scholarly journals Improved space charge suppression in PP/SEBS nanocomposites by controlling MgO nanoparticles with abundant surface defects

2019 ◽  
Vol 115 (10) ◽  
pp. 102904 ◽  
Author(s):  
Qi Cheng ◽  
Jun-Wei Zha ◽  
Jin-Tao Zhai ◽  
Dong-Li Zhang ◽  
Xingming Bian ◽  
...  
Keyword(s):  
Space Charge ◽  
Surface Defects ◽  
Mgo Nanoparticles

Surface defect chemistry of Y-substituted and hydrated BaZrO3 with subsurface space-charge regions

2016 ◽  
Vol 4 (19) ◽  
pp. 7437-7444 ◽  
Author(s):  
Jonathan M. Polfus ◽  
Tor S. Bjørheim ◽  
Truls Norby ◽  
Rune Bredesen
Keyword(s):  
Surface Layer ◽  
Space Charge ◽  
Space Charge Region ◽  
First Principles ◽  
Surface Defect ◽  
Surface Defects ◽  
Defect Chemistry ◽  
First Principles Calculations ◽  
Proton Conducting ◽  
Charged Species

First-principles calculations were utilized to elucidate the complete defect equilibria of surfaces of proton conducting BaZrO3, encompassing charged species adsorbed to the surface, defects in the surface layer as well as in the subsurface space-charge region and bulk.

scholarly journals Interplay between H2O and CO2 coadsorption and space-charge on Y-doped BaZrO3 surfaces

2018 ◽  
Vol 6 (48) ◽  
pp. 24823-24830 ◽  
Author(s):  
Jonathan M. Polfus ◽  
Jing Yang ◽  
Bilge Yildiz
Keyword(s):  
Surface Chemistry ◽  
Space Charge ◽  
First Principles ◽  
Crucial Role ◽  
Surface Defects ◽  
First Principles Calculations

Crucial role of coadsorption, surface defects and subsurface space-charge on the surface chemistry of oxides is demonstrated by first-principles calculations.

scholarly journals The Effect of Particle Size on the Optical and Electronic Properties of MgO Nanoparticles

2021 ◽  
Author(s):  
Martijn Zwijnenburg
Keyword(s):  
Particle Size ◽  
Surface Defects ◽  
Binding Energies ◽  
Edge States ◽  
Many Body ◽  
Mgo Nanoparticles ◽  
Optical Gap ◽  
Optical And Electronic Properties ◽  
Many Body Perturbation Theory ◽  
Effect Of Particle Size

The (band) edge states, fundamental gaps, optical gaps, exciton binding energies and UV-Vis spectra for a series of cuboidal nanoparticles of the prototypical oxide magnesium oxide (MgO), the largest of with has 216 atoms and edges of 1 nm, were predicted using many-body perturbation theory (ev<i>GW</i>-BSE). The evolution of the properties with particle size was explicitly studied. It was found that while the edge states and fundamental gap change with particle size, the optical gap remains essentially fixed for all but the smallest nanoparticles, in line with what was previously observed experimentally. The explanation for these observations is demonstrated to be that while the optical gap is associated with an exciton that is highly localised around the particle’s corner atoms, the edge states, while primarily localised on the magnesium corner atoms ­(electron) and oxygen corner atoms (hole), show significant delocalisation along the edges. The strong localisation of the exciton associated with the optical gap on the corner atoms is argued to also explain why the nanoparticles have a much smaller optical gaps and red-shifted spectra than bulk MgO. Finally, it is discussed how this non-quantum confinement behaviour, where the properties of the nanoparticles arise from surface defects rather than differences in localisation of edge or exciton states, appears typical of alkaline earth oxide nanoparticles, and that the true optical gap of bulk crystals of such materials is also probably the result of surface defects, even if unobservable experimentally. <br>

Current-voltage characteristics in organic semiconductor crystals: space charge vs. contact-limited carrier transport

2004 ◽  
Vol 846 ◽  
Author(s):  
J. Reynaert ◽  
V. I. Arkhipov ◽  
J. Genoe ◽  
G. Borghs ◽  
P. Heremans
Keyword(s):  
Space Charge ◽  
Carrier Transport ◽  
Surface Defects ◽  
Experimental Studies ◽  
Surface States ◽  
Organic Crystal ◽  
Striking Difference ◽  
Carrier Injection ◽  
Semiconductor Crystals ◽  
Current Voltage

ABSTRACTNumerous experimental studies, mostly based on the time-of flight (TOF) technique, showed that the conductivity in organic crystals can be analysed in terms of (trap-controlled) band transport. However, recent comparative studies of TOF signals and space charge limited currents (SCLCs) in tetracene crystals revealed a striking difference in carrier mobilities estimated from TOF current transients and from SCLC curves. The analysis of the SCLC curves yielded the mobilities wildly varying within 6 orders of magnitude. Therefore, it is not always clear whether the measured current-voltage (IV) device characteristics are controlled by charge injection or by transport in the bulk. In this work, we formulate a model of dopant-assisted carrier injection across a metal/organics interface and use this model for the analysis of IV curves measured on a tetracene and perylene crystal. The model suggests the occurrence of an energetically disordered layer at the surface of an organic crystal. This might be either an amorphous phase of the same material or a crystalline layer with a high density of defects and/or impurities. Since, at variance with bulk properties, the surface of an organic crystal is poorly controlled and can be strongly modified upon the contact deposition, the model of injection-controlled IV characteristics can explain the striking difference between the TOF mobility and the apparent ‘SCLC mobility’ measured in tetracene crystals. In order to give more credence to the role of surface defects states in the dark charge transport, we compare IV characteristics measured on sandwich and coplanar structures. In the latter structure, surface states show a major contribution to the conductivity.

Defects in Crystals

1968 ◽  
Vol 26 ◽  
pp. 244-245
Author(s):  
Kenneth R. Lawless
Keyword(s):  
Electron Microscope ◽  
Point Defects ◽  
Surface Defects ◽  
Chemical Properties ◽  
Material Point ◽  
Crystal Defects ◽  
Defects In Crystals ◽  
Irradiation Effects ◽  
Normal Lattice ◽  
Line Defects

One of the most important applications of the electron microscope in recent years has been to the observation of defects in crystals. Replica techniques have been widely utilized for many years for the observation of surface defects, but more recently the most striking use of the electron microscope has been for the direct observation of internal defects in crystals, utilizing the transmission of electrons through thin samples.Defects in crystals may be classified basically as point defects, line defects, and planar defects, all of which play an important role in determining the physical or chemical properties of a material. Point defects are of two types, either vacancies where individual atoms are missing from lattice sites, or interstitials where an atom is situated in between normal lattice sites. The so-called point defects most commonly observed are actually aggregates of either vacancies or interstitials. Details of crystal defects of this type are considered in the special session on “Irradiation Effects in Materials” and will not be considered in detail in this session.

Characterization of homoepitaxial diamond films by Electron microscopy

1991 ◽  
Vol 49 ◽  
pp. 880-881
Author(s):  
D.P. Malta ◽  
S.A. Willard ◽  
R.A. Rudder ◽  
G.C. Hudson ◽  
J.B. Posthill ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Surface Defects ◽  
Substrate Surface ◽  
Diamond Films ◽  
Chemical Vapor ◽  
Polycrystalline Diamond ◽  
Large Degree ◽  
Rf Plasma ◽  
Semiconducting Diamond

Semiconducting diamond films have the potential for use as a material in which to build active electronic devices capable of operating at high temperatures or in high radiation environments. A major goal of current device-related diamond research is to achieve a high quality epitaxial film on an inexpensive, readily available, non-native substrate. One step in the process of achieving this goal is understanding the nucleation and growth processes of diamond films on diamond substrates. Electron microscopy has already proven invaluable for assessing polycrystalline diamond films grown on nonnative surfaces.The quality of the grown diamond film depends on several factors, one of which is the quality of the diamond substrate. Substrates commercially available today have often been found to have scratched surfaces resulting from the polishing process (Fig. 1a). Electron beam-induced current (EBIC) imaging shows that electrically active sub-surface defects can be present to a large degree (Fig. 1c). Growth of homoepitaxial diamond films by rf plasma-enhanced chemical vapor deposition (PECVD) has been found to planarize the scratched substrate surface (Fig. 1b).

Electron holography of interfaces in electroceramics

1993 ◽  
Vol 51 ◽  
pp. 1088-1089
Author(s):  
Vinayak P. Dravid ◽  
V. Ravikumar ◽  
Richard Plass
Keyword(s):  
Space Charge ◽  
Direct Evidence ◽  
Materials Science ◽  
Theoretical Work ◽  
Electron Holography ◽  
Resolution Limit ◽  
Interference Phenomenon ◽  
X Ray ◽  
Electron Sources ◽  
Science Community

With the advent of coherent electron sources with cold field emission guns (cFEGs), it has become possible to utilize the coherent interference phenomenon and perform “practical” electron holography. Historically, holography was envisioned to extent the resolution limit by compensating coherent aberrations. Indeed such work has been done with reasonable success in a few laboratories around the world. However, it is the ability of electron holography to map electrical and magnetic fields which has caught considerable attention of materials science community.There has been considerable theoretical work on formation of space charge on surfaces and internal interfaces. In particular, formation and nature of space charge have important implications for the performance of numerous electroceramics which derive their useful properties from electrically active grain boundaries. Bonnell and coworkers, in their elegant STM experiments provided the direct evidence for GB space charge and its sign, while Chiang et al. used the indirect but powerful technique of x-ray microchemical profiling across GBs to infer the nature of space charge.

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