Temperature effect on dielectric behavior of an industrial porcelain-type ceramic

2009 ◽  
Vol 87 (9) ◽  
pp. 973-980
Author(s):  
O. Hachicha ◽  
N. Ghorbel ◽  
A. Kallel ◽  
Z. Fakhfakh
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Charge Trapping ◽  
Dielectric Behavior ◽  
Mirror Image ◽  
Induced Current ◽  
Physical Mechanisms ◽  
Motion Process ◽  
Influence Of Temperature On ◽  
Scanning Electron

For a better understanding of the physical mechanisms involved in insulators submitted to electron irradiation inside a scanning electron microscope, it is important to investigate charge trapping and detrapping. The commonly used technique to deduce the trapping ability and the motion process of electric charges is based on two complementary experimental methods: the scanning electron microscope mirror effect (SEMME) and the induced current measurement (ICM). In this paper, our study is devoted to the influence of temperature on the behavior of porcelain materials during electron injection time. To evaluate the geometry of the trapped charge distribution, a detailed analysis using the mirror image formation and its evolution is developed.

scholarly journals The Beam Current Considerations in SEM Accordance to Mirror Effect Phenomenon

2013 ◽  
Vol 15 ◽  
pp. 70-75 ◽  
Author(s):  
Hassan N. Al-Obaidi ◽  
Imad H. Khaleel
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Theoretical Investigation ◽  
Electric Potential ◽  
Mathematical Expression ◽  
Beam Current ◽  
Mirror Image ◽  
Mirror Effect ◽  
Scanning Electron

A theoretical investigation have been presented to exploring the influence of electrons beam current on the electron mirror image deduced inside the scanning electron microscope (SEM). A rough mathematical expression for the electric potential that associated with electron beam is derived. The results clearly shows that the beam current could be used to enhance or conversely deteriorate the phenomena of mirror effect. So this work procedure may consider to be tool controllable of this phenomena for investigation purposes.

Microcharacterization of Induced Electric Fields in Poorly Conducting Specimens Irradiated in an Environmental Scanning Electron Microscope

2001 ◽  
Vol 7 (S2) ◽  
pp. 786-787
Author(s):  
Marion A. Stevens-Kalceff
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Electric Fields ◽  
High Vacuum ◽  
Charge Trapping ◽  
Environmental Scanning Electron Microscope ◽  
Variable Pressure ◽  
Environmental Scanning ◽  
Excess Charge ◽  
Scanning Electron

In a conventional scanning electron microscope, a thin, grounded conductive coating is applied to specimens that are poor electrical conductors to prevent retarding and deflection of the incident electron beam. in a variable pressure or environmental scanning electron microscope (ESEM), excess charge on the surface of uncoated poorly conducting specimens is balanced using ionized environmental gas. Ionized gas in environmental mode and grounded conductive coatings in conventional or high vacuum mode minimize charging at the specimen surface, however significant charge trapping may still occur in the implanted sub-surface regions of poorly conducting materials. A small fraction (<10-6) of the incident electrons are trapped at irradiation induced or pre-existing defects within the irradiated specimen. The trapped charge induces a highly localized electric field which can result in electro-migration and micro-segregation of charged mobile defect species within the irradiated micro-volume of specimen.

Contrast formation mechanisms in the environmental scanning electron microscope

1999 ◽  
Vol 5 (S2) ◽  
pp. 274-275
Author(s):  
M. Toth ◽  
M.R. Phillips
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Charge Trapping ◽  
Sample Surface ◽  
Environmental Scanning Electron Microscope ◽  
Hydride Vapor Phase Epitaxy ◽  
Environmental Scanning ◽  
Formation Mechanisms ◽  
Electron Dose ◽  
Scanning Electron

Uncoated, non-conductive samples can be imaged and analyzed in the environmental scanning electron microscope (ESEM) due to effective charge neutralization at the sample surface by ionized gas molecules. Under some gas pressure and electron dose conditions, ESEM images of uncoated, poorly conductive samples often contain contrast not present in secondary or backscattered electron images of the (coated) samples obtained in conventional SEMs. It has been proposed that the contrast is related to charge trapping at defects and impurities. It has also been suggested that UV cathodoluminescence (CL) may contribute to contrast in the ESEM. In this paper, we present experimental evidence of contrast formation in the ESEM due to charge trapping in Dy doped zircon, electron trapping at oxygen vacancies in sapphire and the absence of signal generation by 360nm UV CL.The specimens used in this study were (i) cross-sectioned Titanium in-diffusion doped sapphire single crystal, (ii) Dy doped synthetic Zircon7 and (iii) 43 μm epitaxial GaN grown on c-pane sapphire by hydride vapor phase epitaxy.

Experimental study of polymethyl methacrylate: damage under corona discharge

2018 ◽  
Vol 82 (3) ◽  
pp. 31301
Author(s):  
Nora Kireche ◽  
Sébastien Rondot ◽  
Ferroudja Bitam-Megherbi ◽  
Omar Jbara ◽  
Mickael Gilliot ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Corona Discharge ◽  
Polymethyl Methacrylate ◽  
Electron Irradiation ◽  
Degradation Mechanism ◽  
Dielectric Behavior ◽  
Chemical Degradation ◽  
Surface Damages ◽  
Scanning Electron

In high-voltage applications, insulators may be exposed to corona discharges during long periods. In this experimental work, corona discharge tests of different durations are carried out in air at atmospheric pressure on polymethyl methacrylate (PMMA) samples. The resulting surface degradation is studied with several techniques. The surface damages are observed with environmental scanning electron microscope and atomic force microscopy. The results show that electrical trees occur on the surface of material and their distribution depends on the corona discharge duration. The chemical changes on PMMA surface are analyzed by Fourier transform infrared spectroscopy and a chemical degradation mechanism is proposed. Evolution of surface resistivity with corona aging is also implemented by using a classical I(V) method. In addition, to study the dielectric behavior of PMMA, the monitoring of kinetics of the trapped charge under electron irradiation in a scanning electron microscope is performed. The charging ability of PMMA under electron irradiation and its time constant of charging decrease with electrical aging.

Dependence on crystallographic orientation of trapping properties in a polished MgO single crystal

2002 ◽  
Vol 80 (3) ◽  
pp. 285-289
Author(s):  
N Dammak ◽  
A Kallel ◽  
Z Fakhfakh ◽  
D Tréheux
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Crystallographic Orientation ◽  
Charge Trapping ◽  
Dislocation Network ◽  
Experimental Characterization ◽  
Space Charges ◽  
Scanning Electron ◽  
Crystallographic Orientations

It is well known that the presence of space charges in an insulator is correlated with electric breakdown. Many studies have been carried out on the experimental characterization of space charges and on phenomenological models of trapping and detrapping. In this paper, we outline the dependence on crystallographic orientations of the charge-trapping phenomenon in polished MgO. The charging phenomenon was characterized during and after electron injection by using a scanning electron microscope (SEM). It was shown that the trapping ability depends on the dislocation network of different crystallographic orientations. PACS No.: 72.20Jv

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