scholarly journals AC conductivity and correlation effects in nano-granular Pt/C

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Marc Hanefeld ◽  
Peter Gruszka ◽  
Michael Huth
Keyword(s):  
Ac Conductivity ◽  
Finite Size ◽  
Dielectric Materials ◽  
Electronic Systems ◽  
Correlation Effects ◽  
Temperature Dependent ◽  
Tunnel Coupling ◽  
Transport Regime ◽  
Metallic Grains ◽  
Nano Grains

AbstractNano-granular metals are materials that fall into the general class of granular electronic systems in which the interplay of electronic correlations, disorder and finite size effects can be studied. The charge transport in nano-granular metals is dominated by thermally-assisted, sequential and correlated tunneling over a temperature-dependent number of metallic grains. Here we study the frequency-dependent conductivity (AC conductivity) of nano-granular Platinum with Pt nano-grains embedded into amorphous carbon (C). We focus on the transport regime on the insulating side of the insulator metal transition reflected by a set of samples covering a range of tunnel-coupling strengths. In this transport regime polarization contributions to the AC conductivity are small and correlation effects in the transport of free charges are expected to be particularly pronounced. We find a universal behavior in the frequency dependence that can be traced back to the temperature-dependent zero-frequency conductivity (DC conductivity) of Pt/C within a simple lumped-circuit analysis. Our results are in contradistinction to previous work on nano-granular Pd/$$\hbox {ZrO}_2$$ ZrO 2 in the very weak coupling regime where polarization contributions to the AC conductivity dominated. We describe possible future applications of nano-granular metals in proximity impedance spectroscopy of dielectric materials.

Theory of ultrasonic attenuation in one and two dimensional metals

1976 ◽  
Vol 54 (14) ◽  
pp. 1454-1460 ◽  
Author(s):  
T. Tiedje ◽  
R. R. Haering
Keyword(s):  
Ultrasonic Attenuation ◽  
Three Dimensional ◽  
Electronic Systems ◽  
Two Dimensional ◽  
Temperature Dependent ◽  
One Dimensional ◽  
The Difference

The theory of ultrasonic attenuation in metals is extended so that it applies to quasi one and two dimensional electronic systems. It is shown that the attenuation in such systems differs significantly from the well-known results for three dimensional systems. The difference is particularly marked for one dimensional systems, for which the attenuation is shown to be strongly temperature dependent.

Temperature-dependent AC conductivity and dielectric and impedance properties of ternary In–Te–Se nanocomposite thin films

2019 ◽  
Vol 125 (7) ◽  
Author(s):  
Pandian Mannu ◽  
Matheswaran Palanisamy ◽  
Gokul Bangaru ◽  
Sathyamoorthy Ramakrishnan ◽  
Asokan Kandasami ◽  
...  
Keyword(s):  
Thin Films ◽  
Ac Conductivity ◽  
Temperature Dependent ◽  
Nanocomposite Thin Films

Temperature-Dependent ac Conductivity of the Fibonacci Lattice

1999 ◽  
Vol 16 (7) ◽  
pp. 529-531 ◽  
Author(s):  
Jian-wen Ding ◽  
Xiao-hong Yan ◽  
Xian-cheng Fang
Keyword(s):  
Ac Conductivity ◽  
Temperature Dependent ◽  
Fibonacci Lattice

Dielectric and ac Conductivity Studies on Nanocrystalline Mn Modified Cobalt Ferrite

2018 ◽  
Vol 24 (8) ◽  
pp. 5629-5632 ◽  
Author(s):  
Sweety Supriya ◽  
Sunil Kumar ◽  
Manoranjan Kar
Keyword(s):  
Dielectric Constant ◽  
Frequency Response ◽  
Electrical Transport ◽  
Ac Conductivity ◽  
Cobalt Ferrite ◽  
Electrical Transport Properties ◽  
Arrhenius Behavior ◽  
Temperature Dependent ◽  
Two Layer Model ◽  
Frequency Temperature

The ac conductivity and dielectric properties on CoFe2−xMnxO4 for x = 0.00, 0.10, 0.15 and 0.20 have been studied in detail. All the samples were prepared in nanocrystalline size. These materials are found to be crystallized to Fd <mml:math display="block"> <mml:semantics> <mml:mover accent="true"> <mml:mi>3</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> </mml:semantics> </mml:math> m space group in cubic spinel structure. The dielectric constant and ac conductivity has been discussed as a function of frequency, temperature and composition. The relation between dielectric constant and ac conductivity has been analyzed and the results validate each other. The frequency response of ac conductivity (σac) obeys Johnschers power law and the parameters obtained, explain the sources of ac and dc electrical conductivity in the material. The frequency response of σac follows Maxwell–Wagner two-layer model. The influence of frequency as pumping force on activation energy has been determined. The temperature dependent ac conductivity shows the Arrhenius behavior. The σac observed to be enhanced with increase in frequency as well as temperature. The semiconducting behavior (NTCR) was also evident from temperature dependent electrical transport properties study. The low value of ac conductivity suggests a possible use of this material in dielectric applications.

Impact of Growth Temperature, Pressure, and Strain on the Morphology of GaN Films

1996 ◽  
Vol 449 ◽  
Author(s):  
H. Fujii ◽  
C. Kisielowski ◽  
J. Krueger ◽  
M. S. H. Leung ◽  
R. Klockenbrink ◽  
...  
Keyword(s):  
Finite Size ◽  
Growth Mode ◽  
Temperature Dependent ◽  
Grain Sizes ◽  
Sapphire Substrates ◽  
Size Limitation ◽  
Different Temperatures ◽  
Bulk Gan ◽  
Gas Molecules ◽  
Background Gas

ABSTRACTGaN films grown on sapphire at different temperatures are investigated. A Volmer-Weber growth mode is observed at temperatures below 1000K that leads to thin films composed of oriented grains with finite size. Their size is temperature dependent and can actively be influenced by strain. Largest grains are observed in compressed films. It is argued that diffusing Ga ad-atoms dominate the observed effects with an activation energy of 2.3 ± 0.5 eV. Comparably large grain sizes are observed in films grown on off-axes sapphire substrates and on bulk GaN. This assures that the observed size limitation is a consequence of the 3D growth mode and not dependent on the choice of the substrate. In addition, the grain size and the surface roughness of the films depend on the nitrogen partial pressure in the molecular beam epitaxy (MBE) chamber,most likely due to collisions between the reactive species and the background gas molecules. This effect is utilized to grow improved nucleation layers on sapphire.

Frequency Dependent Charge Transport and Spin State Switching Characteristics of Fe(phen)2(NCS)2 in Polymer

2020 ◽  
Vol 20 (5) ◽  
pp. 2803-2812
Author(s):  
Chaitali Mondal ◽  
M. L. Nanda Goswami ◽  
Swapan K. Mandal
Keyword(s):  
Charge Transport ◽  
Spin State ◽  
Ac Conductivity ◽  
Spin Transition ◽  
Hysteresis Loops ◽  
State Dependence ◽  
Temperature Dependent ◽  
Thermal Dependence ◽  
The Difference ◽  
Composite Samples

We report on the bistability in spin states of spin crossover (SCO) compound Fe(phen)2(NCS)2 in polymer (polypyrrole) by frequency (1–100 kHz) and temperature dependent (305–457 K) electrical conductivity measurements. The structure and growth of SCO compounds in conducting polymer are obtained by scanning electron microscopy, X-ray diffraction and optical absorption measurements. The thermal dependence of ac conductivity σ(ω) shows the clear formation of a hysteresis loop in its cooling and heating cycle due to the difference in conductivity in high spin and low spin state. The size, shape and width of the hysteresis loops are found to be critically dependent on the applied frequency and/or the ratio between SCO and polymer. The ac conductivity is found to exhibit a dispersive behavior following Jonscher’s law: σ(ω) ∝ ωn below a critical frequency ωc, above which it is found to monotonically decrease with increasing frequency. The thermal dependence of the exponent n and ωc is also explored. The charge transport phenomena are explained in the framework of hopping of charge carriers. The data reveals that addition of polymer can play an important role to tune the conductivity of SCO compounds and its spin state dependence characteristics which may be quite helpful for fabricating future spin-based devices. Temperature dependent magnetic susceptibility measurement also confirms the spin transition behavior of the SCO/ppy composite samples. These SCO/ppy composite samples can be taken as the reliable nanomaterials fabricated with the concept of future spin based nanoarchitectonics.

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