Drop of the dielectric constant of some aliphatic primary alcohols in thin layers between two vitreous carbon plates

2003 ◽  
Vol 661-662 ◽  
pp. 587-593
Author(s):  
Uwe Franken ◽  
Gerhard Peschel
Keyword(s):  
Dielectric Constant ◽  
Thin Layers ◽  
Vitreous Carbon ◽  
Primary Alcohols

Radio-wave reflectivity from cold glaciers

2020 ◽  
Author(s):  
Olga Yushkova ◽  
Taisiya Dymova ◽  
Viktor Popovnin
Keyword(s):  
Dielectric Constant ◽  
Dielectric Permittivity ◽  
Reflection Coefficient ◽  
Surface Temperature ◽  
Frequency Dependence ◽  
Depth Profile ◽  
Loss Tangent ◽  
Thin Layers ◽  
The Arctic ◽  
Radio Waves

<p>Radio echo-sounding is a powerful technique for investigating the subsurface of the glaciers. However, physics underlying the formation of the reflected signal is sometimes oversimplified  in the geophysical glacier studies, leading to wrong results. Various remote sensing techniques use different wavelengths (e.g., 13.575 GHz for CryoSat and 20-25/200-600 MHz for ground-penetrating radar), but it is still not clear which particular wavelengths are the best to detect different characteristics of the ice. Possibly, the results gained using different wavelengths may not coincide but rather complement each other due to frequency dependence of the dielectric permittivity and conductivity of snow, ice and especially water.</p><p>Here we attempt to construct an electrophysical model of a cold glacier. This mathematical model considers the variability of the depth profile of the complex dielectric permittivity depending on the frequency of the probing radio signal and the surface temperature. A series of calculations of the reflection coefficients of radio waves from the modelled glacier show that at low temperatures for frequencies above 1 MHz the real part of the dielectric constant of the glacier does not change with frequency and surface temperature, but depends on the glacier structure, while the depth profile of the loss tangent is constant throughout the glacier.  As wavelength decreases, the absorption of radio-waves by the glacier decreases and the frequency dependence of the reflection coefficient becomes a periodic function, its period and amplitude depend on the glacier thickness, the dielectric constant of the bedrock and ice on the surface.</p><p>The range of radio-waves from 0.1 to 1 MHz is not optimal for sounding cold glaciers: the absorption of radio-waves by ice is large for studying thick layers of the glacier, and the wavelength does not allow studying thin layers. Hence, reflection from the glacier surface prevails upon reflection of the signal. The small absorption of short radio waves by ice leads to the fact that the frequency dependence of the reflection coefficient of short radio-waves is practically the sum of the partial reflections of radio-waves from the surface and internal snow/firn and firn/ice boundaries. Period and amplitude of oscillations of the function  depend on the depth of the internal boundaries and the gradient of dielectric characteristics of ice, snow, firn and bedrock.</p><p>Changes in surface temperature, leading to a change in the loss tangent of the upper glacier layers, are manifested in the phase magnitude of the reflection coefficient of radio-waves:it grows with the temperature. Theoretically, the high-frequency signal reflected from the glacier contains information about the structure of the cold glacier and the depth distribution of the dielectric constant, but to restore the electrophysical parameters of the glaciers, it is necessary to use a broadband signal with smooth spectrum and high digitization speed.</p><p>The reported study was funded by RFBR, project number 18-05-60080 (“Dangerous nival-glacial and cryogenic processes and their impact on infrastructure in the Arctic”).</p>

Low Temperature Dielectric Properties of BST/ZrO2 Multilayer Films

2003 ◽  
Vol 784 ◽  
Author(s):  
Santosh K. Sahoo ◽  
D. C. Agrawal ◽  
S. B. Majumder ◽  
R. S. Katiyar ◽  
Y. N. Mohapatra
Keyword(s):  
Thin Films ◽  
Dielectric Constant ◽  
Low Temperature ◽  
Leakage Current ◽  
Complex Function ◽  
Multilayer Films ◽  
Thin Layers ◽  
Total Thickness ◽  
Constant Multiple ◽  
Number Of Layers

ABSTRACTThin films of Ba1-x SrxTiO3 (BST) are being actively investigated for applications in dynamic random access memories (DRAM) because of their properties such as high dielectric constant, low leakage current, and low fatigue. Several approaches have been used to improve the properties of thin films such as doping with aliovalent dopants, graded compositions, and layered structures. We have found that interposing layers of an electronic insulator such as ZrO2 in between BST layers results in a significant reduction in the leakage current. In this paper the low temperature electrical properties of these multilayer structures are reported. The structures consist of alternate layers of Ba0.8Sr0.2TiO3 and ZrO2 deposited by a sol-gel process on platinized Si substrates. The thickness and the number of layers are varied while keeping the total thickness of the film constant. Multiple peaks in the dielectric constant vs temperature plots at all frequencies are observed in the multilayered films. The properties of the multilayer films are a complex function of the number of layers and their thicknesses. A structure with several thin layers of ZrO2 interposed between the BST layers produces smoother plots than a single layer of ZrO2 of same total thickness. This is attributed to more uniform distribution, as determined by XPS, of ZrO2 in the multilayer structure due to smaller diffusion distances.

DETECTION OF THIN LAYERS BY RADIO INTERFEROMETRY

Geophysics ◽  
1975 ◽  
Vol 40 (2) ◽  
pp. 299-308 ◽  
Author(s):  
J. R. Rossiter ◽  
D. W. Strangway ◽  
A. P. Annan ◽  
R. D. Watts ◽  
J. D. Redman
Keyword(s):  
Dielectric Constant ◽  
Half Space ◽  
Free Space ◽  
Single Mode ◽  
Theoretical Work ◽  
Field Work ◽  
Thin Layers ◽  
Radio Interferometry ◽  
Snow Layer ◽  
Recent Theoretical Work

Recent theoretical work on the radio interferometry technique for dielectric layers less than one free space wavelength thick has indicated that there is a thickness for which no interference is observed. This thickness is about 0.2 free space wavelengths for ice, and it lies between the thickness that allows one single mode to propagate in the layer (>0.2 wavelengths) and a thickness that is essentially transparent to the wavelength being used (⩽0.2 wavelengths). Field work was done on the Juneau Icefield, Alaska; frequencies from 1 to 32 Mhz were used. At 1 and 2 Mhz, an interference pattern typical of a half‐space of ice with a dielectric constant of 3.3 was observed, while at 4 Mhz essentially no interference was seen. At higher frequencies, the interference observed is typical of that of a layer overlying a half‐space. The upper layer can be interpreted to have a thickness of 15 or 20 m (0.2 wavelengths at 4 Mhz) with a dielectric constant of 2.4. These results are for a layer of snow over a half‐space of ice. The technique is therefore of potential interest in interpreting the nature of the snow layer overlying a glacier.

scholarly journals Dielectric Relaxation Studies of Ethyl Formate with Primary Alcohols using Time Domain Reflectometry

2012 ◽  
Vol 9 (1) ◽  
pp. 81-83 ◽  
Author(s):  
S. Elangovan ◽  
S. Mullainathan
Keyword(s):  
Dielectric Constant ◽  
Relaxation Time ◽  
Dielectric Relaxation ◽  
Chain Length ◽  
Ethyl Formate ◽  
Time Domain Reflectometry ◽  
Carbon Chain Length ◽  
Primary Alcohols ◽  
Dielectric Parameters ◽  
Relaxation Studies

Dielectric relaxation studies of ethylformate with 1-propanol,1-butanol and 1-pentanol binary mixtures have been carried out at micro frequency range 9.36 GHZ at temperature of 303K.Different dielectric parameters like dielectric constant(ε’ ),dielectric loss (ε’’) ,Static dielectric constant (ε0) and dielectric constant at optical frequency (ε∞) have been determined. The Relaxation time (ε) has been obtained by Higasi and Cole-Cole method. The dielectric constant (τ0) and relaxation time (τ) decreased with increasing the concentration of ethylformate in alcohol system. The relaxation time (τ) increased with increase in chain length of the alcohols. The result shows that the strength of this molecular interaction depends upon the carbon chain length of the alcohols. Hence the proton donating ability of alcohols is in the order of 1-propanol<1-butanol<1-pentanol

Immunoferritin localization of intracellular antigens in positively stained frozen sections

1978 ◽  
Vol 36 (2) ◽  
pp. 168-169
Author(s):  
K. T. Tokuyasu
Keyword(s):  
Surface Tension ◽  
Water Surface ◽  
Thin Layers ◽  
The Other ◽  
Positive Staining ◽  
Frozen Sections ◽  
The Past ◽  
Ultrathin Frozen Sections ◽  
Definition Of

During the past investigations of immunoferritin localization of intracellular antigens in ultrathin frozen sections, we found that the degree of negative staining required to delineate u1trastructural details was often too dense for the recognition of ferritin particles. The quality of positive staining of ultrathin frozen sections, on the other hand, has generally been far inferior to that attainable in conventional plastic embedded sections, particularly in the definition of membranes. As we discussed before, a main cause of this difficulty seemed to be the vulnerability of frozen sections to the damaging effects of air-water surface tension at the time of drying of the sections.Indeed, we found that the quality of positive staining is greatly improved when positively stained frozen sections are protected against the effects of surface tension by embedding them in thin layers of mechanically stable materials at the time of drying (unpublished).

EELS Measurement of the Local Electronic Structure of Copper Atoms Segregated to Aluminum Grain Boundaries

1996 ◽  
Vol 54 ◽  
pp. 342-343
Author(s):  
S.J. Splinter ◽  
J. Bruley ◽  
P.E. Batson ◽  
D.A. Smith ◽  
R. Rosenberg
Keyword(s):  
Electronic Structure ◽  
Grain Boundaries ◽  
Boundary Segregation ◽  
Thin Layers ◽  
Nominal Composition ◽  
Spatially Resolved ◽  
Service Lifetime ◽  
Heat Treated ◽  
Probe Size ◽  
Local Electronic Structure

It has long been known that the addition of Cu to Al interconnects improves the resistance to electromigration failure. It is generally accepted that this improvement is the result of Cu segregation to Al grain boundaries. The exact mechanism by which segregated Cu increases service lifetime is not understood, although it has been suggested that the formation of thin layers of θ-CuA12 (or some metastable substoichiometric precursor, θ’ or θ”) at the boundaries may be necessary. This paper reports measurements of the local electronic structure of Cu atoms segregated to Al grain boundaries using spatially resolved EELS in a UHV STEM. It is shown that segregated Cu exists in a chemical environment similar to that of Cu atoms in bulk θ-phase precipitates.Films of 100 nm thickness and nominal composition Al-2.5wt%Cu were deposited by sputtering from alloy targets onto NaCl substrates. The samples were solution heat treated at 748K for 30 min and aged at 523K for 4 h to promote equilibrium grain boundary segregation. EELS measurements were made using a Gatan 666 PEELS spectrometer interfaced to a VG HB501 STEM operating at 100 keV. The probe size was estimated to be 1 nm FWHM. Grain boundaries with the narrowest projected width were chosen for analysis. EDX measurements of Cu segregation were made using a VG HB603 STEM.

Microstructural characterization of YBaCuO Films on LaAlO3 substrates

1989 ◽  
Vol 47 ◽  
pp. 180-181
Author(s):  
E. L. Hall ◽  
A. Mogro-Campero ◽  
N. Lewis ◽  
L. G. Turner
Keyword(s):  
Dielectric Constant ◽  
Single Crystal ◽  
Film Growth ◽  
Microstructural Characterization ◽  
Lattice Parameter ◽  
Film Plane ◽  
Substrate Material ◽  
High Loss ◽  
Amorphous Substrates ◽  
High Dielectric

There have been a large number of recent studies of the growth of Y-Ba-Cu-O thin films, and these studies have employed a variety of substrates and growth techniques. To date, the highest values of Tc and Jc have been found for films grown by sputtering or coevaporation on single-crystal SrTiO3 substrates, which produces a uniaxially-aligned film with the YBa2Cu3Ox c-axis normal to the film plane. Multilayer growth of films on the same substrate produces a triaxially-aligned film (regions of the film have their c-axis parallel to each of the three substrate <100> directions) with lower values of Jc. Growth of films on a variety of other polycrystalline or amorphous substrates produces randomly-oriented polycrystalline films with low Jc. Although single-crystal SrTiO3 thus produces the best results, this substrate material has a number of undesireable characteristics relative to electronic applications, including very high dielectric constant and a high loss tangent at microwave frequencies. Recently, Simon et al. have shown that LaAlO3 could be used as a substrate for YBaCuO film growth. This substrate is essentially a cubic perovskite with a lattice parameter of 0.3792nm (it has a slight rhombohedral distortion at room temperature) and this material exhibits much lower dielectric constant and microwave loss tangents than SrTiO3. It is also interesting from a film growth standpoint since it has a slightly smaller lattice parameter than YBa2Cu3Ox (a=0.382nm, b=c/3=0.389nm), while SrTiO3 is slightly larger (a=0.3905nm).

Enhanced performance of supercapacitors by constructing a “mini parallel-plate capacitor” in an electrode with high dielectric constant materials

2020 ◽  
Vol 8 (32) ◽  
pp. 16661-16668
Author(s):  
Huayao Tu ◽  
Shouzhi Wang ◽  
Hehe Jiang ◽  
Zhenyan Liang ◽  
Dong Shi ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Carbon Fiber ◽  
Parallel Plate ◽  
Sandwich Structure ◽  
High Dielectric Constant ◽  
Parallel Plate Capacitor ◽  
Plate Capacitor ◽  
Fiber Metal ◽  
High Dielectric ◽  
Mini Plate

The carbon fiber/metal oxide/metal oxynitride layer sandwich structure is constructed in the electrode to form a mini-plate capacitor. High dielectric constant metal oxides act as dielectric to increase their capacitance.

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