The ZrO2:Y2O3 solid solution formation has been followed by impedance spectroscopy and X-ray analysis. The experimental sequence, after mixing 8 mol% Y2O3 to ZrO2, was: attrition milling the mixture, drying, weighing, cold pressing, thermally treating at several different temperatures and times, performing the X-ray diffraction measurements at room temperature, applying metallic electrodes, and performing the impedance spectroscopy measurements in the 300°C-600°C temperature range. A good correlation was found between the decrease of the yttria main diffraction line and the increase of the stabilized zirconia main diffraction line, showing that solid solution is attained at the expenses of yttria, as expected. The impedance spectroscopy data Z(ω, T, t) show that the bulk response follows a t1/2 law, an evidence of yttrium diffusion to zirconia. Moreover, a relationship is found between the bulk resistivity and the elimination of ion blockers for increasing sintering times. The result allowed for the determination of the activation energy for the diffusion of the slowest diffusing species (Zr4+) in ZrO2:Y2O3.

Polyparaphenylene (PPP)-based carbon powder is expected for materials of the negative electrode of the lithium ion secondary batteries. In this study, effects of heat treatment temperature on the PPP materials are investigated by means of electrical and structural measurement. The layer structure of the powder is analyzed in detail by the transmission electron microscope observation combined with digital image processing. Charge-discharge current characteristics, electrical resistivity under pressure and layer structure of the PPP-based carbon powder are measured and discussed.

The anisotropic structure of EB polyaniline films cast from N, N'-Dimethylpropylene urea (DMPU) solution and stretched to different draw ratios was studied by infrared dichroism. The drawn films were doped with 1.0 M HCl and the electrical properties were studied by impedance spectroscopy. A new test fixture has been developed to measure the in-plane impedance of polymeric films. A Debye-like conductivity relaxation was observed for all the HCl-doped PANI samples. The conductivity along the stretch direction increases with molecular orientation. The in-plane conductivity is significantly higher than the through-plane conductivity.

We have used impedance spectroscopy to evaluate the effect of the presence of grain boundaries and plastic deformation, as caused by hardness indentation, on the electrical response of several commercial nickel base super-alloys at room temperature. These alloys consist of a mostly nickel matrix that contains small precipitates of intermetallic phases such as Ni3Al or Ni3Ti(often referred to as gamma prime) as a reinforcing phase. Measurements were made as point contacts so that data could be tracked from point to point. Results indicate that the grain boundaries tend to have higher conductivities than the individual grains in most cases. It is speculated that this is due to the boundary regions having a different compositional profile than the center of the grains(as determined by gamma prime size, shape and distribution). Hardness indentation, on the other hand, had a more dramatic effect, by causing the magnitude of the imaginary impedance to change in size as well as position. Complementary microscopy results are included as supporting evidence for the effects discussed.

The spatial variation of current density in lines with model void defects fabricated using Focused-ion Beam (FIB) milling has been investigated using Magnetic Force Microscopy (MFM). The model defects were designed to systematically simulate the natural void shapes that occur in electromigration failure of current-carrying lines. Inhomogenous current density around the defects manifests itself in the form of atypical asymmetry in the MFM signal near the defects. The extent of the asymmetry is greatly dependent upon the defect geometry. At current densities of 3-5×106 A/cm2, an asymmetry in the MFM signal is clearly visible around defects, such as a (1×1) μ,2 notch and a (1×9) μm2 45°-slanted slit, at the edge of a 10μm wide line. We present a survey of MFM images of various defect structures in current-carrying lines that perturb the homogenous current flow of a straight line.

Rapid thermal annealing (RTA) of lattice damage created by heavy ion implantation damage is required to maintain the integrity of semiconductor material used for submicron-integrated circuit devices. A quick, efficient, and contactless diagnostic of the implantation damage is highly desirable in both research and production environments. A contactless measurement technique has been recently applied to this problem that uses a deeply penetrating low-frequency microwave probe frequency operating at 420 MHz. Here, we will demonstrate the use of this high frequency resonance-coupled photoconductive decay (RCPCD) technique, which, when combined with a tunable optical excitation source, enables us to map the radiation damage in boron and arsenic-implanted silicon wafers. We quantify the damage by mapping the minority-carrier lifetime as a function of optical penetration depth. In this work, we quickly and efficiently compared the effectiveness of various RTA processes by the RCPCD diagnostic.

The electronic structure of AlS9 tilt grain boundary with segregated impurity atoms of Na, Ca, Si and S, respectively, has been investigated by an ab initio pseudopotential method. Na and Ca segregation causes the boundary to expand and the charge density to decrease significantly. There forms several weak bond regions. Si segregation increases the charge density between Si and the neighboring Al atom. There forms a stronger Al-Si bond that is a mixture of covalent and metallic character in the boundary. For S segregation, though there forms the stronger bond between Al and S atom, some Al-S bonds may become weaker than the former Al-Al bonds because of the charge density decrease. It is concluded that the mechanism of Na or Ca-promoted Al grain boundary embrittlement is one kind of ‘decohesion model’, that of Si is ‘bond mobility model’. It can't be decided the embrittlement mechanism by S segregation is classified into ‘bond mobility model’ or ‘decohesion model’.

We have developed the electrochemical porosimetry analyzing microstructures of porous electrodes, which can give geometric information most meaningful in electrochemical systems. The methodology is based on the transmission line model with pore size distribution (TLM-PSD) that relates electrochemical impedance data with microstructural information. Pore length (lp), as well as pore size distribution, can be obtained by fitting the TLM-PSD to the experimental impedance data of a porous electrode. This geometric information was validated for the microporous, mesoporous and macroporous samples by comparing with the data obtained from conventional porosimetry. It was also shown that the electrochemical porosimetry could be used as a nondestructive probe to investigate the construction of electrochemical devices.

The electron energy-loss near-edge structure (ELNES) and x-ray absorption near-edge structure (XANES) at the oxygen K-edge has been investigated in a range of yttria-stabilised zirconia (YSZ) materials. Analysis of near-edge structure reveals that both the crystallographic phase and the metal fraction of yttrium present can be determined directly from the oxygen K-edge data. Simulation of the ELNES/XANES was achieved using a pseudopotential based method to obtain the relaxed atomic coordinates combined with full-potential LMTO method to calculate the electronic structure.

Composite patching method is widely applied for repair cases of metallic aircraft structures due to more efficient performance than conventional repairs. However, the detection of structures integrity under patch, during the service life of aircraft, by non-destructive means is considered of great importance. In the present study, different NDT techniques such as active infrared thermography, eddy currents and electrical impedance spectroscopy, were applied for the detection of simulated artificially introduced damages - notches, on the surface of aluminum aircraft skin panels, Al 2024-T3, under composite patching (carbon reinforced laminates). The detection sensitivity of each technique was investigated based on the relation between thickness of composite patch and specific parameters of each method aiming at the development of a reliable, for this purpose, quality inspection technique.

X-ray diffraction and resistivity measurements on the Al72Mn22Si6 (Al-Mn-Si) rapidly quenched alloy are reported. The x-ray pattern shows that the alloy is essentially single phase, with a little mixture of unreacted Al. The peaks can be indexed using icosahedral vectors in the six dimensional space Z6. The resistance of thin ribbons of Al72Mn22Si6 quasicrystals has been measured as a function of temperature between 1.4 and 300 K at fixed pressures in the range 0 to 15 Kbar. Below 40 K, the resistance increases with decreasing temperature, and below 14 K, the conductivity varies as T1/2. This result is in agreement with the scaling and localization models in which spatial disorder and electron-electron correlation effects determine the electronic transport properties of the material. The value of the magnetoresistance measured at 60 KGauss and 0.34 K agrees qualitatively with the predictions of the above models. The pressure dependence of the correlation gap and the resistivity suggests that the system is in the strong coupling limit. In this regime, the functional dependence of the correlation energy on resistivity is Δ ~ ρ-2.

Effects of porosity on the microwave properties in dielectric ceramics were studied by the electromagnetic simulation. Scattering matrix S21 obtained from the network analyzer was compared to the S21 obtained from the simulation. From electric field distribution, the dominant resonant TE01 mode could be easily determined. The effects of the porosity inside the dielectrics on the microwave properties were investigated. Quality factor decreased with the porosity and the pore size.

Anodic tantalum pentoxide is studied up to 3 GHz by using for the first time the Radio-Frequency Impedance Analysis. Over this broad frequency range we extract a better knowledge on the very physical nature of this dielectric. From impedance analysis we obtain the value of the leakage conductance in parallel to the pure capacitance. At frequencies higher than 1 MHz capacitance vanishes to zero. This behaviour appears for all the samples, independently of thickness, anodization precursor or electrode metals, suggesting that it should be due to some intrinsic property of the dielectric. The electrical response of amorphous tantalum oxide is due to dipole oscillations characterized by a constant time; when frequency is high enough, dipoles do not have time to follow the field oscillations and, as a consequence, there is not any capacitive behaviour.

Impedance spectroscopy (IS) is a powerful characterization methodology for a wide range of electric materials such as ceramics, ferroelectrics, ion conductors, piezoelectrics, etc. In this paper, an extension of IS to the case of ferromagnetic materials is presented. In particular, the resolution of the most common magnetization processes (domain wall bulging, domain wall displacement and spin rotation) is analyzed. IS is applied to ferrites and giant magnetoimpedance in amorphous wires.

The dynamics of the photogenerated carriers in porous silicon and TiO2 anatase was studied at 35 GHz by measuring the change in time of the conductivity s and dielectric constanter. Localization of carriers leads to a positive change ofer, while quasifree carriers to a negative change. Size reduction in Si shortens the recombination time as long as the surface traps are not significant. Magnetic field investigations show opposite variation of conductivity in poroussilicon compared with TiO2.

Abstract:Impedance spectroscopy has long been recognized as one of the major techniques for the characterization of ac transport in materials. The primary limitation of this technique is the lack of spatial resolution that precludes the equivalent circuit elements from being unambiguously associated with individual microstructural features. Here we present a scanning probe microscopy technique for quantitative imaging of ac and dc transport properties of electrically inhomogeneous materials. This technique, referred to as Scanning Impedance Microscopy (SIM), maps the phase and amplitude of local potential with respect to an electric field applied across the sample. Amplitude and phase behavior of individual defects can be correlated with their transport properties. The frequency dependence of the voltage phase shift across an interface yields capacitance and resistance. SIM of single interfaces is demonstrated on a model metal-semiconductor junction. The local interface capacitance and resistance obtained from SIM measurements agrees quantitatively with macroscopic impedance spectroscopy. Superposition of a dc sample bias during SIM probes the C-V characteristics of the interface. When combined with Scanning Surface Potential Microscopy (SSPM), which can be used to determine interface I-V characteristic, local transport properties are completely determined. SIM and SSPM of polycrystalline materials are demonstrated on BiFeO3 and p-doped silicon. An excellent agreement between the properties of a single interface determined by SIM and traditional impedance spectra is demonstrated. Finally, the applicability of this technique for imaging transport behavior in nanoelectronic devices is illustrated with carbon nanotube circuit.

The standard percolation equations or power laws, for dc and ac conductivity (dielectric constant) are based on scaling ansatz, and predict the behaviour of the first and second order terms, above and below the percolation or critical volume fraction (øc), and in the crossoverregion. Recent experimental results on ac conductivity are presented, which show that these equations, with the exception of real σm above øc and the first order terms in the crossover region, are only valid in the limit σi/σc = 0, where for an ideal dielectric σi=ωε0εr.

A single analytical equation, which has the same parameters as the standard percolation equations, and which, for ac conductivity, reduces to the standard percolation power laws in the limit σi(ωε0εr)/σc = 0 for all but one case, is presented. The exception is the expression for real σm below øc, where the standard power law is always incorrect. The equation is then shown to quantitatively fit both first and second order dc and ac experimental data over the entire frequency and composition range. This phenomenological equation is also continuous, has the scaling properties required at a second order metal-insulator and fits scaled first order dc and ac experimental data. Unfortunately, the s and t exponents that are necessary to fit the data to the above analytical equation are usually not the simple dimensionally determined universal ones and depend on a number of factors.

As it has been shown elsewhere, conductance transient measurements provide quantitative information about the disordered induced gap states (DIGS) in metal-insulator-semiconductor (MIS) structures. In this work we report for the first time the DIGS spatial and energetical distribution obtained by recording conductance transients at several temperatures (ranging from 77 to 300 K) and several frequencies (ranging from 100 Hz to 200 KHz). These measurements allow us to obtain three-dimensional defect maps of Al/SiNx:H/InP structures browsing ranges of 0.5 eV in energy and 40 Å in depth. Our results show that this technique is a very useful tool for the electrical characterization of MIS structures and reveals itself as very valuable in the III-V semiconductor-field-effect transistor scenario.

The capacitance detection techniques, applicable to Scanning Capacitance Microscopes, have been analyzed from the point of view of signal-to-noise ratio that finally affects the achievable lateral resolution. It was found that comparable sensitivities can be achieved from relatively low frequencies below 1 MHz up to the GHz region. On conducting surfaces, resolution better than 5 nm has been achieved. It is limited by the minimum probe-to-sample distance, below which large tunneling current would occur. Increasing the applied voltage above a few volts increases the sensitivity at the cost of lateral resolution, since, at high voltage and small probe-sample distance, field emission could occur.

A buffered dielectric measurement method is described. We added a thin buffer polymer layer to a polymer film before depositing aluminum electrodes. This is a modification to conventional parallel plate dielectric constant measurement method. It still has well-defined geometric factor for determining the dielectric constant. We designed the buffer layer using a simple RC model. It was determined that the buffer layer should be a high dielectric constant polymer. Two high dielectric constant polymers were selected to be buffer layers. Layered samples with structures ABA and ABC were discussed, where A is the buffer layer. We show that the method not only provides a way to preserve the structure of special polymer films, but also is able to adjust its electrical characterization to a convenient level.