ANODIC OXIDE FILMS ON NIOBIUM: THICKNESS, DIELECTRIC CONSTANT, DISPERSION, REFLECTION MINIMA, FORMATION FIELD STRENGTH, AND SURFACE AREA

1960 ◽  
Vol 38 (7) ◽  
pp. 1141-1147 ◽  
Author(s):  
L. Young
Keyword(s):  
Dielectric Constant ◽  
Refractive Index ◽  
Field Strength ◽  
Surface Area ◽  
Current Density ◽  
Ionic Current ◽  
Anodic Oxide ◽  
Dielectric Constants ◽  
A Value ◽  
Spectrophotometric Data

The wavelengths of minimum specular reflectivity (at 11° incidence) due to interference were determined using a spectrophotometer for a series of films formed on chemically polished niobium. With a value of the refractive index n = 2.46 ± 1% at 4358 Å wavelength by the Abelès method (reported elsewhere), the spectrophotometric data give the refractive index as a function of the wavelength λ, n = 2.26 + 0.398/(λ/103 Å − 2.56)1.2. To analyze the spectrophotometric results, an auxiliary measure of thickness was required (though, with the chart given below, the thickness of a film may be determined directly from spectrophotometric measurements alone). A combination of measurements of the a-c. capacity and of the charge required to form the films gives a suitable measure of thickness (in terms of ρ/ε, where ε = dielectric constant and ρ = density) which is not dependent on a knowledge of the true surface area. The spectrophotometric data provide a calibration of this measure of thickness and thus give ε/ρ. With ρ = 4.36 g cm−3 (reported for the bulk amorphous oxide) this gives ε about 41 (compared with about 27.6 for Ta2O5). The effective surface area of the chemically polished metal was then found to be about 7% greater than the apparent area. At the ionic current density used to form the films (10 ma cm−2), the field strength in the oxide was estimated as 4.96 × 106 v cm−1 within a few per cent uncertainty. Because the field to produce a given ionic current is lower than with Ta2O5 films, the capacity of films formed to a given voltage at a given current density and temperature is not so much greater for niobium than for tantalum as the dielectric constants might lead one to expect. It is suggested that there may be a correlation between dielectric constant and ionic conductivity. The Nb2O5 films recrystallize like Ta2O5 films under an applied field but more readily, at least with the purity of metal now available.

HIGH RESISTANCE ANODIC OXIDE FILMS ON ALUMINIUM

1966 ◽  
Vol 44 (20) ◽  
pp. 2409-2413 ◽  
Author(s):  
A. C. Harkness ◽  
L. Young
Keyword(s):  
Thin Film ◽  
Experimental Data ◽  
Dielectric Constant ◽  
Refractive Index ◽  
Steady State ◽  
Oxide Films ◽  
Ionic Current ◽  
Anodic Oxide ◽  
Immersion Method ◽  
State Ionic

The thicknesses of oxide films formed in aqueous borate solutions were obtained by the spectrophotometric method after developing the interference colors by evaporating a very thin film of gold or bismuth onto the oxide. The refractive index of the stripped films was determined by the Becke immersion method as 1.57 to 1.58 at 5 900 Å wavelength. The dielectric constant was estimated as 9.8 ± 0.5. Experimental data on the steady state ionic current density, I, through the oxide as a function of the field strength, E, in the oxide could be represented by I = I0 exp −(W − qaE)/kT where I0 = 2.24 × 107 A cm−2, W = 1.3 ± 0.15 eV, q = 3e, a = 2.95 ± 0.15 Å.

The determination of the thickness, dielectric constant, and other properties of anodic oxide films on tantalum from the interference colours

1958 ◽  
Vol 244 (1236) ◽  
pp. 41-53 ◽  
Keyword(s):  
Dielectric Constant ◽  
Refractive Index ◽  
Oxide Films ◽  
Anodic Oxide ◽  
Effective Dielectric Constant ◽  
Immersion Method ◽  
Anodic Oxide Films ◽  
A Value ◽  
Specular Reflectivity

The thickness of anodic oxide films on chemically polished tantalum was determined from the wavelengths of the minima in the specular reflectivity using a value of the refractive index of 2·20±0·02 at 5900 Ǻ which was measured on detached flakes of the oxide by the immersion method. An auxiliary measure of increments of thickness was required for the analysis of the spectrophotometric measurements. This was provided by the quantity ( Q ∆( 1/ C )) ½ , where Q was the charge which was required to form the increment of thickness, and ∆(1/ C ) was the corresponding increase in the reciprocal capacity. This measure of thickness, like that provided by the colours, is independent of the area. The analysis gives the refractive index between 2800 and 6000 Ǻ, the net phase change in the two reflexions (with certain assumptions), and a value of ϵ/ρ, where ϵ is the effective dielectric constant under the conditions used, and ρ is the density, ρ was determined by weighing specimens in air and water. The value obtained was 7·93 ± 3%, which gives ϵ = 27·6±5%, at 1 kc/s. The effective surface area was then calculated, and was found to be very little different from the apparent area. The field strength during the formation of oxide at 9·55 mA/cm 2 and 25·8° C was found to be 6·61 x 10 6 V/cm and to be constant within experimental error, independent of thickness.

scholarly journals On the measurement of the dielectric constants of liquids, with a determination of the dielectric constant of benzene

1929 ◽  
Vol 123 (792) ◽  
pp. 664-685 ◽  
Keyword(s):  
Dielectric Constant ◽  
Physical Properties ◽  
Dielectric Constants ◽  
Experimental Conditions ◽  
The Past ◽  
A Value ◽  
The Subject ◽  
Important Indication

It has long been recognised that the dielectric constant of a substance gives an important indication of its constitution, and the classical papers of Nernst and Drude giving methods for the determination of dielectric constants, have been followed by a long series of papers giving the dielectric constants of several hundreds of pure liquids and solutions. Since the publication of Debye’s dipole theory in 1912, the literature of the subject has become even more voluminous than before. In surveying the mass of data one is struck by the very large discrepancies which exist in the values obtained by different observers for any one substance, and it is very difficult to decide whether they are due to the difficulty of pre­paring and purifying the substance, differences in experimental conditions such as frequency of the applied E. M. F., or errors in the methods of measure­ment. In order to make it possible to compare the results of different observers, and to provide a fundamental basis for new measurements, it is important that the value of at least one standard liquid should be known with unquestion­able accuracy. The object of the present investigation was to provide such a value. Benzene was chosen as the standard liquid since it has been very widely used in the past, and it is used as a standard in the measurement of other physical properties.

Stiff Polyimides: Chain Orientation And Anisotropy Of The Optical And Dielectric Properties Of Thin Films

1991 ◽  
Vol 227 ◽  
Author(s):  
D. Boese ◽  
S. Herminghaus ◽  
D. Y. Yoon ◽  
J. D. Swalen ◽  
J. F. Rabolt
Keyword(s):  
Thin Films ◽  
Dielectric Constant ◽  
Refractive Index ◽  
Dielectric Properties ◽  
Dielectric Constants ◽  
Polyimide Films ◽  
Lorenz Equation ◽  
Out Of Plane ◽  
Large Anisotropy ◽  
Uv Visible

ABSTRACTThin films of poly(p-phenylene biphenyltetracarboximide), prepared by thermal imidization of the precursor poly(amic acid) on substrates, have been investigated by optical waveguide, UV-visible, infrared (IR), and dielectric spectroscopies. The polyimide films exhibit an extraordinarily large anisotropy in the refractive indices with the in-plane index n║ = 1.852 and the out-of-plane index n┴ = 1.612 at 632.8 nm wavelength, indicating a strong preference of polymer chains to orient along the film plane. No discernible effect of the film thickness on this optical anisotropy is found in the range of ca. 0.4 μm to 7.8 μm in thickness. The frequency dispersion of the in-plane refractive index to 1.06 μm wavelength is consistent with the results calculated by the Lorentz-Lorenz equation from the UV-visible spectrum. The contribution from the entire IR range from 7000 to 200 cm,−1 computed by the Spitzer-Kleinmann dispersion relations from the measured spectra, adds ca. 0.07 to the in-plane refractive index n║. Approximately the same increase is assumed for the out-of-plane index n┴, based on the tilt-angle dependent IR results. Application of the Maxwell relation leads to the out-of-plane dielectric constant ε┴≃2.8 at ca. 1013 Hz, as compared with the measured value of ca. 3.0 at 106 Hz. Assuming this small difference to remain the same for the in-plane dielectric constants ε║, we obtain a a very large anisotropy in the dielectric properties of these polyimide films with the estimated in-plane dielectric constant ε║≃3.5 at ca. 1013 Hz, and ε.≃3.7 at 106 Hz.

scholarly journals Dielectric Constant, Metallization Criterion and Optical Properties of CuO Doped TeO2-B2O3 Glasses

2021 ◽  
Author(s):  
NAZIRUL NAZRIN SHAHROL NIDZAM ◽  
S.A. Umar ◽  
M.K. Halimah ◽  
M.M. Marian ◽  
Z.W. Najwa ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Refractive Index ◽  
Molar Volume ◽  
Copper Ion ◽  
Volume Density ◽  
Dielectric Constants ◽  
Physical Parameters ◽  
Laser Applications ◽  
Optical Dielectric Constant ◽  
Ftir Spectral Analysis

Abstract Copper oxide doped TeO2 – B2O3 glass system with empirical formula; [(B2O3)0.3(TeO2)0.7]1-x(CuO)x using the melt quenching method, where x = 0.0, 0.01, 0.015, 0.02, and 0.025 was combined. The glass samples’ density and molar volume were measured, followed by characterizations using the UV-Vis, Fourier transform infrared (FTIR) and X-ray diffraction (XRD) spectroscopes. The amorphous or glassy nature of glass samples was proven by the XRD spectra except for the pure borotellurite sample which showed a peak around 2θ = 20o, indicating α-TeO2 crystalline phase presence. The FTIR spectral analysis suggested the presence of BO3, TeO3 and TeO4 as the structural functional units in the glass samples. The UV-Vis spectra showed no presence of any sharply defined edges, affirming the amorphous or glassy nature of the glass materials. Physical parameters e.g. molar volume, density, oxygen packing density (OPD), inter ionic distance of Cu2+ ions, concentration of copper ion per unit volume (N), as well as the polaron radius data were presented and discussed. Also, the direct bandgap (3.8900 to 3.5900 eV) , indirect bandgap (3.3200 to 3.0800 eV), refractive index (2.318 to 2.378), dielectric constant (5.3731 to 5.6549), optical dielectric constant (4.3731 to 4.6549), refractive index based metallization criterion (0.406885 to 0.391916) and the band gap based metallization criterion (0.407431 to 0.392428) were analysed and discussed. Based on the metallization criterion and values of refractive index, the glasses are good candidates for optoelectronic and laser applications. Meanwhile, the dielectric constants’ values of the present glasses indicate their suitability bandpass filters and microelectronic substrates applications.

Microwave properties of saturated reservoirs

Geophysics ◽  
1983 ◽  
Vol 48 (3) ◽  
pp. 367-375 ◽  
Author(s):  
James N. Lange
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Surface Area ◽  
Oil And Gas ◽  
Volume Fraction ◽  
Empirical Relationship ◽  
Dielectric Constants ◽  
Solid Matrix ◽  
Detailed Model

Dielectric properties of saturated, porous geologic materials reflect the large difference in dielectric constant ε of typical saturating fluids such as water (ε = 78) or oil and gas (ε = 1–3). The deconvolution of in‐situ dielectric properties of saturated porous materials into the component parts requires a detailed model of the composite material. Defining aspects of this model in the microwave frequency regime is the primary purpose of this investigation. A model is examined in which the dielectric constant of the composite is equal to the sum of the dielectric constants of the components weighted by the volume fraction occupied by each. That model is compared to measurements at microwave frequencies made on systems consisting of glass beads, quartz, or sand saturated with chlorobenzene, 1,2‐dichloroethane, methanol, or air, and find satisfactory agreement. When water is the saturant an interaction between water and the solid matrix has an important effect on the composite dielectric constant. This interaction is observed to be particularly large for quartz and water and suppresses the composite dielectric constant quite considerably. This interaction is dependent upon the relative surface area per unit volume. An empirical relationship between the surface area and composite dielectric constant is obtained for clean, saturated, unconsolidated reservoirs. The inverse process of determining surface area from in‐situ measurements of the composite dielectric constant may be possible for clean reservoirs of known lithology. In sandstones from cores the dielectric constant is also below the volume fraction model and corrections are needed to evaluate water content.

Enhancement of the Electrical Properties of BaTiO3 Films on GaAs Using Double Layer Structures

1994 ◽  
Vol 361 ◽  
Author(s):  
L.H. Chang ◽  
W.A. Anderson
Keyword(s):  
Thin Films ◽  
Dielectric Constant ◽  
Electrical Properties ◽  
Charge Density ◽  
Leakage Current ◽  
Leakage Current Density ◽  
Double Layer ◽  
Current Density ◽  
Dielectric Constants ◽  
Oxide Charge

ABSTRACTFerroelectric BaTiO3 thin films have been directly deposited on n-GaAs with carrier concentration of 5.3–8.2×1017/cm2. The BaTiO3 thin films with a thickness in the range of 80–120 nm were prepared by RF magnetron sputtering with a substrate temperature of 300°C. The as-deposited BaTiO3 films appeared to be amorphous with relative dielectric constants of around 15 and gave flat capacitance-voltage (C-V) curves, indicating poor interface properties and very high oxide charge density. After rapid thermal annealing (RTA) at 800°C for 60 sec, the relative dielectric constant of the BaTiO3 film increased to 82 and a sharp C-V curve was observed with oxide charge density of about 7×1012/cm2. However, the leakage current density increased from 4×10'11 A/cm2 for as-deposited BaTiO3 to 2×105 A/cm2 for RTA(800°C)-BaTiO3 at a field of 4×105 V/cm. By taking advantage of the best properties from both as-deposited amorphous BaTiO3 films (low leakage current density) and RTA(800°C)-BaTiO3 (high dielectric constant) the double layer structure was designed to enhance the electrical properties of the BaTiO3 films on GaAs. The most promising results in regards to the dielectric property and leakage current density are 76.5 and 9.7×109 A/cm2, respectively, for the double layer RTA(500°C)-BaTiO3 on RTA(800°C)-BaTiO3 structures.

MEASUREMENT OF THE DIELECTRIC CONSTANT OF CELLULOSE

1938 ◽  
Vol 16b (8) ◽  
pp. 273-288 ◽  
Author(s):  
H. A. De Luca ◽  
W. Boyd Campbell ◽  
O. Maass
Keyword(s):  
Dielectric Constant ◽  
Fibrous Material ◽  
Dielectric Constants ◽  
Ethylene Dichloride ◽  
Percentage Composition ◽  
A Value ◽  
Miscible Liquids ◽  
Point Of Intersection

A method has been devised for the measurement of the dielectric constant of a material that cannot be made to completely fill a condenser. The following is the procedure adopted: Two completely miscible liquids are so chosen that the dielectric constant of the material under examination lies between the two values for the liquids. The dielectric constants of solutions of A and B ranging from 100% A to 100% B are measured. A curve is drawn showing the relation between dielectric constant and percentage composition. The condenser used is then partly filled with the fibrous material. The solutions of A and B are introduced into the condenser and the net dielectric constants are determined. A second curve is drawn showing this relation. The point of intersection of the two curves gives the composition of that liquid that has the same dielectric constant as the fibrous material.This method has been applied to the measurement of the dielectric constant of cellulose, benzene and ethylene dichloride being used. A value of 6.1 has been obtained for this constant.

scholarly journals Growth Kinetics of Anodic Oxide Films Formed on Zircaloy-2 in Various Electrolytes

2009 ◽  
Vol 6 (3) ◽  
pp. 880-886
Author(s):  
V. Jeevana Jyothi ◽  
CH. Anjaneyulu
Keyword(s):  
Current Density ◽  
Formation Rate ◽  
Ionic Current ◽  
Anodic Oxide ◽  
Anodic Films ◽  
Differential Field ◽  
Increase With Increase ◽  
Jump Distance ◽  
Current Densities ◽  
Kinetics Of

The Kinetics of anodic oxidation of zircaloy-2 have been studied at current densities ranging from 4 to 12 mA cm-2at room temperature in order to investigate the dependence of ionic current density on the field across the oxide film. Thickness of the anodic films was estimated from capacitance data. The formation rate, current efficiency and differential field were found to increase with increase in the ionic current density for zircaloy-2. Plots of logarithm of formation ratevs. logarithm of current density is fairly linear. From linear plots of logarithm of ionic current densityvs. differential field and applying the Cabrera - Mott theory, the half - jump distance (a) and height of energy barrier (W) were deduced.

High field kinetic processes in anodic oxide films on aluminium. II. Current transients for constant field conditions

1968 ◽  
Vol 46 (4) ◽  
pp. 549-556 ◽  
Author(s):  
M. J. Dignam ◽  
P. J. Ryan
Keyword(s):  
Field Strength ◽  
Oxide Films ◽  
Ionic Current ◽  
Anodic Oxide ◽  
Field Conditions ◽  
Electrolysis Cell ◽  
Constant Field ◽  
Zero Field ◽  
Anodic Oxide Films ◽  
Current Transients

Anodic oxide films were formed on high purity aluminium (99.996%) in a glycol–borate electrolyte. Following aging of the films under zero field conditions either at room temperature or 60 °C the electrodes were returned to the electrolysis cell where the anodic overpotential was increased rapidly until a predetermined value was reached, then maintained constant. The ensuing current transients were recorded and analyzed. As little film growth occurred during these measurements the conditions correspond closely to constant field strength. For sufficiently low field strengths the observed current decreased monotonically with increasing time. No single empirical equation could be found to represent these data, although they appear to be in the nature of charging currents rather than ion currents. For somewhat higher applied fields the current is observed to decrease initially, reach a minimum, and then increase approaching ultimately the steady-state ion current for the applied field strength. These data can be accounted for satisfactorily by only the polarization theory of ionic current transients.

Sign in / Sign up

Export Citation Format

Share Document