impurity

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impurity

Electronics a small quantity of an element added to a pure semiconductor crystal to control its electrical conductivity
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005

impurity

[im′pyu̇r·əd·ē]
(science and technology)
An undesirable foreign material in a pure substance.
(solid-state physics)
A substance that, when diffused into semiconductor metal in small amounts, either provides free electrons to the metal or accepts electrons from it.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
ARB medications that contain impurities above the published interim acceptable limits continue to be recalled, with certain exceptions.
"While the total exposure to these impurities for most patients was small, we are deeply concerned that patients were exposed to this impurity in the first place and that the presence of nitrosamines went undetected for a period of time," the FDA said in a statement.
to check impurities. They should impose fine on violation of cotton
Scientific testing has shown that aniline impurities are toxic to humans, causing skin allergies, damage to major organs and genetic defects, as well as being linked to cancer.
"This is true for the bio, moisture, and water-related impurities that effect the dielectric constant of the fuel.
Along with confirmation of the (obvious) regulated amount of active ingredient, inclusion of product-based related compounds and process-based impurities can cause issue with overall drug efficacy, safety and stability.
The aim of the control strategy is to track impurities that may contaminate pharmaceutical products where there is potential for contamination by multiple different sources.
Impurities of boron and aluminum are used to form p-regions in structures based on 4H-SiC by means of ion implantation or thermal diffusion.
Three responses were measured for each experiment: resolution (Rs) between impurity E and F ([y.sub.1]), Rs between Impurity G and SIM ([y.sub.2]), and Rs between impurities B and C ([y.sub.3]).
However, as it can be observed in the literature [1, 8-12], the TlBr detector limitations are not yet completely resolved: primarily, the low collection efficiency of charge carriers, a fact that is probably caused by impurities and defects created in the crystal growth or in the surface treatment process.
Research on theoretical and experimental aspects of [sup.18]F production using small cyclotrons has been carried out elsewhere to study the optimum target system and irradiation parameters [13], radioactive by-products in the cyclotron vicinity [14], and identification of radioactive impurities [15].