Contamination oxide removal

Fig. 10.6 A p-type Si wafer with a 20 nm thick thermal oxide has been contaminated by scratching the backside with metal wires (Ni, Cu, Fe), according to the pattern shown in (a) and later annealed at 1200°C for 30 s. (e) Under cathodic bias in acetic acid, oxide defects become decorated by hydrogen bubbles. (c, d) After oxide removal junction defects caused by metal precipitates are decorated by hydrogen bubbles, if sufficient catho...

ShallowTray air strippers are low-profile, transportable units for removal of volatile contaminants from aqueous waste streams and potable water supplies. Air strippers do not destroy contaminants but transfer them to the airstream, where they can be destroyed by incineration or oxidation, removed by activated carbon, or released into the atmosphere if relevant emissions criteria are met. 

TerraTherm Environmental Services, Inc., a subsidiary of Shell Technology Ventures, Inc., has developed the in situ thermal desorption (ISTD) thermal blanket technology to treat or remove volatile and semivolatile contaminants from near-surface soils and pavements. The contaminant removal is accomplished by heating the soil in sim (without excavation) to desorb and treat contaminants. In addition to evaporation and volatilization, contaminants are removed by several mechanisms, including steam distillation, pyrolysis, oxidation, and other chemical reactions. Vaporized contaminants are drawn to the surface by vacuum, collected beneath an impermeable sheet, and routed to a vapor treatment system where contaminants are thermally oxidized or adsorbed. 

Amines. Triethylamine (TEA) (Pennsalt and Eastman), like all tertiary alkylamines, is subject to light-catalyzed air oxidation. These contaminants are removed readily along with moisture by passing through a column of (or standing over) freshly activated silica gel. (Note molecular sieves must not be used here—these seem to accelerate decomposition and color formation.) The amine should be dry and colorless before use. Other amines used in this work were obtained from Eastman and purified by distillation immediately before use. 

The plutonium metal feed stock contained about 5 ppm natural lead which was not removed by the process. Recovery of americium in the finishing process (oxalate precipitation and calcination) averaged 98.5%. Most of the residual chromium contaminant was removed from the oxalate in decanted supernate and washes. The finished oxide product purity exceeded specifications i.e., >95% Am02 By selective blending, impurities in the shipped product, predominantly lead and nickel, were kept below 2%. 

Chapter 2 considers the removal of inorganic water contaminants using photocatalysis. Metal cations react via one-electron steps first leading to unstable chemical intermediates, and later to stable species. Three possible mechanisms are identified (a) direct reduction via photo-generated conduction band electrons, (b) indirect reduction by intermediates generated from electron donors, and (c) oxidative removal by electron holes or hydroxyl radicals. The provided examples show the significance of these mechanisms for the removal of water contaminants such as chromium, mercury, lead, uranium, and arsenic. 

The procedure for preparing atomically smooth, hydrogen-terminated silicon surfaces involves a number of steps removal of hydrocarbon contamination, formation of a uniform oxide, oxide removal, etching of the silicon surface, and the formation of the passivation layer. The uniformity of the oxide is important in developing a smooth surface at the Si/Si02 interface. 

An experiment that evaluated the necessity of oxide removal as a step in cleaning was performed (19)-Contaminated wafers were cleaned using the two sequence of SPM, HF, APM, HPM or SPM, APM, HPM. Table I gives the SIMS results that were obtained. 

Cadmium [7440-43-9] M 112.4, m 321.1 , b 767 , df 8.642. Any oxide contaminant is removed by filtering the molten metal, under vacuum, through quartz wool. Its solubility in Hg is 5.2% (18°), and it is soluble in mineral acids. [Wagenknecht Juza in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol II p 1092 7965.]... 

Fine colloidal or soluble inorganic contaminants are removed from water by physical-chemical methods of waste water cleaning. The main methods used are coagulation, oxidation, sorption, extraction and electrolysis methods. 

Reddy and Karri (2008b) also reported research investigating Fenton-like oxidation coupled with EK remediation of low-permeabiUty soils contaminated with both heavy metals and PAHs. That study examined the simultaneous oxidation of organic contaminants and removal of heavy metals. Kaolin spiked with nickel and phenanthrene each at a concentration of 500mg/kg of dry soil to represent typical heavy metal and PAH contaminants found at contaminated sites. Four-week lab-scale EK... 

Another possible application is the clean-up of industrially contaminated soil. Removal of organics by both carbon dioxide and water under supercritical conditions is being considered. A further possibility is extraction by supercritical water followed by oxidation as part of the same process. Compounds of very high molecular weight may be involved and solubility studies are needed [30]. 

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