Electrical Properties of Nanocomposites
TL;DR: In this article, the state-of-the-art for synthesizing composites of nanometer-sized phases (metal, semiconductor or ceramic) dispersed in a matrix has been reviewed.
Abstract: The present state-of-the-art for synthesizing composites of nanometer-sized phases (metal, semiconductor or ceramic) dispersed in a matrix has been reviewed. Both dc and ac electrical properties of different nanocomposites synthesized have been described. The theoretical models used to explain the experimental results are discussed. It appears that there is a need to have newer theoretical models developed to understand the ac electrical properties of metal-ceramic nanocomposites.
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TL;DR: In this paper, the self-organization of CdSe nanocrystallites into three-dimensional semiconductor quantum dot superiattices (colloidal crystals) is demonstrated.
Abstract: The self-organization of CdSe nanocrystallites into three-dimensional semiconductor quantum dot superiattices (colloidal crystals) is demonstrated. The size and spacing of the dots within the superlattice are controlled with near atomic precision. This control is a result of synthetic advances that provide CdSe nanocrystallites that are monodisperse within the limit of atomic roughness. The methodology is not limited to semiconductor quantum dots but provides general procedures for the preparation and characterization of ordered structures of nanocrystallites from a variety of materials.
36 citations
TL;DR: This paper reviews and enhances numerical models for determining thermal, elastic and electrical properties of carbon nanotube-reinforced polymer composites and validated by comparison with various experimental datasets reported in the recent literature.
Abstract: This paper reviews and enhances numerical models for determining thermal, elastic and electrical properties of carbon nanotube-reinforced polymer composites. For the determination of the effective ...
26 citations
TL;DR: In this paper, the presence of nickel particles of size ∼20nm in the nano-pores of an alumina-silica nanocomposite has been detected using X-ray diffraction and transmission electron micrograph.
14 citations
TL;DR: In this paper, the average particle size of molybdenum carbide is in the range of 5-15 nm and the detailed XRD analyses coupled with thermodynamic arguments show that reduction of ammonium moly bdate is predominantly by in situ generated hydrogen.
Abstract: Molybdenum carbide has been formed in the silica gel matrix by the in situ reduction of ammonium molybdate. The average particle size of molybdenum carbide is in the range of 5-15 nm. The detailed XRD analyses coupled with thermodynamic arguments show that reduction of ammonium molybdate is predominantly by in situ generated hydrogen.
2 citations
TL;DR: The low frequency (20 Hz to 1 MHz) ac conductivity and magnetoconductivity behavior of ceramic nanocomposite (Ni-SiO2) at low temperature down to 77 K are reported in this article.
Abstract: The low frequency (20 Hz to 1 MHz) ac conductivity and magnetoconductivity behaviour of ceramic nanocomposite (Ni-SiO2) at low temperature down to 77 K are reported. The frequency dependent conductivity followed the power law, σ(ω) ∝ ω
s
. The fractional exponent s is a function of temperature and was found to increase with increasing temperature. This type of variation may be attributed to small polaron hopping. A peak present in the loss tangent indicates the presence of a Debye relaxation process. The magnetoconductivity of the samples is positive, which strongly depends on frequency. A firm theoretical explanation of frequency dependent magnetoconductivity is still lacking.
1 citations
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TL;DR: In this paper, photoionization mass spectra obtained for potassium, mixed potassium/sodium and potassium/lithium were used to investigate the properties of the transition metals in terms of their relative thermodynamic stability.
Abstract: Potasium (K x x<40) and sodium(Na x , x<66) clusters were generated in molecular beams and probed by photoionizationmass spectroscopy. Results obtained include measurements of neutral cluster abundances and determinations of ionization potentials. The I. P. values can be rationalized in terms of a global electrostatic model which extrapolates to the bulk work function. This model also applies to transition metals as can be shown by comparng it to the limited experimental data sets available. The I. P.’s of small clusters exhibit ‘‘quantum size’’ effects which can be understood by individual quantum chemical calculations. As previously found for sodium clusters, photoionization mass spectra obtained for potassium, mixed potassium/sodium and potassium/lithium exhibit abundance maxima at M+ 8 and M+ 20, where M is an alkali metal. This has been interpreted in terms of increased thermodynamic stability of the corresponding neutrals relative to neighboring clusters. We present data which show that a spherical jellium model, while providing a set of numbers correlating well with those of preferred stability in alkali clusters, is less successful in explaining other properties.
154 citations
TL;DR: Clear Coulomb blockade effects have been observed in lateral metal nanostructures fabricated by combined electron beam lithography and ionized beam deposition as discussed by the authors, where islands between 2 and 3 nm in diameter were formed in a 25 nm gap for which the effective tunneling capacitance was calculated to be 0.2 aF.
Abstract: Clear Coulomb blockade effects have been observed in lateral metal nanostructures fabricated by combined electron beam lithography and ionized beam deposition. Islands between 2 and 3 nm in diameter were formed in a 25 nm gap for which the effective tunneling capacitance is calculated to be 0.2 aF. Clear Coulomb gaps and staircases were observed at 77 K in current–voltage characteristics. The staircases can still be seen at room temperature but the gaps tend to a nonlinearity in I–V characteristics around zero bias voltage. The total device area is about 0.01 μm2.
153 citations
153 citations
TL;DR: This is the first observation of the so-called Coulomb staircase, expected for the charging of particles with extremely small capacitance by a discrete number of electrons in ultralow-capacitance silver particles sandwiched between artificial tunnel barriers.
Abstract: We have studied electron tunneling in ultralow-capacitance silver particles sandwiched between artificial tunnel barriers. We have observed steps in the current-voltage characteristics of these systems with voltage widths of e/C (C being the capacitance of the particles), and associated current rises of e/RC. This represents the first observationof the so-called Coulomb staircase, expected for the charging of particles with extremely small capacitance by a discrete number of electrons.
150 citations
TL;DR: In this paper, a scaling argument is used to demonstrate the existence of a minimum metallic conductivity with a universal value for two-dimensional random lattices, and the results of a detailed numerical experiment are presented.
Abstract: A scaling argument is used to demonstrate the existence of a minimum metallic conductivity with a universal value for two-dimensional random lattices. We present a summary of the results of a detailed numerical experiment which supports this suggestion and indicates that the minimum metallic conductivity is $(0.12\ifmmode\pm\else\textpm\fi{}0.03)\frac{{e}^{2}}{\ensuremath{\hbar}}$, in fair agreement with some experimental results for inversion layers.
146 citations