The Defect Structure of BaTiO3 Thin Films

1993 ◽  
Vol 310 ◽  
Author(s):  
L.A. Wills ◽  
B.W. Wessels
Keyword(s):  
Thin Films ◽  
Cross Section ◽  
Defect Structure ◽  
Oxygen Vacancies ◽  
Vacuum Annealing ◽  
Deep Level ◽  
Energy Levels ◽  
The Other ◽  
Optical Cross Section ◽  
Impurity Defects

AbstractThe defect structure of BaTiO3 thin films grown on (100) Si was examined using transient photocapacitance spectroscopy. The concentration, optical cross section and associated energy levels of both native and impurity defects in as-grown and annealed BaTiO3 films were evaluated. Deep level defects withpeak energies of Ev+1.8, Ev+2.4, Ev+2.7, Ev+3.0-3.1 and Ev+3.2-3.3 eV were observed in the as-grown films. Upon vacuum annealing, the concentration of the traps at Ev+3.0 and Ev+3.2 eV increased while the concentration of the traps at Ev+ 1.8 and Ev+2.4 eV decreased. The levels at Ev+3.0-3.1 and Ev+3.2-3.3 eV are attributed to oxygen vacancies. The other levels are tentatively ascribed to Fe and Fe related defects.

scholarly journals EPR Spectroscopy of Different Sol Concentration Synthesized Nanocrystalline-ZnO Thin Films

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Manju Arora ◽  
Rayees A. Zargar ◽  
S. D. Khan
Keyword(s):  
Thin Films ◽  
Oxygen Vacancies ◽  
Film Surface ◽  
Epr Spectra ◽  
Zno Thin Films ◽  
Zno Films ◽  
Zno Film ◽  
Resonance Signal ◽  
X Ray ◽  
Impurity Defects

Nanocrystalline zinc oxide (nc-ZnO) thin films were grown on p-type silicon substrate through spin coating by sol-gel process using different sol concentrations (10 wt.%, 15 wt.%, and 25 wt.%). These films were characterized by high resolution nondestructive X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDS) attachment, and electron paramagnetic resonance (EPR) techniques to understand variations in structural, morphological, and oxygen vacancy with respect to sol concentration. The film surface morphology changes from nanowall to nanorods on increasing sol concentration. EPR spectra revealed the systematic variation from ferromagnetic to paramagnetic nature in these nc-ZnO films. The broad EPR resonance signal arising from the strong dipolar-dipolar interactions among impurity defects present in nc-ZnO film deposited from 10 wt.% sol has been observed and a single strong narrow resonance signal pertaining to oxygen vacancies is obtained in 25 wt.% sol derived nc-ZnO film. The concentrations of impurity defects and oxygen vacancies are evaluated from EPR spectra, necessary for efficient optoelectronic devices development.

Studies of Electrical Polarization Fatigue in SrBi2Ta2O9 Thin Films

1998 ◽  
Vol 541 ◽  
Author(s):  
K. M. Lee ◽  
D. Thomas ◽  
S. H. Kim ◽  
J. P. Maria ◽  
A. I. Kingon ◽  
...  
Keyword(s):  
Thin Films ◽  
Electrical Properties ◽  
Oxygen Vacancies ◽  
Remanent Polarization ◽  
Energy Levels ◽  
Bias Field ◽  
Charge Carriers ◽  
Temperature Dependent ◽  
Zero Bias ◽  
Electrical Polarization

AbstractThe polarization suppression and electrical properties directly associated with the electrical polarization fatigue in SrBi2Ta2O9system were systematically investigated using Pt/SBT/Pt capacitors. Three general observations were made after 109 switching cycles: (i) ∼95% of the remanent polarization was conserved, (ii) both high and zero bias field capacitance decreased, and (iii) leakage current density increased from approximately 10−7 to 10−5 A/cm2at ∼30kV/cm2. In addition, the “knee” field, at which the leakage abruptly increases, assumed smaller values with cumulative switching cycles. Temperature dependent leakage data was collected for both as-deposited and field-cycled samples. Based on these results, we propose the possibilities of enhanced concentration of charge carriers or additional reductions in interfacial conduction barriers. Motion of oxygen vacancies to less-shallow energy levels near electrode/ferroelectric interface may allow this mechanism to occur.

Characterization of Deep Levels in 3C-SiC by Optical-Capacitance-Transient Spectroscopy

2002 ◽  
Vol 719 ◽  
Author(s):  
Y. Nakakura ◽  
M. Kato ◽  
M. Ichimura ◽  
E. Arai ◽  
Y. Tokuda
Keyword(s):  
Cross Section ◽  
Thermal Activation ◽  
Deep Level ◽  
Threshold Energy ◽  
Thermal Activation Energy ◽  
Deep Levels ◽  
Optical Cross Section ◽  
Transient Spectroscopy ◽  
Capacitance Transient

AbstractAn optical-capacitance-transient spectroscopy (O-CTS) method was used to characterize the defects in 3C-SiC on Si. The O-CTS measurement enables us to estimate optical threshold energy and optical cross section for the defects. In the O-CTS spectrum, a peak was observed for photon energy hv larger than 0.5 eV. This peak was thought to be due to the ND1 center, which was also observed by deep level transient spectroscopy (DLTS) and found to have a thermal activation energy of 0.37 eV. The optical cross section for the center increased with hv for hv<0.6 eV and then decreased with increasing hv. The apparent optical threshold energy was about 0.47 eV. Another deep levels which have optical threshold energy of around 1.4 eV were also observed.

Sustained Coherent Epitaxy and Role of Oxygen Vacancies in La0.7Sr0.3MnO3􀀀 Thin Films Grown on SrTiO3 by Sputtering

2021 ◽  
Author(s):  
Mohamed Lmouchter ◽  
Minoru Suzuki
Keyword(s):  
Thin Films ◽  
Oxygen Vacancies ◽  
Lattice Mismatch ◽  
Spontaneous Magnetization ◽  
Rf Magnetron Sputtering ◽  
The Other ◽  
Epitaxial Thin Films ◽  
A Value ◽  
Curie Temperature Tc

Ferromagnetic La0.7Sr0.3MnO3 epitaxial thin films of single-crystal quality with very smooth surfaces are grown on SrTiO3 (100) substrates by on-axis rf magnetron sputtering. We find that the resistivity and the spontaneous magnetization for these 180 nm thick films are nearly equal to those of single crystals after thermal annealing. On the other hand, the Curie temperature TC is no higher than 270 K, a value far below the bulk one, which is quite unusual. As a clue to this riddle, we present a strong correlation between the lattice constant for these films and the amount of oxygen vacancies. From this, we conclude that the sustained coherent epitaxy takes place to match the lattice mismatch of 0.8% in the presence of a limited amount of oxygen vacancies, which relaxes the film in-plane stress while functions to significantly reduce TC.

A New Approach to the Demonstration of Oxidase-Localization Using Tannic Acid Or Catechin

1973 ◽  
Vol 31 ◽  
pp. 698-699
Author(s):  
V. Mizuhira ◽  
Y. Futaesaku
Keyword(s):  
Cross Section ◽  
Tannic Acid ◽  
Elastic Fiber ◽  
The Other ◽  
New Approach ◽  
Tissue Block ◽  
Active Reaction ◽  
The Cross

Previously we reported that tannic acid is a very effective fixative for proteins including polypeptides. Especially, in the cross section of microtubules, thirteen submits in A-tubule and eleven in B-tubule could be observed very clearly. An elastic fiber could be demonstrated very clearly, as an electron opaque, homogeneous fiber. However, tannic acid did not penetrate into the deep portion of the tissue-block. So we tried Catechin. This shows almost the same chemical natures as that of proteins, as tannic acid. Moreover, we thought that catechin should have two active-reaction sites, one is phenol,and the other is catechole. Catechole site should react with osmium, to make Os- black. Phenol-site should react with peroxidase existing perhydroxide.

Electron Irradiation Effects in Polyoxymethylene Crystals Grown Inside Trioxane Crystals

1971 ◽  
Vol 29 ◽  
pp. 78-79
Author(s):  
J. P. Colson ◽  
D. H. Reneker
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Detailed Examination ◽  
The Other ◽  
Electron Micrograph ◽  
Irradiation Effects ◽  
Threefold Axis ◽  
Typical Sample ◽  
Polymer Crystals ◽  
Chain Axis

Polyoxymethylene (POM) crystals grow inside trioxane crystals which have been irradiated and heated to a temperature slightly below their melting point. Figure 1 shows a low magnification electron micrograph of a group of such POM crystals. Detailed examination at higher magnification showed that three distinct types of POM crystals grew in a typical sample. The three types of POM crystals were distinguished by the direction that the polymer chain axis in each crystal made with respect to the threefold axis of the trioxane crystal. These polyoxymethylene crystals were described previously.At low magnifications the three types of polymer crystals appeared as slender rods. One type had a hexagonal cross section and the other two types had rectangular cross sections, that is, they were ribbonlike.

scholarly journals Generating Electricity from Natural Evaporation Using PVDF Thin Films Incorporating Nanocomposite Materials

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 585
Author(s):  
Ariel Ma ◽  
Jian Yu ◽  
William Uspal
Keyword(s):  
Thin Films ◽  
Graphene Oxide ◽  
Polyvinylidene Fluoride ◽  
Capillary Flow ◽  
Short Circuit ◽  
Current Source ◽  
Nanocomposite Materials ◽  
The Other ◽  
Pvdf Film ◽  
Ambient Conditions

Natural evaporation has recently come under consideration as a viable source of renewable energy. Demonstrations of the validity of the concept have been reported for devices incorporating carbon-based nanocomposite materials. In this study, we investigated the possibility of using polymer thin films to generate electricity from natural evaporation. We considered a polymeric system based on polyvinylidene fluoride (PVDF). Porous PVDF films were created by incorporating a variety of nanocomposite materials into the polymer structure through a simple mixing procedure. Three nanocomposite materials were considered: carbon nanotubes, graphene oxide, and silica. The evaporation-induced electricity generation was confirmed experimentally under various ambient conditions. Among the nanocomposite materials considered, mesoporous silica (SBA-15) was found to outperform the other two materials in terms of open-circuit voltage, and graphene oxide generated the highest short-circuit current. It was found that the nanocomposite material content in the PVDF film plays an important role: on the one hand, if particles are too few in number, the number of channels will be insufficient to support a strong capillary flow; on the other hand, an excessive number of particles will suppress the flow due to excessive water absorption underneath the surface. We show that the device can be modeled as a simple circuit powered by a current source with excellent agreement between the theoretical predictions and experimental data.

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