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Abstract: This study Density functional theory method have been utilized in order to accomplish the electronic properties and diagnosis the ligand-metal nanoclusters (3B5)Ag, (3B5)Cd, (3B5)Cr, (3B5)Cu, (3B5)Mo, (3B5)Nb, (3B5)Ni and (3B5)Zn through sophisticated algorithms in Gaussian 09, Gauss-view 05 programs. Density of states of all coordination complexes nanoclusters in this treatise have been accomplished by using Gausssum 03 program. The characterstics molecular geometry of the ligandsmetals nanoclusters, electrostatic potentials (ESP), contour density maps, diagnostics by infrared spectra (IR), Density of states (DOS), HOMO energy, LUMO energy, SOMO energy, Energy gap (Eg), ionization potential (I.P), electron affinity (E.A), dipole moment in (Debye) and the polarizability in (a.u). Photos of electrostatic potentials and contour maps demonstrate that the electronic charges assemble around some atoms, but disappear around other atoms. Diagnostic by IR shows the active regions and the wave numbers in (cm-1) unit that correspond to the suitable bond lengths and wavelengths. Density of states schematics clarifies entity two types of orbitals alpha and beta in the coordination complexes nanoclusters (3B5)Cd, (3B5)Cr, (3B5)Mo, (3B5)Ni and (3B5)Zn, but only alpha orbitals in the coordination complexes nanoclusters (3B5)Ag, (3B5)Cu and (3B5)Nb. (Energy of HOMO and LUMO) and Energy gap (Eg) table summarizes presence two types of materials, semiconductors and insulator, only the coordination compolexes nanocluster (3B5)Cu has insulator properties. It has energy gap approximately (6.775 eV), but the other coordination complexes nanoclusters have semiconductor energy gap. Ionization potential and electron affinity table summarizes strength of donor and acceptor. Dipole moment table demonstrates that is no zero values of the dipole moment, because all coordination complexes nanoclusters in this treatise are heterogeneous, i.e. each one of them possess two types of atoms Boron atom and the metal atom. The maximum value of the average polarizability is for the coordination complex nanocluster (3B5)Nb, which pretty much equal to (374.2 a.u), hence this coordination complex nanocluster is the maximum activity among the paradigms in this treatise. All coordination complexes nanoclusters has the point group symmetry (C2v/C1). [ABSTRACT FROM AUTHOR]

In0.53Ga0.47As p + n diodes with different densities of extended defects have been analyzed by detailed structural and electrical characterization. The defects have been introduced during Metal-Organic Vapor Phase Epitaxy (MOVPE) growth by using a lattice-mismatched layer on a semi-insulating InP or GaAs substrate. The residual strain and indium content in the n-type In0.53Ga0.47As layer have been determined by high-resolution X-ray diffraction, showing nearly zero strain and a fixed indium ratio of 0.53. The deep levels in the layer have been characterized by Deep Level Transient Spectroscopy. The mean value of electron traps at 0.17 ± 0.03 eV below the conduction band minimum EC is assigned to the "localized" states of α 60° misfit dislocations; another broad electron trap with mean activation energies between EC− 0.17 ± 0.01 and 0.39 ± 0.04 eV, is identified as threading dislocation segments with "band-like" states. A high variation of the pre-exponential factor KT by 7 orders of magnitude is found for the latter when changing the filling pulse time, which can be explained by the coexistence of acceptor-like and donor-like states in the core of split dislocations in III-V materials. Furthermore, two hole traps at EV+ 0.42 ± 0.01 and EV+ 0.26 ± 0.13 eV are related to the double acceptor of the Ga(In) vacancy (VGa/In3-/2-) and 60° β misfit dislocations, respectively. Finally, the dislocation climbing mechanism and the evolution of the antisite defects AsGa/In are discussed for n-type In0.53Ga0.47As. [ABSTRACT FROM AUTHOR]

There is a growing interest in using high dose helium implants to alter point defect populations in silicon. Previous reports have shown that the interaction between helium and vacancies leads to the formation of cavities for medium energy (e.g., 20–100 keV) implants. However, the role of certain factors, such as the proximity of the surface, the damage created by the implant, and the effect of the implant temperature, is not well understood for low energy implants. This study explored a new regime of ultralow energy, elevated temperature implants in order to offer an insight into the effect of these parameters. Transmission electron microscopy (TEM) showed that cavity formation was avoided for 0.5 keV, 450 °C implants up to a dose of 8 × 1016 cm−2. However, extended defects in the form of {311} ribbon-like defects and stacking faults were observed. Quantitative TEM showed that the number of interstitials in these defects was less than 0.2% of the implant dose. In addition, thermal helium desorption spectrometry suggested that only 2% of the implanted He dose was retained in interstitial He and HemVn complexes. A first-order dissociation kinetic model was applied to assess desorption from HemVn, which closely matched energies predicted by density functional theory. This population of excess vacancies and excess interstitials was possibly formed because of incomplete Frenkel pair recombination. Raman spectroscopy showed that the stress from the implant was dominated by the stress from the interstitial-type defects. The evolution of the stress and defects was also explored as a function of post-implant annealing. [ABSTRACT FROM AUTHOR]

Compressional and shear wavevelocities of the α phase of hafnium have been measured up to 10.4GPa at room temperature using ultrasonic interferometry in a multi-anvil apparatus. A finite strain equation of state analysis yielded Ks0=110.4(5)GPa,G0= 54.7(5)GPa,K's0 = 3.7,andG'0 = 0.6Ks0 = 110.4(5)GPa,G0= 54.7(5)GPa,Ks0' = 3.7,andG0' = 0.6 for the elastic bulk and shear moduli and their pressure derivatives at ambient conditions. Complementary to the experimental data, the single crystal elastic constants, the elastic anisotropy, and the unit cell axial ratio c/a of α-hafnium at high pressures were investigated by Density Functional Theory(DFT) based first principles calculations. A c/a value of 1.605 is predicted for α-Hf at 40GPa, which is in excellent agreement with previous experimental results. The low-pressure derivative of the shear modulus observed in our experimental data up to 10GPa was found to originate from the elastic constant C44, which exhibits negligible pressure dependence within the current experimental pressure range. At higher pressures (>10GPa), C44 was predicted to soften and the shear wavevelocity νS trended to decrease with pressure, which can be interpreted as a precursor to the α-ω transition similar to that observed in other group IV elements (titanium and zirconium). The acoustic velocities, the bulk and shear moduli, and the acoustic Debye temperature (θD = 240.1KθD=240.1K) determined from the current experiments were all compared well with those predicted by our theoretical DFT calculations. [ABSTRACT FROM AUTHOR]

We explore the formation of single bilayer Sb(111) ultrathin film (Antimonene) on Bi2Te3 and Sb2Te3 substrates for the first time, which is theoretically predicated to be a robust trivial semiconductor but can be tuned to a 2D TI by reducing the buckling height. From angle-resolved photoemission spectroscopy measurements, the antimonene can be well grown on the two surfaces and shows clear band dispersion. The electronic structure of the antimonene shows similar character on the two surfaces, but due to the interfacial strain effect, the bands of antimonene on Bi2Te3 are flatter than on Sb2Te3, which attributes to Bi2Te3 substrate lattice constants lager than Sb2Te3. At the same time, the charge transfer effect is also observed through core level shift, which influences the band dispersion simultaneously. [ABSTRACT FROM AUTHOR]

Mott proposed that impurity bands in corundum-symmetry Ti2O3 at high temperatures caused a collapse in the bandgap. However, the origin of the impurity bands has not yet been clarified. We examine the local structural properties of metal-to-insulator-transition Ti2O3 using in-situ x-ray absorption fine structure (XAFS) measurements at the Ti K edge in the temperature range from 288 to 739 K. The Ti2O3 powder is synthesized by using a chemical reaction method. X-ray diffraction (XRD) measurements from Ti2O3 with a Rietveld refinement demonstrate a single-phased R-3c symmetry without additional distortion. Extended-XAFS combined with XRD reveals a zigzag patterned Ti position and an anomalous structural disorder in Ti-Ti pairs, accompanied by a bond length expansion of the Ti-Ti pairs along the c-axis for T>450 K. The local structural distortion and disorder of the Ti atoms would induce impurity levels in the band gap between the Ti 3d a1g and egπ bands, resulting in a collapse of the band gap for T>450 K. [ABSTRACT FROM AUTHOR]

Mott proposed that impurity bands in corundum-symmetry Ti2O3 at high temperatures caused a collapse in the bandgap. However, the origin of the impurity bands has not yet been clarified. We examine the local structural properties of metal-to-insulator-transition Ti2O3 using in-situ x-ray absorption fine structure (XAFS) measurements at the Ti K edge in the temperature range from 288 to 739 K. The Ti2O3 powder is synthesized by using a chemical reaction method. X-ray diffraction (XRD) measurements from Ti2O3 with a Rietveld refinement demonstrate a single-phased R-3c symmetry without additional distortion. Extended-XAFS combined with XRD reveals a zigzag patterned Ti position and an anomalous structural disorder in Ti-Ti pairs, accompanied by a bond length expansion of the Ti-Ti pairs along the c-axis for T>450 K. The local structural distortion and disorder of the Ti atoms would induce impurity levels in the band gap between the Ti 3d a1g and egπ bands, resulting in a collapse of the band gap for T>450 K. [ABSTRACT FROM AUTHOR]

Electrical properties of metal-semiconductor (M/SC) and metal/oxide/SC structures built with Zr or ZrO2 deposited on oxygen-terminated surfaces of (001)-oriented diamond films, comprised of a stack of lightly p-doped diamond on a heavily doped layer itself homoepitaxially grown on an Ib substrate, are investigated experimentally and compared to different models. In Schottky barrier diodes, the interfacial oxide layer evidenced by high resolution transmission electron microscopy and electron energy losses spectroscopy before and after annealing, and barrier height inhomogeneities accounts for the measured electrical characteristics until flat bands are reached, in accordance with a model which generalizes that by Tung [Phys. Rev. B 45, 13509 (1992)] and permits to extract physically meaningful parameters of the three kinds of interface: (a) unannealed ones, (b) annealed at 350 °C, (c) annealed at 450 °C with the characteristic barrier heights of 2.2-2.5V in case (a) while as low as 0.96V in case (c). Possible models of potential barriers for several metals deposited on well defined oxygen-terminated diamond surfaces are discussed and compared to experimental data. It is concluded that interface dipoles of several kinds present at these compound interfaces and their chemical evolution due to annealing are the suitable ingredients that are able to account for the Mott-Schottky behavior when the effect of the metal work function is ignored, and to justify the reverted slope observed regarding metal work function, in contrast to the trend always reported for all other metal-semiconductor interfaces. [ABSTRACT FROM AUTHOR]

Significant reliability concerns in multiple industries are related to metal whiskers, which are random high aspect ratiofilaments growing on metal surfaces and causing shorts in electronic packages. We derive a closed form expression for the probabilistic distribution of metal whisker lengths. Our consideration is based on the electrostatic theory of metal whiskers, according to which whisker growth is interrupted when its tip enters a random local "dead region" of a weak electric field. Here, we use the approximation neglecting the possibility of thermally activated escapes from the "dead regions," which is later justified. We predict a one-parameter distribution with a peak at a length that depends on the metal surface charge density and surface tension. In the intermediate range, it fits well the log-normal distribution used in the experimental studies, although it decays more rapidly in the range of very long whiskers. In addition, our theory quantitatively explains how the typical whisker concentration is much lower than that of surface grains. Finally, it predicts the stop-and-go phenomenon for some of the whiskers growth. [ABSTRACT FROM AUTHOR]

Transition metal-fullerenes complexes with metal atoms bound on the external surface of C60 are promising building blocks for next-generation fuel cells and catalysts. Yet, at variance with endohedralM@C60, they have received a limited attention. By resorting to first principles simulations, we elucidate structural and electronic properties for the Pd-C60, Pt-C60, PtPd-C60, Pd2-C60, and Pt2-C60 complexes. The most stable structures feature the metal atom located above a high electron density site, namely, the π bond between two adjacent hexagons (π-66 bond). When two metal atoms are added, the most stable configuration is those in which metal atoms still stand on π-66 bonds but tends to clusterize. The electronic structure, rationalized in terms of localized Wannier functions, provides a clear picture of the underlying interactions responsible for the stability or instability of the complexes, showing a strict relationship between structure and electronic gap. [ABSTRACT FROM AUTHOR]

Extensive first principles calculations are carried out to investigate Au monomers and dimers supported on α-Fe2O3(0001) surfaces in terms of structure optimizations, electronic structure analyses, and ab initio thermodynamics calculations of surface phase diagrams. All computations rely on density functional theory in the generalized gradient approximation (Perdew-Burke-Ernzerhof (PBE)) and account for on-site Coulomb interactions via inclusion of a Hubbard correction (PBE+U). The relative stability of Au monomers/dimers on the stoichiometric termination of α-Fe2O3(0001) decorated with various vacancies (multiple oxygen vacancies, iron vacancy, and mixed iron-oxygen vacancies) has been computed as a function of the oxygen chemical potential. The charge rearrangement induced by Au at the oxide contact is analyzed in detail and discussed. On one hand, ab initio thermodynamics predicts that under O-rich conditions, structures obtained by replacing a surface Fe atom with a Au atom are thermodynamically stable over a wide range of temperatures. On the other hand, the complex of a CO molecule on a Au atom substituting surface Fe atoms is thermodynamically stable only in a much more narrow range of values of the O chemical potential under O-rich conditions. In the case of a Au dimer, under O-rich conditions, supported Au atoms at an O-Fe di-vacancy are more stable. However, upon CO adsorption, the complex of a CO molecule and 2 Au atoms located at a single Fe vacancy is more favorable. [ABSTRACT FROM AUTHOR]

The fabrication and electrical characterization of Schottky junction diodes have been extensively researched for three-quarters of a century since the original work of Schottky in 1938. This study breaks from the highly standardized regime of such research and provides an alternative methodology that prompts novel, more efficient applications of the adroit Schottky junction in areas such as chemical and thermal sensing. The core departure from standard Schottky diode configuration is that the metal electrode is of comparable or higher resistance than the underlying semiconductor. Further, complete electrical characterization is accomplished through recording four-probe resistance-temperature (RD-T) characteristics of the device, where electrical sourcing and sensing is done only via the metal electrode and not directly through the semiconductor. Importantly, this results in probing a nominally unbiased junction while eliminating the need for an Ohmic contact to the semiconductor. The characteristic RD-T plot shows two distinct regions of high (metal) and low (semiconductor) resistances at low and high temperatures, respectively, connected by a crossover region of width, ΔT, within which there is a large negative temperature coefficient of resistance. The RD-T characteristic is highly sensitive to the Schottky barrier height; consequently, at a fixed temperature, RD responds appreciably to small changes in barrier height such as that induced by absorption of a chemical species (e.g., H2) at the interface. A theoretical model is developed to simulate the RD-T data and applied to Pd/p-Si and Pt/p-Si Schottky diodes with a range of metal electrode resistance. The analysis gives near-perfect fits to the experimental RD-T characteristics, yielding the junction properties as fit parameters. The modelling not only helps elucidate the underlying physics but also helps to comprehend the parameter space essential for the discussed applications. Although the primary regime of application is limited to a relatively narrow range (ΔT) for a given type of diode, the alternative methodology is of universal applicability to all metal-semiconductor combinations forming Schottky contacts. [ABSTRACT FROM AUTHOR]

The Na content of (Ag,Cu)(In,Ga)Se2 films was cyclically adjusted using a novel method involving cycles of water rinsing at 60 °C followed by heating in air at 200 °C to remove Na and evaporation of NaF to re-introduce Na back into the film. The low temperatures and short heating times ensure that Na is removed only from grain boundaries while leaving grain interiors unaffected. Crossgrain conductivity and Seebeck coefficient were measured during this removal procedure and both measurements decreased when Na was removed and both recovered upon the re-addition of Na, consistent with an increase in compensating donor defects in the absence of Na. These results demonstrate that Na reversibly affects the electrical properties of grain boundaries. We propose that Na reversibly passivates donor-like defects such as InCu double donors at grain boundaries. [ABSTRACT FROM AUTHOR]

We have investigated the structural, bonding, and electronic properties of both ferroelectric (FE) and paraelectric (PE) phases of the hexagonal LuMnO3 compound using calculations based on density functional theory. The structural properties have been determined by employing the generalized gradient approximation with Perdew-Burke-Ernzerhof and Wu-Cohen parameterization. The bonding and electronic properties have been treated by recently developed modified Becke-Johnson exchange potential, which succeeded to open a band gap for both PE and FE phases, in agreement with experimental predictions. The Bader's topological analysis of electronic density showed that the character of the Lu-O axial bonds changes when the crystal exhibits the PE → FE structural transition. This fact is in agreement with experimental findings. The covalent character of the Lu-O bond significantly increases due to orbital hybridization between the Lu 5dz² and O 2pz-states. This bonding mechanism causes the ferroelectricity in the hexagonal LuMnO3 compound. [ABSTRACT FROM AUTHOR]

Consequences of increase in structural fluctuations on heating Pd40Ni10Cu30P20 and Zr46.75Ti8.25Cu75Ni10Be27.5 through their glass to liquid transition range were investigated by measuring the electrical resistivity, p, an electron scattering property. The temperature coefficient of resistivity (TCR = (1/p) dp/dT) of the liquid and glassy states is negative. The plots of their p against T in the Tg (glass to liquid transition) range show a gradual change in the slope similar to the change observed generally for the plots of the density, elastic modulus, and refractive index. As fluctuations in the melt structure involve fewer configurations on cooling, p increases. In the energy landscape description, the melt's structure explores fewer minima with decrease in T, vibrational frequencies increase, and electron scattering and p increase. Plots of (-dp/dT) against T resemble the plot of the specific heat of other glasses and show a sub-Tg feature and a rapid rise at T near Tg. Analysis shows that the magnitude of negative TCR is dominated by change in the phonon characteristics, and configurational fluctuations make it more negative. The TCR of the liquid and glassy states seems qualitatively consistent with the variation in the structure factor in Ziman's model for pure liquid metals as extended by Nagel to metal alloys and used to explain the negative TCR of a two-component metal glass. [ABSTRACT FROM AUTHOR]

One end open VnBzn- (n = 1-5; Bz = benzene) and both ends open VnBzn-1 - (n = 2-5) vanadiumbenzene cluster anions were studied using anion photoelectron spectroscopy and density functional calculations. The smaller (n < 3) VnBzn and VnBzn - 1 clusters and corresponding anions were found to have structural isomers, whereas full-sandwiched VnBzn+1 clusters preferred to form multipledecker sandwich structures. Several isomeric V2Bz2 structures were identified theoretically and the anion photoelectron spectra of V2Bz20/-- were explained well by the coexistence of two isomeric structures: (1) a V2-core structure sandwiched between benzene molecules and (2) an alternating sandwich structure with the spin state strongly dependent on the structure. The adiabatic electron affinity of both VnBzn and VnBzn-1 was found to increase with the cluster size at larger sizes (n = 4 or 5) and approaches to that of VnBzn+1. The evolution of the structural and electronic properties of VnBzm and VnBzm- (m = n and n - 1) with size is discussed in comparison with VnBzn+1 and VnBzn+1-. [ABSTRACT FROM AUTHOR]

Properties of metallic materials are intrinsically determined by their electron behavior. However, relevant theoretical treatment involving quantum mechanics is complicated and difficult to be applied in materials design. Electron work function (EWF) has been demonstrated to be a simple but fundamental parameter which well correlates properties of materials with their electron behavior and could thus be used to predict material properties from the aspect of electron activities in a relatively easy manner. In this article, we propose a method to extract the electron work functions of binary solid solutions or alloys from their phase diagrams and use this simple approach to predict their mechanical strength and surface properties, such as adhesion. Two alloys, Fe-Ni and Cu-Zn, are used as samples for the study. EWFs extracted from phase diagrams show same trends as experimentally observed ones, based on which hardness and surface adhesive force of the alloys are predicted. This new methodology provides an alternative approach to predict material properties based on the work function, which is extractable from the phase diagram. This work may also help maximize the power of phase diagram for materials design and development. [ABSTRACT FROM AUTHOR]

Electrical properties of Schottky contacts on n-type GaN grown in nitrogen rich atmosphere with different N/Ga ratios by hydride vapor phase epitaxy were investigated. We show that tunneling of electrons from the conduction band of GaN to the metal is dominant in our samples. The quality of Schottky contacts does not only depend on surface preparation but also on the growth conditions of the crystals. Schottky contacts on these crystals show an increasing deterioration when higher N/Ga growth ratios are used. We correlate our results with the presence of negatively charged gallium vacancies in the samples. These charges compensate the positively charged donors and lead to a significant increase in series resistance [ABSTRACT FROM AUTHOR]

The influence of graphene interlayers on electronic interface properties of cobalt phthalocyanine on Ni(111) is studied using both photoemission and X-ray absorption spectroscopy. A charge transfer associated with a redistribution of the d-electrons at the Co-atom of the phthalocyanine occurs at the interface to Ni(111). Even a graphene buffer layer cannot prevent the charge transfer at the interface to Ni(111); however, the detailed electronic situation is different. [ABSTRACT FROM AUTHOR]

Photoelectron spectroscopy and density-functional theory are combined to investigate the electronic and structural properties of a series of B-Au alloy clusters: B6Aun- and B6Aun (n = 1-3). Rich spectral features are observed for each species, and vibrational structures are resolved for numerous detachment transitions of B6Au- and B6Au2-. Electron affinities of B6Aun (n = 1-3) are evaluated to be 2.70 ± 0.03, 2.91 ± 0.02, and 3.21 ± 0.05 eV, respectively. Global structural searches are performed for both the anions and their neutrals. The calculated electronic binding energies are compared with experimental measurements to establish the anion global-minimum structures and their corresponding neutral states. The ground-state structures of these clusters are shown to be planar or quasi-planar with an elongated B6 core, to which the first and second Au atoms are bonded terminally and the third Au in a bridging position. All three anion clusters are π antiaromatic. Natural bond orbital analyses show that the B-Au bonding is highly covalent, providing new examples for the Au/H analogy in Au alloy clusters. [ABSTRACT FROM AUTHOR]

The paper presents the fabrication procedure, microstructure and dielectric properties of the low temperature cofired ceramics (LTCC) based on Zn 2 SiO 4 doped with AlF 3 , CaB 4 O 7 , Li 2 TiO 3 and MgTiO 3. The heating microscope studies and differential thermal analysis were used for characterization of the behavior of the green tapes and ceramic samples during heating up to high temperatures. The microstructure and composition were analyzed by scanning electron microscopy, X-ray energy dispersive spectroscopy and XRD method. The dielectric properties were investigated in three frequency regions: 100 Hz–2 MHz, 90–140 GHz and 0.15–3 THz. The developed materials are promising candidates for the LTCC submillimeter wave applications due to a low sintering temperature of 900–980 °C, good compatibility with silver pastes and good dielectric properties – a low dielectric permittivity of 6–6.8, a relatively low dissipation factor of 0.005–0.008 at 1 THz, and a weak temperature dependence of dielectric permittivity. [ABSTRACT FROM AUTHOR]

The Ba 2-x Ca x MgTi 5 O 13 (0 ≤ x ≤ 0.3) microwave dielectric ceramics were for the first time prepared via a conventional solid-state reaction method. A small amount of Ca2+ can dissolve into the lattice by forming solid solutions with a monoclinic structure (C2/m) and further influence the sintering behavior, grain growth and microwave dielectric properties of Ba 2-x Ca x MgTi 5 O 13 ceramics. Both increase of ε r and decrease of Qxf with x should be associated with increased lattice distortion and uneven grain growth although the sample density and the ratio of the ionic polarizability to the molar volume show little variation. Moreover, the A-site bond valence and τ f indicate a close relation in current study, such that the Ca2+substitution can induce an increase of τ f values. The optimum microwave dielectric properties of ε r ∼ 29.3, Qxf ∼ 30,870 GHz (6.5 GHz), and a near-zero τ f ∼ +2.1 ppm/°C can be contained in the x = 0.15 ceramic sintered at 1160 °C. [ABSTRACT FROM AUTHOR]

Bi 3 B 5+ x O 12+3 x /2 (x = 0∼6) compounds were fabricated by a conventional solid-state reaction method. The microwave dielectric properties, sintering behaviour, crystal structure, and phase evolution of the ceramics were investigated. All samples densified at ultra-low temperatures (575∼700 °C). As x increased, the phase composition of the ceramics gradually changed from mixed Bi 4 B 2 O 9 and Bi 3 B 5 O 12 phases to a single Bi 6 B 10 O 24 phase. The ceramic with x = 4 exhibited the best microwave dielectric properties of ε r = 12.14, Q × f = 14,800 GHz, and τ ƒ = −72 ppm/°C at 625 °C. The microwave dielectric properties deteriorated as x increased further. Moreover, the ceramics were proven to cofire with Al and Ag, indicating that they are candidates for ultra-low-temperature cofired ceramic devices. [ABSTRACT FROM AUTHOR]

Lanthanum doped strontium titanate is a potential n-type thermoelectric material at moderate and high temperatures. (La 0.12 Sr 0.88) 0.95 TiO 3 ceramics were prepared by two different routes, conventional sintering at 1500 °C and spark plasma sintering at temperatures between 925 and 1200 °C. Samples with grain size between 40 nm and 1.4 μm were prepared and characterized with respect to their thermoelectric transport properties at temperatures between 100 and 900 °C under reducing conditions (H 2 /H 2 O-buffer mixtures). The thermal conductivity was significantly reduced with decreasing grain size reaching a value of 1.3 W m−1. K−1 at 600 °C for grain size of 40 nm and porosity of 19%. Electrical conductivity increased with increasing grain size showing a maximum of 500 S cm−1 at 200 °C for a grain size of 1.4 μm. The highest figure-of-merit (zT) was measured for samples with 1.4 μm average grain size reaching 0.2 at 500 °C. [ABSTRACT FROM AUTHOR]

The work presents the investigations of Li 1.3 Al 0.3 Ti 1.7 (PO 4) 3 - x LiF Li-ion conducting ceramics with 0 ≤ x ≤ 0.3 by means of X-ray diffractometry (XRD), 7Li, 19F, 27Al and 31P Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) spectroscopy, thermogravimetry (TG), scanning electron microscopy (SEM), impedance spectroscopy (IS) and density method. It has been shown that the total ionic conductivity of both as-prepared and ceramic Li 1.3 Al 0.3 Ti 1.7 (PO 4) 3 is low due to a grain boundary phase exhibiting high electrical resistance. This phase consists mainly of berlinite crystalline phase as well as some amorphous phase containing Al3+ ions. The electrically resistant phases of the grain boundary decompose during sintering with LiF additive. The processes leading to microstructure changes and their effect on the ionic properties of the materials are discussed in the frame of the brick layer model (BLM). The highest total ionic conductivity at room temperature was measured for LATP-0.1LiF ceramic sintered at 800 °C and was equal to σ tot = 1.1 × 10−4 S cm−1. [ABSTRACT FROM AUTHOR]

Defect engineering is applied to induce controllable changes in structures and dielectric behaviors in oxides. SrTiO 3 ceramics modified by complex ions (Nb, Zn)x+ (x = 2, 3, 4 and 5) with variable valence states are prepared by standard solid state method. Phase structures, microstructures, defect structures and dielectric properties of the (Nb, Zn) co-doped SrTiO 3 ceramics have been systematically investigated. In acceptor co-doping, M2 ceramics (x = 2) exhibits extremely low dielectric loss (≤0.001). M3 ceramics (x = 3) shows low conductivity and excellent thermal stability. In equivalent co-doping, M4 ceramics (x = 4) possesses giant permittivity and low dielectric loss. In donor co-doping, M5 ceramics (x = 5) presents improved permittivity while deteriorated dielectric loss. Further investigations reveal that oxygen vacancy is beneficial to the localization of charge carriers and then the low tangent loss, while excess electrons not only contribute to the improved permittivity but also result in high dielectric loss. Appropriate concentrations of oxygen vacancy and electron are significantly important for the formation of multiple defect dipoles or defect clusters, and therefore the greatly modified dielectric properties. The findings may facilitate the ability to engineer the advanced electronic materials. [ABSTRACT FROM AUTHOR]

This study reports the sintering mechanisms of SiO 2 and the relationship between structure, dielectric properties and processing of 1 - x S i O 2 - x P T F E composites with volume fractions up to x = 0.25, prepared by the cold sintering process (270 °C, 430 MPa, 60 min). The importance of transient liquids was evaluated by using TEOS and 5 M NaOH and the densification behavior was investigated by using a semiautomated uniaxial press equipped with a dilatometer. The shrinkage behavior observed when 5 M NaOH was used highlighted the kinetics of nucleation and growth during the phase transition from amorphous silica to α-quartz. Dielectric properties (ε' and tan δ) of cold sintered composites were studied at frequencies between 10−1 Hz and 107 Hz. For composites cold sintered with 5 M NaOH, investigations allowed to confirm the presence of PTFE polymer at the interface between two α-quartz grains by STEM EDS analysis and the presence of a dielectric relaxation at 103-104 Hz. [ABSTRACT FROM AUTHOR]

Sr 3 (Ti 1- x Sn x) 2 O 7 (x = 0–1.0) ceramics were prepared via a standard solid-state reaction method. X-ray diffraction patterns and Rietveld refinement results indicated a composition induced onset of octahedral tilting when x > 0.2, and the crystal structure transformed in sequence: tetragonal (I 4/ mmm) → coexistence of tetragonal and orthorhombic (I 4/ mmm + Amam) → orthorhombic (Amam). The τ f value could be successfully tuned towards zero and the effects of octahedral tilting on the evolution of τ f value were emphasized. Meanwhile, the role of tolerance factor in tailoring the resultant τ ε of the present ceramics was revealed and compared with the empirical rule for complex perovskites. Qf value decreased monotonously with increasing x , which could be elucidated by the variations of extrinsic parameters and intrinsic dielectric loss extrapolated from the infrared reflectivity spectra. The optimum microwave dielectric properties were achieved at x = 0.8 (ε r = 18.6, Qf = 45,250 GHz, τ f =–14 ppm/oC). [ABSTRACT FROM AUTHOR]

Ti-doped CoSb 3 thin films were prepared through layer inter-diffusion method and the prepared thin films have unique architecture, containing nano-size grains. According to the Raman analysis, the films have weaker atomic vibration after Ti doping. This nano-structure and the weak atomic vibration can scatter a wide-range spectrum of phonons, resulting the significantly decrease of thermal conductivity. In addition, this material design also leads to a very important improvement of the absolute Seeback coefficient value, which increases from about 50 μVK−1 to over 100 μVK-1. As the result, the maximum ZT value is 0.86 at 523 K for a Ti doped sample, which is six times higher than the un-doped sample and is comparable to the best value for the CoSb 3 based thin films. A flexible CoSb 3 based thin film thermoelectric generator was also fabricated and shows that the response time of all the touch events is below 1 s. [ABSTRACT FROM AUTHOR]

Transition metal phthalocyanines (MPc's) are an interesting class of material, and their magnetic and electronic properties are determined by the orbital occupation of the transition metal 3d orbitals incorporated in the molecules center. Thus, the ground state configuration of the transition metal center is very important for a complete understanding of these materials. We present experimental data taken using x-ray absorption and x-ray photoemission spectroscopy together with a theoretical interpretation of MPc series with M=Zn, Cu, Ni, Co, Fe, and Mn. The combination of these methods allows us to narrow down possible dominating ground state configurations and shed a brighter light on the electronic structure of these complexes. [ABSTRACT FROM AUTHOR]

We report on the electronic properties of Fe and Cr in n-type germanium studied using conventional and Laplace Deep Level Transient Spectroscopy techniques (LDLTS). Using Schottky barriers restricts the studies to levels located in the upper half of the band gap. However, by applying external optical excitation to generate minority carriers, the investigation is extended to the lower half of the band gap. Major findings already published by other authors are in several cases confirmed. However, new insight is revealed on the microscopic behavior of these two chemical species such as their interactions with hydrogen giving rise to the generation of complex-related levels in the band gap. For the Fe case, the small difference in energy of its two levels raises the question as to the possibility of negative-U character. [ABSTRACT FROM AUTHOR]

Hybrid functionals often exhibit a marked improvement over semi-local functionals in the description of the electronic structure of organic materials. Because short-range hybrid functionals, notably the Heyd-Scuseria-Ernzerhof (HSE) functional, can also describe the electronic structure of metals reasonably well, it is interesting to examine to which extent they can correctly describe the electronic structure at metal-organic interfaces. Here, we address this question by comparing HSE calculations with many-body perturbation theory calculations in the GW approximation, or with experimental photoemission data, for two prototypical systems: benzene on graphite and benzene diamine on gold. For both cases, we find that while HSE yields results that are somewhat closer to experiment than those of semi-local functionals, the HSE prediction is still lacking quantitatively by ∼1 eV. We show that this quantitative failure arises because HSE does not correctly capture the fundamental gap of the organic or its renormalization by the metal. These discrepancies are traced back to missing long-range exchange and correlation components, an explanation which applies to any conventional or short-range hybrid functional. [ABSTRACT FROM AUTHOR]

The influence of stress migration (SM) on the electromigration (EM) reliability is studied here for very fine line interconnects, fabricated using the 45-nm Cu/low-κ interconnect process flow. As opposed to the current understanding that SM is not a concern for the narrow metal lines because of limited availability of vacancies for voiding, we found that SM does have serious wear-out effects. The EM lifetime distribution was severely degraded by around 38% for the samples that had been subjected to a 1000-h SM-only test, with a drastic reduction in the slope of the EM lognormal fitting distribution, from 0.548 to 0.193. The current density exponent of Black's equation for SM+EM stressed samples is ∼1, suggesting that void had already been nucleated because of the SM-only test. The high intrinsic tensile stress in the line is suspected to be responsible for this early void nucleation. In the second part, we developed a Monte Carlo simulation model to estimate the void nucleation and growth time using the EM-only and SM+EM degradation tests. We found that at low percentile failures overall failure time is mainly growth dominated, whereas at high percentile failures overall failure time is nucleation dominated. Stress migration was found to shorten the nucleation time for all the samples. [ABSTRACT FROM AUTHOR]

We have employed first-principles density-functional calculations to study the electronic characteristics of covalently functionalized graphene by metal-bis-arene chemistry. It is shown that functionalization with M-bis-arene (M = Ti, V, Cr, Mn, Fe) molecules leads to an opening in the bandgap of graphene (up to 0.81 eV for the Cr derivative), and as a result, transforms it from a semimetal to a semiconductor. The bandgap induced by attachment of a metal atom topped by a benzene ring is attributed to modification of π-conjugation and depends on the concentration of functionalizing molecules. This approach offers a means of tailoring the band structure of graphene and potentially its applications for future electronic devices. [ABSTRACT FROM AUTHOR]

Early transition metal dichalcogenides (TMDC), characterized by their quasi-two-dimensional layered structure, have attracted intensive interest due to their versatile chemical and physical properties, but a comprehensive understanding of their structural and electronic properties from a first-principles point of view is still lacking. In this work, four simple TMDC materials, MX2 (M = Zr and Hf, X = S and Se), are investigated by the Kohn-Sham density functional theory (KS-DFT) with different local or semilocal exchange-correlation (xc) functionals and many-body perturbation theory in the GW approximation. Although the widely used Perdew-Burke-Ernzelhof (PBE) generalized gradient approximation (GGA) xc functional overestimates the interlayer distance dramatically, two newly developed GGA functionals, PBE-for-solids (PBEsol) and Wu-Cohen 2006 (WC06), can reproduce experimental crystal structures of these TMDC materials very well. The GW method, currently the most accurate first-principles approach for electronic band structures of extended systems, gives the fundamental band gaps of all these materials in good agreement with the experimental values obtained from optical absorption. The minimal direct gaps from GW are systematically larger than those measured from thermoreflectance by about 0.1-0.3 eV, implying that excitonic effects may be stronger than previously estimated. The calculated density of states from GW quasi-particle band energies agrees very well with photo-emission spectroscopy data. Ionization potentials of these materials are also computed by combining PBE calculations based on the slab model and GW quasi-particle corrections. The calculated absolute band energies with respect to the vacuum level indicate that that ZrS2 and HfS2, although having suitable band gaps for visible light absorption, cannot be used for overall water splitting as a result of mismatch of the conduction band minimum with the redox potential of H+/H2. [ABSTRACT FROM AUTHOR]

We report the structure and spectroscopic characteristics for the Xe:HI van der Waals binary isomers determined from variational solutions of two-dimensional and three-dimensional (3D) vibrational Schrödinger equations. The solutions are based on a potential energy surface computed at the coupled-cluster level of theory including single and double excitations and a non-iterative perturbation treatment of triple excitations [CCSD(T)]. The dipole moment surface was calculated using quadratic configuration interaction (QCISD). The global potential minimum is shown to be located at the anti-hydrogen-bonded Xe-IH isomer, 21 cm-1 below the secondary local minimum associated with the hydrogen-bonded Xe-HI isomeric form. The dissociation energy from the global minimum is 245.9 cm-1. 3D Schrödinger equations are solved for the rotational quantum numbers J = k = 0, 1, and 2, without invoking an adiabatic separation of high- and low-frequency degrees of freedom. The vibrational ground state resides in the Xe-HI potential well, while the first excited state, 8.59 cm-1 above the ground, occupies the Xe-IH well. We find that intra-complex dynamics exhibits a sudden transformation upon increase of the r(HI) bond length, accompanied by abrupt changes in the geometric and dipole parameters. A similar chaotic behavior is predicted to occur for Xe:DI at a shorter r(DI) bond length, which implies stronger coupling between low- and high-frequency motions in the heavier complex. Our calculations confirm a strong enhancement for the r(HI) stretch fundamental and a significant weakening for the first overtone vibrational transitions in Xe:HI, as compared to those in the free HI molecule. A qualitative explanation of this, earlier experimentally detected effect is suggested. [ABSTRACT FROM AUTHOR]

The effect of geometrical irregularities in the work function and emitting properties of metallic surfaces at low potentials is studied. For this purpose, we propose a simplified model consisting of rectangular fractures and a classical formalism for the work function determination. The dependence of the work function with the fractures size is determined by using the electrostatic image potential method. The emission current density properties when an external electric field is applied are also analyzed. [ABSTRACT FROM AUTHOR]

The P(5) branch features of the A 3[uppercase_phi_synonym]4←X 3[uppercase_phi_synonym]4 (1,0) band near 628.2 nm of a molecular beam of iridium monofluoride, 193IrF, were recorded field free and in the presence of a static electric field. The 193Ir (I1=3/2) and 19F (I2=1/2) hyperfine interactions in the A 3[uppercase_phi_synonym]4 (υ=1) and X 3[uppercase_phi_synonym]4 (υ=0) states were analyzed. The permanent electric dipole moments, μvector el, for the A 3[uppercase_phi_synonym]4 (υ=1) and X 3[uppercase_phi_synonym]4 (υ=0) states were determined to be 1.88(5) and 2.82(6) D, respectively, from the analysis of the observed Stark shifts. A comparison of the electric dipole moments for IrC, IrN, and CoF is presented. [ABSTRACT FROM AUTHOR]

Structural and electronic properties of La3+ immersed in bulk water have been assessed by means of density functional theory (DFT)-based Car–Parrinello molecular dynamics (CPMD) simulations. Correct structural properties, i.e., La(III)-water distances and La(III) coordination number, can be obtained within the framework of Car–Parrinello simulations providing that both the La pseudopotential and conditions of the dynamics (fictitious mass and time step) are carefully set up. DFT-MD explicitly treats electronic densities and is shown here to provide a theoretical justification to the necessity of including polarization when studying highly charged cations such as lanthanoids(III) with classical MD. La3+ was found to strongly polarize the water molecules located in the first shell, giving rise to dipole moments about 0.5 D larger than those of bulk water molecules. Finally, analyzing Kohn–Sham orbitals, we found La3+ empty 4f orbitals extremely compact and to a great extent uncoupled from the water conduction band, while the 5d empty orbitals exhibit mixing with unoccupied states of water. [ABSTRACT FROM AUTHOR]

Structural and electronic properties of La3+ immersed in bulk water have been assessed by means of density functional theory (DFT)-based Car–Parrinello molecular dynamics (CPMD) simulations. Correct structural properties, i.e., La(III)-water distances and La(III) coordination number, can be obtained within the framework of Car–Parrinello simulations providing that both the La pseudopotential and conditions of the dynamics (fictitious mass and time step) are carefully set up. DFT-MD explicitly treats electronic densities and is shown here to provide a theoretical justification to the necessity of including polarization when studying highly charged cations such as lanthanoids(III) with classical MD. La3+ was found to strongly polarize the water molecules located in the first shell, giving rise to dipole moments about 0.5 D larger than those of bulk water molecules. Finally, analyzing Kohn–Sham orbitals, we found La3+ empty 4f orbitals extremely compact and to a great extent uncoupled from the water conduction band, while the 5d empty orbitals exhibit mixing with unoccupied states of water. [ABSTRACT FROM AUTHOR]

In this study we investigated traps in InSb/SiOx/Metal structure. In particular, emphasis was given to various methods of charging and discharging the interfaces and SiOx layers by thermal-bias-stress. It is shown that the widely used capacitance-voltage profiling is insensitive to trap energies. Thus additional, complementary methods, such as thermally stimulated discharge were adopted and used to deepen the understanding. It is proposed that the traps in the passivation layer are charged by dc leakage current, and that the distribution of trap energies is not uniform. Furthermore, we report here methods that were developed to charge and discharge specific trap levels selectively. [ABSTRACT FROM AUTHOR]

Material and electrical characterizations of sputter-deposited HfxRuy and HfxRuyNz gate electrodes atop atomic layer deposited HfO2 were performed with a focus on optimizing their compositions for suitable applications in p-metal oxide semiconductor field effect transistors (pMOSFETs), since Fermi level pinning is a more severe issue for higher work function metals. The alloys of HfxRuy with effective work functions (EWFs) ranging from 4.4 to 5.0 eV were achieved when the Ru metal ratio was varied from 53% to 74%. Nitrided hafnium ruthenium alloys, HfxRuyNz (0%–25% N), with EWFs of 4.9–5.2 eV were also synthesized. Among these materials, Hf0.26Ru0.74 and Hf0.05Ru0.77N0.18 were determined to have EWFs adequate for pMOSFET devices of 5.0 and 5.2 eV, respectively. The slightly higher than expected EWFs of these metal gates are attributed to the presence of oxygen. The depth profiling of the as-deposited gate stacks showed reasonably sharp interfaces between the gate electrode and the gate dielectric with the HfxRuy alloy exhibiting better interfacial properties. Upon annealing, the HfxRuy alloys were found to be more stable than the HfxRuyNz alloys on HfO2. [ABSTRACT FROM AUTHOR]

Using state-of-the-art first-principles calculations, we study the properties of the ferromagnetic Heusler compounds NiYSi, where Y stands for V, Cr, or Mn. NiCrSi and NiMnSi contrary to NiVSi are half-metallic at their equilibrium lattice constant exhibiting integer values of the total spin magnetic moment, and thus we concentrate on these two alloys. The minority-spin gap has the same characteristics as for the well-known NiMnSb alloy being around ∼1 eV. Upon tetragonalization, the gap is present in the density of states even for expansion or contraction of the out-of-plane lattice parameter by 5%. The Cr–Cr and Mn–Mn interactions make ferromagnetism extremely stable and the Curie temperature exceeds 1000 K for NiMnSi. Surface and interfaces with GaP, ZnS, and Si semiconductors are not half-metallic but, in the case of NiCrSi, the Ni-based contacts present spin polarization at the Fermi level around 90%. Finally, we show that there are two cases of defects and atomic-swaps. The first ones, which involve the Cr(Mn) and Si atoms, induce states at the edges of the gap, which persists for a moderate concentration of defects. Defects involving Ni atoms induce states localized within the gap completely destroying the half-metallicity. Based on single-impurity calculations, we associate these states to the symmetry of the crystal. [ABSTRACT FROM AUTHOR]

Recent experiments have demonstrated ambipolar channel conduction and light emission in conjugated polymer field-effect transistors (FETs). The devices have source/drain contacts fabricated using metals with different work functions. Negative charge carriers are injected from a low work-function metal contact and positive charge carriers from a high work-function contact. In the ambipolar mode of operation, the gate potential lies between the potentials of the electron and hole injecting contacts, so that electrons dominate the channel conductance near the electron injecting contact and holes dominate channel conductance near the hole injecting contact. The injected charge carriers propagate along the FET channel and recombine in regions where both types of carriers are present. The location and intensity of maximum recombination and light emission is controlled by the voltages applied to the transistor terminals. In this paper a device model for ambipolar organic field-effect transistors based on the gradual channel approximation is presented. The model includes the effect of charge carrier trapping through density dependent mobilities. The resulting nonlinear differential equation for the channel potential is solved numerically. The results of the device model are in good agreement with the published experimental data. [ABSTRACT FROM AUTHOR]

We studied the oxide charges and traps within nitrided Hf-silicate (HfSiON)/SiO2 gate stacks processed with high-temperature annealing with a spectroscopic technique by using high spatial resolution scanning capacitance microscopy. Spectroscopy was performed by detecting the static capacitance (dC/dZ) between a conductive probe and the sample while sweeping the sample bias. The dC/dZ image and spatially resolved dC/dZ-V spectrum revealed the existence of positive fixed charges within HfSiON and interface trap charges between the SiO2 underlayer and Si substrate. We also observed a transient electron trap process from the conductive probe to the HfSiON film as abrupt discontinuities in the dC/dZ-V spectrum and with bias-induced topography change of the HfSiON surface. These oxide charges and trap sites distribute inhomogeneously within HfSiON/SiO2 gate stacks, and the origin of these charged defects is ascribable to phase separation induced by high-temperature postdeposition annealing. [ABSTRACT FROM AUTHOR]

We have studied the electronic structure of potassium-doped copper phthalocyanine (CuPc) using photoemission spectroscopy. A detailed analysis of the core-level spectra allows us to propose possible lattice sites for the potassium ions. None of the films prepared in our studies showed a finite electronic density of states at the Fermi level (EF), which is in contrast to reports in the literature. Possible reasons for this discrepancy are discussed. [ABSTRACT FROM AUTHOR]

Metal-ferroelectric–insulator-semiconductor device structures with ferroelectric vinylidene fluoride-trifluoroethylene copolymer and SiO2 buffer layer integrated gate stack over n-Si are formed, and their potential for fabricating polymeric nonvolatile random access memory devices is demonstrated. Capacitance-voltage (C–V) studies show that switchable polarization in poled polyvinylidene fluoride PVDF copolymer film changes the Si-surface potential and causes modulation of the Si-surface conductance. The (C–V) hysteresis and bidirectional flatband voltage shift at -10 to +6 V, depending on the polarization field direction and remnant polarization at the ferroelectric PVDF copolymer gate, presents a memory window. The space charge at n-Si and switchable polarization both reduce the field across the ferroelectric PVDF. The observed asymmetry of the negative flatband-voltage shifts in the negatively poled ferroelectric polymer state is the result of the depletion layer formation, which reduces the field across the polymeric gate. Internal field due to negative and positive bound charges within PVDF copolymer and SiO2, respectively, influences polarization switching by pinning of dipoles. Higher negative gate bias is needed to overcome the pinning effect and to switch the polarization field. @2004 American institute of Physics. [ABSTRACT FROM AUTHOR]

We have fabricated and characterized double-layer-type electroluminescent devices with the structure of indium-tin-oxide-coated glass/poly[2-(N-carbazolyl)-5-(2-ethylhexyloxy)-1, 4-phenylenevinylene] (CzEH-PPV)/tris(8-hydroxyquinoline) aluminum (Alq[sub 3])/Li:Al, in which CzEH-PPV was used as a hole transport medium, and neutral and ionized cluster beam deposition (NCBD and ICBD) methods were applied to deposit Alq[sub 3]. The surface morphology observed by atomic force microscopy shows that NCBD and especially ICBD methods are more efficient in producing flat and smooth thin film surfaces in comparison to the conventional physical vapor deposition method. Studies of photoluminescence, electroluminescence (EL), and device characteristics demonstrate that the polymeric thin film is susceptible to ion radiation damage and the NCBD-based devices show better device performance, including lower threshold and turn-on voltages, improved EL intensity-voltage, current density-voltage, and external quantum efficiency (EQE)-current characteristics. In addition, the doping effect of the highly fluorescent dye molecule 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran into the Alq[sub 3] layer reveals a complete energy transfer, color-tuning capability and enhanced EQEs. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Porous silicon (PS) based metal/PS/p-Si structures with PS layer of different thickness were prepared on moderate- and high-resistivity substrates. Measurements of current–voltage (I–V) characteristics and impedance at various temperatures were used for the investigation of the electrical properties of these structures. Electrical properties of the structures with relatively thin (1 μm) PS layer significantly differ from those of thick structures. The exponential forward bias I–V dependencies for thin structures spread over several orders of magnitude with a low value of quality factor (close to 2) and have activation temperature dependencies with an activation energy equal to half the c-Si band gap. The reverse current has a square root dependence on the reverse bias voltage and the activation energy is equal to half the c-Si band gap. Therefore, it was concluded that the reverse and forward currents in thin PS-based device structures were determined by the generation and recombination of carriers in the depletion region of the c-Si substrate. It was shown that a large area spreading current exists in structures made on highly resistive substrates, which appears to be due to a highly conductive inverse (n-type) layer formed in the p-Si substrate at the PS/p-Si heterojunction. The spreading effect leads to high reverse currents and high capacitance of the device structures made on highly resistive substrates. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]