scholarly journals Role of charged defects on the electrical and electromechanical properties of rhombohedralPb(Zr,Ti)O3with oxygen octahedra tilts

2016 ◽  
Vol 93 (1) ◽  
Author(s):  
Tadej Rojac ◽  
Silvo Drnovsek ◽  
Andreja Bencan ◽  
Barbara Malic ◽  
Dragan Damjanovic
Keyword(s):  
Oxygen Octahedra ◽  
Electromechanical Properties ◽  
Charged Defects

On the Role of Charged Defect States and Deep Traps in the Photocarrier Drift and Diffusion in a-Si:H

2000 ◽  
Vol 609 ◽  
Author(s):  
Paul Stradins ◽  
Akihisa Matsuda
Keyword(s):  
Particle Number ◽  
Defect States ◽  
Total Electron ◽  
Minority Carrier Diffusion Length ◽  
Continuity Equations ◽  
Effective Mobility ◽  
Almost All ◽  
Charged Defects ◽  
And Diffusion

ABSTRACTThe drift and diffusion in the presence of charged defects and photocarriers trapped in the tail states is re-examined. In continuity equations, diffusive and drift currents are related to free particles while the Poisson equation includes all charges. In order to make use of ambipolar diffusion approximation, the mobilities and diffusion coefficients should be attributed to the total electron and hole populations making them strongly particle-number dependent. Due to the asymmetry of the conduction and valence band tails, almost all trapped electrons reside in negatively charged defects (D−). A simple model of photocarrier traffic via tail and defect states allows to establish the effective mobility values and coefficients in Einstein relations. In a photocarrier grating experiment, grating of D− is counterbalanced by the grating of trapped holes. Nevertheless, electrons remain majority carriers, allowing the measurement of minority carrier diffusion length, but analysis is needed to relate the latter with μτ product.

Diffusion Mechanisms in Sige Alloys

1999 ◽  
Vol 568 ◽  
Author(s):  
Arthur F.W. Willoughby ◽  
Janet M. Bonar ◽  
Andrew D.N. Paine
Keyword(s):  
Diffusion Processes ◽  
Dopant Diffusion ◽  
Elemental Silicon ◽  
Self Diffusion ◽  
Si Substrates ◽  
Marker Layer ◽  
Diffusion Mechanisms ◽  
Silicon And Germanium ◽  
Charged Defects

ABSTRACTInterest in diffusion processes in SiGe alloys arises from their potential in HBT's, HFET's, and optoelectronics devices, where migration over distances as small as a few nanometres can be significant. Successful modelling of these processes requires a much improved understanding of the mechanisms of self- and dopant diffusion in the alloy, although recent progress has been made. It is the purpose of this review to set this in the context of diffusion processes in elemental silicon and germanium, and to identify how this can help to elucidate behaviour in the alloy. Firstly, self diffusion processes are reviewed, from general agreement that self-diffusion in germanium is dominated by neutral and acceptor vacancies, to the position in silicon which is still uncertain. Germanium diffusion in silicon, however, appears to be via both vacancy and interstitial processes, and in the bulk alloy there is evidence for a change in dominant mechanism at around 35 percent germanium. Next, a review of dopant diffusion begins with Sb, which appears to diffuse in germanium by a mechanism similar to self-diffusion, and in silicon via monovacancies also, from marker layer evidence. In SiGe, the effects of composition and strain in epitaxial layers on Si substrates are also consistent with diffusion via vacancies, but questions still remain on the role of charged defects. The use of Sb to monitor vacancy effects such as grown-in defects by low temperature MBE, are discussed. Lastly, progress in assessing the role of vacancies and interstitials in the diffusion of boron is reviewed, which is dominated by interstitials in silicon-rich alloys, but appears to change to domination by vacancies at around 40 percent germanium, although studies in pure germanium are greatly needed.

scholarly journals Role of Nanotechnology in Reinforcement of Polymers

2021 ◽  
pp. 57-61
Author(s):  
Munish Baboria ◽  
Priya Devi
Keyword(s):  
Theoretical Work ◽  
Nano Particles ◽  
Photovoltaic Devices ◽  
Electromechanical Properties ◽  
Future Expectations ◽  
Sic Nanoparticles ◽  
Sensitive Sensor ◽  
Basic Technology ◽  
Mechanical Devices

Nanotechnology with feasible engineering became a universal technique producing applications in different fields. Nanotechnology use variety of manipulating approach but the consequences and result are innovatory and much bigger then revolutionary. Nanotechnology is now known by many capabilities by using different materials, compositions, and structure on a molecular scale. From the electro-mechanical devices to the medical applications, all these theoretical work is now developed or in construction and with innovative progressing as well. Considering all these, it is clear that the nano tech approach is feasible and optimum and ready to mark the mark. Here we discuss the basic technology behind this and how it is used for the reinforcement of different materials in different cases and their usage. For example, use of Carbon Nanatubes(CNT) or the Silicon carbide (Sic) nanoparticles to give strength, stability or desired electromechanical properties whereas titanium dioxide and Gold Nano particles are good radiation absorbers (fall types)while used as photovoltaic devices and sensitive sensor respectively, This is the highest achievements and future expectations which include different fields s like automobile, aerospace metallurgy, electronics etc.

Piezoelectric Composites Based on Hydroxyapatite / Barium Titanate

2008 ◽  
Vol 54 ◽  
pp. 1-6 ◽  
Author(s):  
Chris R. Bowen ◽  
K.V.S. Raman ◽  
Vitaly Yu. Topolov
Keyword(s):  
Volume Fraction ◽  
Active Material ◽  
Ferroelectric Ceramic ◽  
Ceramic Composites ◽  
Batio3 Ceramic ◽  
Physical Factors ◽  
Electromechanical Properties ◽  
Modified Model ◽  
Perovskite Type

This paper reports experimental and modelling results on the manufacture and properties of hydroxyapatite / BaTiO3 ceramic composites and studies their electromechanical properties with ferroelectric ceramic volume fractions, mFC ³ 0.7. In these composites the bio-active properties of hydroxyapatite are combined with the electromechanical properties of a perovskite-type ferroelectric BaTiO3 ceramic in an attempt to create a novel polarised bone-substitute material. Experimental results of the volume fraction dependences of the effective piezoelectric coefficients * 31 d (mFC), * 33 d (mFC) and dielectric permittivity e *s 33 (mFC) of stress free samples are analysed within the framework of a modified model of a porous piezo-active material that is described in terms of 1–3 (one-dimensional rods in a continuous matrix) and 2–2 connectivity (laminates). The role of several structural elements and physical factors in forming the electromechanical properties of the composites is discussed. It is shown that performance of these materials typical properties are 5 pC / N < | * 31 d |< 45 pC / N, 20 pC / N < * 33 d < 100 pC / N and 400 < e *s 33 / 0 e < 1300.

The Role of Charged Defects in Photo-Degradation of Hydrogenated Amorphous Silicon

1992 ◽  
Vol 258 ◽  
Author(s):  
Vikram L. Dalal ◽  
Sanjiv Chopra ◽  
Ralph Knox
Keyword(s):  
Optical Absorption ◽  
Amorphous Silicon ◽  
Hydrogenated Amorphous Silicon ◽  
Rapid Decay ◽  
Photo Degradation ◽  
Photo Conductivity ◽  
Charged Defects ◽  
Hydrogenated Amorphous ◽  
Kinetics Of

ABSTRACTWe examine the role of charged defects in inducing degradation of electronic properties of a-Si:H upon exposure to light. We measure the kinetics of decay of photo-conductivity of a-Si:H films at different light intensities, and the corresponding changes in mid-gap optical absorption. We find that the initial, rapid decay of photo-conductivity can be modeled guite well by invoking Adler's model of conversion of charged defects to neutral dangling bonds(D- to D° conversion). A consequence of this conversion is a decrease in sub-gap absorption upon photo-induced degradation, which we observe. Therefore, we conclude that charged defects coexist with neutral defects in a-Si:H, and they play a major role in early stages of photo-degradation.

scholarly journals Investigation of Local Conduction Mechanisms in Ca and Ti-Doped BiFeO3 Using Scanning Probe Microscopy Approach

Nanomaterials ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 940
Author(s):  
Maxim S. Ivanov ◽  
Vladimir A. Khomchenko ◽  
Maxim V. Silibin ◽  
Dmitry V. Karpinsky ◽  
Carsten Blawert ◽  
...  
Keyword(s):  
Transport Properties ◽  
Scanning Probe Microscopy ◽  
Domain Walls ◽  
Scanning Probe ◽  
Ferroelectric Ceramics ◽  
Probe Microscopy ◽  
Charge Imbalance ◽  
Order Of Magnitude ◽  
Charged Defects

In this work we demonstrate the role of grain boundaries and domain walls in the local transport properties of n- and p-doped bismuth ferrites, including the influence of these singularities on the space charge imbalance of the energy band structure. This is mainly due to the charge accumulation at domain walls, which is recognized as the main mechanism responsible for the electrical conductivity in polar thin films and single crystals, while there is an obvious gap in the understanding of the precise mechanism of conductivity in ferroelectric ceramics. The conductivity of the Bi0.95Ca0.05Fe1−xTixO3−δ (x = 0, 0.05, 0.1; δ = (0.05 − x)/2) samples was studied using a scanning probe microscopy approach at the nanoscale level as a function of bias voltage and chemical composition. The obtained results reveal a distinct correlation between electrical properties and the type of charged defects when the anion-deficient (x = 0) compound exhibits a three order of magnitude increase in conductivity as compared with the charge-balanced (x = 0.05) and cation-deficient (x = 0.1) samples, which is well described within the band diagram representation. The data provide an approach to control the transport properties of multiferroic bismuth ferrites through aliovalent chemical substitution.

Low-frequency electrostatic defect mode in doped pair-ion plasmas

2010 ◽  
Vol 76 (3-4) ◽  
pp. 607-616 ◽  
Author(s):  
I. KOURAKIS ◽  
N. S. SAINI
Keyword(s):  
Density Ratio ◽  
Low Frequency ◽  
Defect Mode ◽  
Nonlinear Effects ◽  
Acoustic Oscillations ◽  
Pair Plasma ◽  
Electron Positron ◽  
Charged Component ◽  
Charged Defects

AbstractThe nonlinear amplitude modulation dynamics of electrostatic oscillations of massive charged defects in a three-component pair plasma is investigated, i.e. doped pair-ion plasmas (anticipating the injection of a massive charged component in the background, e.g. in fullerene experiments). Ion-acoustic oscillations in electron-positron-ion (e-p-i) plasmas are also covered, in the appropriate limit. Linear and nonlinear effects (MI, envelope modes) are discussed. The role of the temperature and density ratio between the pair species is stressed.

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