wall confinement the conductance as a function of Fermi energy rises faster than the conductance for the hard-wall confinement. We use the Lippmann–Schwinger equation of scattering theory in order to calculate analytically the transmission coefficients.

The effect of Pt doping on the Ag layers of granular Ag-Co multilayers is studied. Studies performed via X-ray diffractometry and transmission electron microscopy reveal a structural transition of the samples from granular to multilayer form dependent on Pt concentration. Magnetic hysteresis appearance and magnetoresistance ratio reduction also support the structural transition.

The Ag–Co system either in multilayer or in granular alloy form exhibits the Giant MagnetoResistance (GMR) effect. By adjusting the modulation parameters an intermediate structure may be formed offering new possibilities for magnetoelectronic applications. This structure resides in the limit between multilayers and granular alloys and is called granular multilayer. This work deals with the Ag–Co system and involves film growth by e-beam evaporation, structural characterisation by X-ray and TEM facilities together with magnetic (SQUID) and magnetotransport measurements. The dependence of GMR values on the individual layer thickness and on the total film thickness was parameterised and magnetoresistance values of 16% at 300K and 36% at 30K were achieved. The outcome of this study is the fabrication of a two-dimension magnetic field sensor consisting of eight specific elements forming a 2×4 array. The sensor is specialised in small magnetic field regions while its response was found quite satisfactory regarding its uniformity and repeatability. The sensor may be upgraded to larger arrays and to three dimensions in order to fulfil various market needs.

Titanium nitride (TiNx) thin films, ∼100 nm thick, were deposited on Si(100) substrates by dc reactive magnetron sputtering. The effects of the substrate bias voltage and deposition temperature on their optical, electrical, and mechanical properties have been studied. It was found a strong correlation between the electrical and mechanical properties of the films which are significantly improved with increasing the substrate bias voltage and the deposition temperature. The low resistivity (43 μΩ cm), combined with the high hardness and elastic modulus values, suggest the TiNx as a promising metallization material in Si technology.

The electrical transport properties of polycrystalline semiconducting β-FeSi2 films have been evaluated by conductivity (σ) measurements over the temperature range 50–300 K. At low temperatures (T<200 K), a variable range hopping conduction was observed, from which the number of states near the Fermi level and the degree of disorder in the material were obtained. At moderate temperatures (200–300 K), the ln σ vs 103/T curves show anomalous features such as kinks or continuous bending. In this temperature range, the conductivity data satisfy the Meyer–Neldel rule, (MNR), which is of fundamental importance for the transport properties of the β-FeSi2. The results show that the MNR parameters are related with the degree of disorder in the material.

Magnetic properties of a series of Mg-doped granular samples were studied by means of vibrating-sample and SQUID magnetometry. The equilibrium moment measured after the sample demagnetization gave evidence that the surface barrier effects can be neglected up to 60 K. Slope of the high-field dependence was used for determination of the temperature dependence of the penetration depth and its extrapolation to T = 0, . The latter quantity was found to be significantly affected by the expression used for the data fit. The irreversible moment deduced from the magnetic hysteresis loops showed a pronounced fishtail effect. In the temperature range 50-60 K, the curve was found to scale in a similar manner as in (RE)-123 single crystals. The conventional relaxation rate dramatically changes at the fields around the remanent state. The field range of this anomaly coincides with the central peak width, and we attribute this effect to redistribution of the magnetic flux in the sample. A simple non-monotonic dependence was observed of the fishtail maximum position on the nominal Mg content. A similar but mirror dependence was found of .