Ionic Conduction Mechanisms in CaF2 and CaF2-Al2O3 Nanocomposite Films on Al2O3 Substrates

1993 ◽  
Vol 318 ◽  
Author(s):  
F. A. Modine ◽  
D. Lubben ◽  
J. B. Bates
Keyword(s):  
Activation Energy ◽  
Electrical Conductivity ◽  
Ionic Conduction ◽  
Electrical Conductance ◽  
High Conductivity ◽  
Nanocomposite Films ◽  
Second Phase ◽  
Mole Percent ◽  
Interdigital Electrodes

ABSTRACTThin films of pure CaF2 and nanocomposite mixtures of Al2O3 with CaF2 were sublimated on Al2O3 substrates. Interdigital electrodes allowed in situ measurements of the electrical conduction of films as a function of thickness, deposition rate, composition, time, and temperature. The electrical conductivity in pure CaF2 adjacent to an Al2O3 interface sometimes exceeded the bulk CaF2 conductivity (i.e., value at more than 50 nm distance) by as much as a factor of 6700 at 200°C. The high conductivity is characterized by an activation energy of 0.6 ± 0.1 eV, which is significantly lower than the activation energy of about 1.0 eV for conduction in the bulk. However, this high conductivity is thermally unstable and diminishes in time. A high but stable conductivity was obtained in CaF2 films containing about 10 mole percent Al2O3 as a dispersed second phase. At 200°C, a 2-phase film gave a factor of 360 enhancement over the measured bulk CaF2 conductivity and a factor of 7 improvement over the best previously reported conductivity for CaF2-Al203 composite materials. The origin of enhanced conduction in CaF2 is attributed to ion transport along dislocations. Dislocations anneal with a characteristic log of time dependence that is recognizable in the annealing behavior of the electrical conductivity. Presumably, the addition of a dispersed second phase of Al2O3 to CaF2 serves both to generate and to pin dislocations; the electrical conductance is thereby enhanced and stabilized.

Deposition and Crystallisation Behaviour of Amorphous Silicon Thin Films Obtained by Pyrolysis of Disilane Gas at Very Low Pressure

1994 ◽  
Vol 345 ◽  
Author(s):  
T. Kretz ◽  
D. Pribat ◽  
P. Legagneux ◽  
F. Plais ◽  
O. Huet ◽  
...  
Keyword(s):  
Activation Energy ◽  
Growth Rate ◽  
Amorphous Silicon ◽  
Vapor Deposition ◽  
Electrical Conductance ◽  
Chemical Vapor ◽  
Crystalline Fraction ◽  
Silicon Thin Films ◽  
Crystallisation Behaviour

AbstractHigh purity amorphous silicon layers were obtained by ultrahigh vacuum (millitorr range) chemical vapor deposition (UHVCVD) from disilane gas. The crystalline fraction of the films was monitored by in situ electrical conductance measurements performed during isothermal annealings. The experimental conductance curves were fitted with an analytical expression, from which the characteristic crystallisation time, tc, was extracted. Using the activation energy for the growth rate extracted from our previous work, we were able to determine the activation energy for the nucleation rate for the analysed-films. For the films including small crystallites we have obtained En ∼ 2.8 eV, compared to En ∼ 3.7 eV for the completely amorphous ones.

Dehydration and decomposition of pyrophyllite at high pressures: electrical conductivity and X-ray diffraction studies to 5 GPa

1997 ◽  
Vol 34 (6) ◽  
pp. 875-882 ◽  
Author(s):  
Tara L. Hicks ◽  
Richard A. Secco
Keyword(s):  
Electrical Conductivity ◽  
South African ◽  
Pressure Dependence ◽  
High Pressures ◽  
Ionic Conduction ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Temperature Dependence Of Conductivity

The dehydration and decomposition of South African pyrophyllite were studied in the pressure range 2.5–5.0 GPa and in the temperature (T) range 295–1473 K using both in situ electrical conductivity measurements and X-ray diffraction studies on the recovered samples. Activation energies for conduction (Qc) vary in the range 0.02–0.07 eV for T ≤ 500 K where the dominant conduction mode is electronic, and Qc is in the range 1.10–1.28 eV for T ≥ 500 K where ionic conduction dominates. Abrupt changes in the isobaric temperature dependence of conductivity mark the onset of dehydration and subsequent decomposition into kyanite plus quartz–coesite. At 2.5 GPa, South African pyrophyllite forms the dehydroxylate phase at 760 K with a pressure dependence of ~30 K/GPa and complete decomposition follows at 1080 K with a pressure dependence of ~41 K/GPa. The resulting pressure–temperature phase diagram is in very good agreement with many previous studies at 1 atm (101.325 kPa).

scholarly journals Processible nanomaterials with high conductivity and magnetizability. Preparation and properties of maghemite/polyaniline nanocomposite films

2000 ◽  
Vol 72 (1-2) ◽  
pp. 157-162 ◽  
Author(s):  
Ben Zhong Tang ◽  
Yanhou Geng ◽  
Qunhui Sun ◽  
Xi Xiang Zhang ◽  
Xiabin Jing
Keyword(s):  
Electrical Conductivity ◽  
Magnetic Susceptibility ◽  
Anionic Surfactants ◽  
High Conductivity ◽  
Nanocomposite Films ◽  
Benzenesulfonic Acid ◽  
Free Standing ◽  
Camphorsulfonic Acid ◽  
Doped Polymers ◽  
Polyaniline Nanocomposite

A versatile process employing anionic surfactants has been developed for the preparation of processible nanocomposite films with electrical conductivity and magnetic susceptibility. Maghemite (γFe2O3) nanoclusters (~10 nm in size) are coated with 4-dodecyl-benzenesulfonic acid, and polyaniline (PAn) chains are doped with 10-camphorsulfonic acid. The coated nanoclusters and doped polymers are soluble in common solvents, and casting the solutions readily gives free-standing nanocomposite films with nanocluster contents as high as ~50 wt %. The γFe2O3/PAn nanocomposites show high conductivity (82–237 S cm -1 ) and magnetizability (up to ~35 emu/g γFe2O3).

Fabrication of High Quality Poly-Si From Fluorinated Precursors

1993 ◽  
Vol 297 ◽  
Author(s):  
Shin-Ichi Ishihara ◽  
Deyan He ◽  
Tetsuya Akasaka ◽  
Yuzoh Araki ◽  
Isamu Shimizu
Keyword(s):  
Thin Films ◽  
Activation Energy ◽  
Electrical Conductivity ◽  
Thin Layer ◽  
Atomic Hydrogen ◽  
Solid Phase ◽  
Chemical Interaction ◽  
In Situ Observation ◽  
High Quality

Poly-Si thin films with grains 100–200 nm in dia. showing a highly ordered texture were grown from fluorinated precursors, SiFnHm (n+m=3), on a glass substrate at 300–400 °C with the aid of atomic hydrogen. According to the in situ observation by ellipsometry, the reconstruction was undergone in a solid phase stimulated by impinging atomic hydrogens within a thin layer of about 10 nm thick owing to the strong chemical interaction of the pair of H and F in Si-network. Both H and F were released efficiently from the network to the levels of 2 × 1020 cm−3 and (2−5) × 1019 cm−3, respectively. Dangling bonds were also efficiently passivated down to 4 × 1016 cm−3 with hydrogens diffused through the network. P-doped films showing electrical conductivity of 10−2 S/cm (300 °K) with the activation energy of 0.24 eV was obtained by alternately repeating the deposition of thin layer and the treatment with atomic hydrogens.

Preparation of YSZ Electrolyte for SOFC by Electron Beam PVD

2006 ◽  
Vol 317-318 ◽  
pp. 913-916 ◽  
Author(s):  
Tae Ho Shin ◽  
Ji Heang Yu ◽  
Shi Woo Lee ◽  
In Sub Han ◽  
Sang Kuk Woo ◽  
...  
Keyword(s):  
Activation Energy ◽  
Electrical Conductivity ◽  
Electron Beam ◽  
Vapor Deposition ◽  
Physical Vapor Deposition ◽  
Ionic Conduction ◽  
Yttria Stabilized Zirconia ◽  
Stabilized Zirconia ◽  
High Activation ◽  
Ysz Electrolyte

Yttria stabilized zirconia (YSZ) films with the thickness of up to 12 μm were prepared on alumina and NiO-YSZ substrates by electron beam physical vapor deposition (EB-PVD). The films showed nano-scaled columnar structures depending on the substrate temperature. Electrical conductivity of the YSZ films on alumina was also investigated at the temperature between 700 and 1000oC in oxidizing atmosphere. High activation energy of the conductivity (>1.03eV) indicated that the conduction via grain boundary controlled the ionic conduction in the films prepared by EB-PVD. La0.6Sr0.4CoO3-δ as a cathode was applied on the YSZ/NiO-YSZ in order to evaluate the performance of the YSZ electrolyte.

Conductivity Mechanisms in Acceptor Doped KTaO3 Crystals

1990 ◽  
Vol 210 ◽  
Author(s):  
T. Scherban ◽  
S.Q. Fu ◽  
A.S. Nowick
Keyword(s):  
Activation Energy ◽  
Electrical Conductivity ◽  
Oxygen Vacancy ◽  
Ionic Conduction ◽  
Electron Hole ◽  
Cu Doping ◽  
Hole Conduction ◽  
Protonic Conductors ◽  
Dry Conditions ◽  
Co Doped

AbstractThe electrical conductivity of perovskite—structured KTaO3 crystals acceptor doped with Co, Cu or Fe was investigated after treatments in oxidizing and reducing atmospheres under both wet and dry conditions. Isotope effect measurements (using H2O vs. D2O) show that, after treatments in wet gases of low P(O2), all the crystals are primarily protonic conductors, through a process of proton hopping with an activation energy close to 0.84 eV. Electron hole conduction dominatesat high P(O2) in the case of Fe and Cu doping. For Co—doped crystals, the conductivity is independent of P(O2) up to 1 atm., indicating that ionic conduction predominates. There is no evidence of oxygen vacancy migration, leading to the conclusion that the activation energy for that process Is relatively high.

scholarly journals In-Situ and Ion Implantation Nitrogen Doping on Near Stoichiometric a-SiC:H Films

2004 ◽  
Vol 1 (2) ◽  
pp. 26-30
Author(s):  
A. R. Oliveira ◽  
M. N. P. Carreño
Keyword(s):  
Activation Energy ◽  
Electrical Conductivity ◽  
Ion Implantation ◽  
Nitrogen Doping ◽  
Room Temperature ◽  
Chemical Vapor ◽  
Dark Conductivity ◽  
Implantation Technique ◽  
Electrical Conductivities

In this work we study the nitrogen n-type electrical doping of a-Si0.5C0.5:H films obtained by plasma enhanced chemical vapor deposition (PECVD) utilizing and comparing two doping techniques: in-situ (during the material growth) and ion implantation. The in-situ doped a-SiC:H films were obtained adding different amounts of N2 to the precursor gas mixture. For ion implantation four different nitrogen implanted concentrations were studied (between 1018 and 1021 atoms/ cm3) using multiple energies and doses to define a homogeneously doped layer. The doping experiments are carried out on a-SiC:H samples that present different structural order. The results show that high levels of electrical conductivity can be obtained with ion implantation technique. For in-situ technique the doping effect is also observed but must be improved in order to attain higher electrical conductivities. In the best case the room temperature dark conductivity for the sample implanted with 1021 nitrogens/cm3 was ~10-7 (Ω.cm)-1 and the activation energy was 0.2 eV. For in-situ doping the electrical dark conductivity reached values near 10-10 (Ω.cm)-1 at high temperatures and the activation energy was ~0.6 eV. Despite of the apparent low values of the electrical conductivity, these results are promising because we are dealing with a wide gap material and the doping processes are still not optimized.

Effect of Cu doping on the electrical Properties of ZnTe by Vacuum Thermal Evaporation

2018 ◽  
Vol 31 (3) ◽  
pp. 20
Author(s):  
Sarmad M. M. Ali ◽  
Alia A.A. Shehab ◽  
Samir A. Maki
Keyword(s):  
Activation Energy ◽  
Electrical Conductivity ◽  
Hall Effect ◽  
Carrier Concentration ◽  
Hall Mobility ◽  
Cu Doping ◽  
Before And After ◽  
Hall Effect Measurements ◽  
Evaporation Technique ◽  
P Type

In this study, the ZnTe thin films were deposited on a glass substrate at a thickness of 400nm using vacuum evaporation technique (2×10-5mbar) at RT. Electrical conductivity and Hall effect measurements have been investigated as a function of variation of the doping ratios (3,5,7%) of the Cu element on the thin ZnTe films. The temperature range of (25-200°C) is to record the electrical conductivity values. The results of the films have two types of transport mechanisms of free carriers with two values of activation energy (Ea1, Ea2), expect 3% Cu. The activation energy (Ea1) increased from 29meV to 157meV before and after doping (Cu at 5%) respectively. The results of Hall effect measurements of ZnTe , ZnTe:Cu films show that all films were (p-type), the carrier concentration (1.1×1020 m-3) , Hall mobility (0.464m2/V.s) for pure ZnTe film, increases the carrier concentration (6.3×1021m-3) Hall mobility (2m2/V.s) for doping (Cu at 3%) film, but  decreases by increasing Cu concentration.

scholarly journals Behavior and properties of water in silicate melts under deep mantle conditions

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Bijaya B. Karki ◽  
Dipta B. Ghosh ◽  
Shun-ichiro Karato
Keyword(s):  
Electrical Conductivity ◽  
Molar Volume ◽  
Water Solution ◽  
Pure Water ◽  
Electrical Conductance ◽  
Water Structure ◽  
Bulk Water ◽  
Silicate Melts ◽  
Pressure Regime ◽  
Low Pressures

AbstractWater (H2O) as one of the most abundant fluids present in Earth plays crucial role in the generation and transport of magmas in the interior. Though hydrous silicate melts have been studied extensively, the experimental data are confined to relatively low pressures and the computational results are still rare. Moreover, these studies imply large differences in the way water influences the physical properties of silicate magmas, such as density and electrical conductivity. Here, we investigate the equation of state, speciation, and transport properties of water dissolved in Mg1−xFexSiO3 and Mg2(1−x)Fe2xSiO4 melts (for x = 0 and 0.25) as well as in its bulk (pure) fluid state over the entire mantle pressure regime at 2000–4000 K using first-principles molecular dynamics. The simulation results allow us to constrain the partial molar volume of the water component in melts along with the molar volume of pure water. The predicted volume of silicate melt + water solution is negative at low pressures and becomes almost zero above 15 GPa. Consequently, the hydrous component tends to lower the melt density to similar extent over much of the mantle pressure regime irrespective of composition. Our results also show that hydrogen diffuses fast in silicate melts and enhances the melt electrical conductivity in a way that differs from electrical conduction in the bulk water. The speciation of the water component varies considerably from the bulk water structure as well. Water is dissolved in melts mostly as hydroxyls at low pressure and as –O–H–O–, –O–H–O–H– and other extended species with increasing pressure. On the other hand, the pure water behaves as a molecular fluid below 15 GPa, gradually becoming a dissociated fluid with further compression. On the basis of modeled density and conductivity results, we suggest that partial melts containing a few percent of water may be gravitationally trapped both above and below the upper mantle-transition region. Moreover, such hydrous melts can give rise to detectable electrical conductance by means of electromagnetic sounding observations.

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