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Phonon dispersion and thermal conduction properties of hyperbranched nanostructures with unique topological complexity are theoretically and numerically investigated in this research. We present analytical cantilever-in-mass models to analyze and control the inherent resonance hybridization in hyperbranched nanomembranes containing different configurations and cross sections. We show that these local resonances hosted by hyperbranched nanopillars can generate numerous flat bands in the phonon dispersion relation and dramatically lower the group velocities, consequently resulting in a significant reduction of the thermal conductivity. The applicability of the proposed analytical models in thermal conductivity tuning is demonstrated, and a superior performance in reducing the heat flux in nano-structured membranes is exhibited, which can potentially lead to improved thermoelectric energy conversion devices. [ABSTRACT FROM AUTHOR]

Investigates the formation of cobalt-silicon films by the reaction of ternary cobalt/titanium/silicon system. Sequential deposition of cobalt films deposited on silicon substrates by ion beam sputtering; Success of the deposition in the growth of epitaxial single-crystalline cobalt-silicon films on both silicon and silicon substrates; Formation of thin layer of titanium-nitrogen on top of the epitaxial cobalt-silicon.

Presents a study which investigated the electrical transport properties of CoSi[sub2] and Co(Si[subx]Ge[sub1-x])2 films formed by different methods. Properties of the thin films after low temperature annealing; Discussion on the hole carrier density of the samples studied; Characteristic of CoSi[sub2] which made it a desirable material for contact and gate level interconnection of large scale integrated circuits.

Examines the Hall effect data of the bismuth-strontium-calcium-copper-oxygen thin films samples. Information on the thin film samples; Methodology of the study; Results and discussion.

Presents a study which measured the electrical resistivity and Hall effect of TiSi[sub2] thin films. Materials and methods used; Description of the temperature dependence of resistivity of TiSi[sub2] thin film; Overview of the Hall effect of TiSi[sub2] thin film formed on single crystal silicon.

Presents a study that examined the solid state reaction of cobalt-titanium with an epitaxially grown silicon-germanium strained layer. Use of rapid thermal annealing system; Measurement of electrical resistivity and Hall effect of the compound; Background of crystalline silicon-germanium.

Dissipative elastic metamaterials have attracted increased attention in recent times. This paper presents the development of a dissipative elastic metamaterial with multiple Maxwell-type resonators for stress wave attenuation. The mechanism of the dissipation effect on the vibration characteristics is systematically investigated by mass-spring-damper models with single and dual resonators. Based on the parameter optimization, it is revealed that a broadband wave attenuation region (stopping band) can be obtained by properly utilizing interactions from resonant motions and viscoelastic effects of the Maxwell-type oscillators. The relevant numerical verifications are conducted for various cases, and excellent agreement between the numerical and theoretical frequency response functions is shown. The design of this dissipative metamaterial system is further applied for dynamic load mitigation and blast wave attenuation. Moreover, the transient response in the continuum model is designed and analyzed for more robust design. By virtue of the bandgap merging effect induced by the Maxwell-type damper, the transient blast wave can be almost completely suppressed in the low frequency range. A significantly improved performance of the proposed dissipative metamaterials for stress wave mitigation is verified in both time and frequency domains. [ABSTRACT FROM AUTHOR]

The effects of annealing ambient on the structural and transport properties of epitaxial La0.7 Ba0.3MnO3 films suffering large compressive strain on LaAlO3 substrates (LBMO/LAO) have been investigated. Independent of oxygen or argon ambient, a high temperature (900 °C) post-annealing process leads to a c-axis contraction, which can be attributed to the oxygen transfer from the in-plane to the out-of-plane direction. Meanwhile, the transport properties are similar with each other for both the Ar-annealed and O2-annealed films. The comparison of the ambient annealing effects between the highly strained LBMO/LAO films and negligibly strained LBMO films on SrTiO3 substrates indicates that a large in-plane compressive strain favors decreasing oxygen deficiency in the films, especially in the ab-plane. [ABSTRACT FROM AUTHOR]

The photorefractive properties of nominally pure near-stoichiometric LiNbO[sub 3] crystals grown from congruent melts containing 11 mol % K[sub 2]O are studied, and some photorefractive properties which are very different from those in congruent LiNbO[sub 3] crystals are observed. Large stationary energy transfer (Γ[sub max]=25 cm[sup -1]) exists in near-stoichiometric crystals though the photovoltaic field is dominant. The light-induced scattering fanning is markedly asymmetric in the crystals, which is very different from the symmetric fanning observed in congruent ones. Our analysis shows that these differences are caused by the large photovoltaic field and the relatively small density of filled traps in as-grown near-stoichiometric LiNbO[sub 3]. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The low-field dielectric responses of pure and 0.15 wt. % MnO-added (1-x)Pb(Fe2/3W1/3)O3–xPbTiO3 [(1-x)PFW–xPT] were investigated with the empirical model, the Curie–Weiss law and the spin-glass model. According to the experimental data and the fitting results, we conclude that (1) the lattice structure is changed and the electron compensation is induced with MnO addition. (2) The dielectric behaviors obey the Curie–Weiss law as the temperature is much far above Tm for all samples. (3) TCW, the temperature at which the dielectric behaviors deviate from the Curie–Weiss law, is higher and the diffuse phase characteristic is more obvious as decreasing PbTiO3 content or adding MnO. (4) The tailed temperature-dependent local order parameters, which are derived from the spin-glass model and the experimental results, for more diffuse phase transition relaxors show higher thermal stability in the spontaneous polarization microregions. (5) The temperature-dependent local ordering parameters change from a long-range-ordered ferroelectric state to a short-range-ordered relaxor with decreasing the PbTiO3 content or adding MnO. [ABSTRACT FROM AUTHOR]

The magnetocrystalline anisotropy of La0.67Ba0.33MnO3 (LBMO) epitaxial films suffering large compressive strain on LaAlO3 (LAO) substrates (LBMO/LAO) was investigated by ferromagnetic resonance (FMR) in the temperature range between 2 and 320 K. By mapping out the dependence of the FMR position on the angle between the applied magnetic field and crystallographic axes of the films, a large easy-plane anisotropy has been found in such compressive strained LBMO films, which is in contrast to the general tendency presented in strained manganite films. Furthermore, the excellent epitaxial crystallographic orientation due to the LAO substrates gives rise to an appreciable fourfold symmetry of the in-plane anisotropy with easy-axis along the [110] direction. The results are discussed by taking tolerance factor and giant magnetostriction of Ba-doped manganites into account. [ABSTRACT FROM AUTHOR]

Atomic layer deposition (ALD) of TiO2 thin films using Ti isopropoxide and tetrakis-dimethyl-amido titanium (TDMAT) as two kinds of Ti precursors and water as another reactant was investigated. TiO2 films with high purity can be grown in a self-limited ALD growth mode by using either Ti isopropoxide or TDMAT as Ti precursors. Different growth behaviors as a function of deposition temperature were observed. A typical growth rate curve-increased growth rate per cycle (GPC) with increasing temperatures was observed for the TiO2 film deposited by Ti isopropoxide and H2O, while surprisingly high GPC was observed at low temperatures for the TiO2 film deposited by TDMAT and H2O. An energetic model was proposed to explain the different growth behaviors with different precursors. Density functional theory (DFT) calculation was made. The GPC in the low temperature region is determined by the reaction energy barrier. From the experimental results and DFT calculation, we found that the intermediate product stability after the ligand exchange is determined by the desorption behavior, which has a huge effect on the width of the ALD process window. [ABSTRACT FROM AUTHOR]

A thin amorphous Si (α-Si) interlayer is produced between the sputtering deposited ytterbium layer and Si(001) substrate, and the growth of the ytterbium silicide (YbSi2-x) film is investigated in this paper. Formation of YbSi2-x was verified by x-ray diffraction (XRD). The silicide film morphology was examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). SEM results reveal that without the α-Si interlayer, pinholes form during YbSi2-x formation on Si(001). Furthermore, the XRD results demonstrate that there is a strong epitaxial relationship between the formed YbSi2-x and Si(001) substrate, and it is believed to be the reason for the formation of pinholes. To suppress the formation of pinholes, a thin α-Si interlayer with different thicknesses is introduced on the Si(001) substrate prior to Yb film deposition. The α-Si interlayer is produced by either sputter deposition employing a Si target or by Si ion implantation induced amorphization. In the presence of this thin α-Si interlayer, epitaxial growth of YbSi2-x is greatly suppressed even when the α-Si interlayer is so thin that full silicidation of the deposited Yb film still requires consumption of Si atoms from the Si(001) substrate. Fabrication of a pinhole-free YbSi2-x film is also demonstrated by SEM and AFM. The growth mechanism of the pinhole-free YbSi2-x film in the presence of a thin α-Si interlayer is discussed. [ABSTRACT FROM AUTHOR]

Different from the conventional current-voltage and capacitance-voltage methods, Schottky contact barrier height extraction by admittance measurement is proposed and discussed in this paper. In this method, the barrier height can be simply extracted from the difference between the measured admittance at zero bias and a reasonably high forward bias. Both simulation results and experimental data demonstrate that the proposed method is effective not only for extraction of Schottky contacts with higher barrier heights (>0.4 eV) but also for extraction of those with moderately lower barrier heights (0.2–0.4 eV). [ABSTRACT FROM AUTHOR]

The temperature-dependent current-voltage (I-V-T) technique has been used to study the Ni/Si solid phase reaction by measuring the Schottky barrier height (SBH) inhomogeneity of Ni-silicide/ Si Schottky diodes. The experimental results show the strong dependence of SBH inhomogeneity on the Ni/Si solid phase reaction. The SBH distribution of the diodes annealed at 500 and 600 °C can be described by a single-Gaussian function and the diode annealed at 500 °C is found to have the best homogeneity and the smallest leakage current. The SBH distribution of the diodes annealed at 400, 700, and 800 °C can be described by a double-Gaussian function in which the mean value of the second Gaussian function is substantially smaller than that of the dominant Gaussian function. The variation of SBH inhomogeneity, an interface property, is related to the phase evolution process in the Ni/Si solid phase reaction, and verified by reverse I-V measurements. Our results indicate that the I-V-T technique may be developed as a wafer-level testing tool to monitor the silicidation process in the complementary metal-oxide-semiconductor device fabrication. [ABSTRACT FROM AUTHOR]

Epitaxial growth of CoSi[sub 2] by solid state reaction of Co/a-Si/Ti/Si(100) is investigated. A Ti/a-Si composite interlayer is used to modify the diffusion barrier and influence the epitaxial growth process. The epitaxial quality of the CoSi[sub 2] is improved compared to the film grown by Co/Ti/Si reaction. A multielement amorphous layer is formed by a solid-state amorphization reaction at the initial stage of the multilayer reaction. This layer acts as a diffusion barrier, which controls the atomic interdiffusion of Co and Si while limiting the supply of Co atoms. CoSi[sub 2] grows as the first phase and the growth interface of the epitaxial CoSi[sub 2] is at both the CoSi[sub 2]/Si and CoSi[sub 2]/CoSi interfaces. Investigation of the growth kinetics shows that the activation energy of CoSi[sub 2] formation is larger than that without an amorphous Si layer. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Discusses a study which investigates the influence of heat treatment in an oxygen atmosphere on the induced dark traces in lithium niobate (LiNbO[sub3] samples. Information on LiNbO[sub3] crystals; Description of the transmission loss spectra of dark traces in LiNbO[sub3]:magnesium and LiNbO[sub3]:zinc; Factor that causes changes in the valence state of point defects and host ions.

Focuses on visible electroluminescence from semitransparent gold film/extra thin silicon-rich silicon oxide (SiO) film/p-Si diodes at room temperature. Use of the magnetron sputtering technique; Types of luminescence centers in the SiO films; Visible light emitted by electron-hole pairs.

We report the experimental study of hole transport in poly(vinylcarbazole) (PVK) films doped with colloidal CdSe/ZnS core-shell quantum dots (QDs) determined using the Time-of-Flight (TOF) method. The miscibility between PVK and the QDs is improved by capping the QDs with a novel 11-(N-carbazolyl) undecanoic acid (C11) ligand instead of commonly used organic ligands, such as oleic acid. The study of the hole mobility of the pristine and doped PVK films with a doping concentration of the C11 capped QDs ranging from 1.61 × 1017 to 7.10 × 1018 dots/cm3 was performed as a function of electric field and temperature in the range of 105-106 V/cm and 298-338 K, respectively. Upon increasing the QD concentration, a decrease of hole mobility was observed by up to nearly 2 orders in magnitude at a doping concentration of 3.87 × 1018 dots/cm3 at T = 298 K. This suggests that the QDs induce shallow hole traps. The field and temperature dependence of the hole mobility was characterized using the Bässler disorder model and showed an increase of the energetic disorder (σ) from 124 to 204 meV as well as of the spatial disorder (Σ) from 0.95 to 5 when the concentration of the QDs was increased to 3.87 × 1018 dots/cm3. At higher concentration of the QDs (7.10 × 1018 dots/cm3), an increase of the hole mobility was observed suggesting hopping of the holes through the QD clusters. In addition, we also found that for this high doping concentration, the field dependence of the hole mobility was no longer in agreement with the Bässler disorder model. One should consider that at this doping concentration, the volume occupied by the inorganic (CdSe + ZnS) and organic (C11) components of the QDs in the doped film was estimated to be 14.6 and 15.8 volume %, respectively. This implies that the volume fraction of the inorganic material is very close to the percolation threshold, which amounts to 17 volume % for small spherical particles embedded in a three dimensional matrix. Furthermore, the conductivity data suggest a qualitative change in film properties between the samples with 3.87 × 1018 and 7.10 × 1018 dots/cm3. The study of film morphology by atomic force microscopy (AFM) experiment shows that while for the film with 3.87 × 1018 dots/cm3 the surface of the film has still the same features as that of a pristine PVK film, this is no longer the case for the film with 7.10 × 1018 dots/cm3, where shallow holes with a diameter of 100 to 200 nm become visible. These holes with the size much larger than the diameter of an individual QD likely correspond to clusters of the QDs. Upon further increasing the QD concentration to 9.68 × 1018 dots/cm3, the density of these holes is also increased. A correlation between the conductivity data and the film morphologies indicates that the presence of these QD clusters in the sample with 7.10 × 1018 dots/cm3 does not only change the homogeneity and roughness of the film but also leads to a significant change in the shape of the density of states of the energy sites for hopping holes resulting in a field and temperature dependence of the hole mobility that is no longer compatible with the Gaussian disorder model for this sample. Furthermore, the presence of these 'hole' structures observed with AFM might imply a formation of large QD clusters in the polymer film, which form continuous pathways for charge carrier hopping between the opposite electrodes. [ABSTRACT FROM AUTHOR]