Oxide layers removal

A quartz round flask was used as an electrochemical cell with three electrodes. Al-wires (Alfa, 99.999%) were used as reference and counter electrodes. Mild steel sheets were employed as working electrodes. The working electrodes were mechanically polished with emery paper, cleaned with acetone in an ultrasonic bath, treated with dilute hydrochloric acid and rinsed with distilled water. Prior to the electrodeposition process the electrodes were anodically polarized in the employed ionic liquid to remove as far as possible the native oxide layer. Removal of the... 

Equipment selection and debugging of an oxide-layer-removal technology... 

It was expected that, because the contamination products were concentrated within the surface oxide layer, removal of the latter would eliminate radioactive contamination. Steel samples with oxide layers up to 100 pm in width were processed [1]. 

The studied time parameters of laser emission varied from continuous mode to nanosecond pulse-length range. According to theoretical estimates [2] confirmed by experimental investigations, thin oxide layers can be removed from surfaces most efficiently under the impacts of nanosecond-length pulses. It is the mechanism of thermal-impact oxide-layer removal that is realized in such a case due to rapid... 

As the result of performed investigation the following peculiarities of the oxide-layer-removal process were discovered ... 

This is illustrated in Fig. 1 the oxidation was carried out at a pressure of approximately 10" mm and at 900°C, at this temperature the oxide is volatile thus a pit is formed. Fig. 2 shows oxidation at a similar pressure on ill material although there are fewer oxidation pits in this picture, they are not found at dislocation sites. Oxidation in concentrated nitric acid had the advantage that the oxide layer left by the CP4 etch that was used to remove the damaged layer could be removed by HF. Many more oxide particles were formed on surfaces that did not have this oxide layer removed prior to oxidation. Thus we can say, at least for germanium, that the dislocations do not act as preferential sites for the nucleation of oxidation. 

Figure 5.11 AFM images of PS-i)-P4VP-[Re(DIAN)(C0)3]+C10j spin-coated on different substrate surfaces (film thickness = 40 nm) (a) silicon wafer modified with (3-aminopropyl)trimethoxysilane (b) silicon wafer modified with A-trimethoxysilylpropyl-AyV,lV-trimethylammonium chloride (c) silicon wafer modified with 3-(p-methoxyphenyl)propyltrichlorosilane and (d) silicon wafer with native oxide layer removed. All the films were prepared from toluene solution. Scan size (a)- c) 1X1 pm (d) 500 X 500 nm. (From Cheng and Chan.71 Reprinted with permission. Copyright 2005 American Chemical Society.)...

Silicon oxide layer removal Photoresist removal... 

For some materials, the most notable being silicon, heating alone sufiBces to clean the surface. Commercial Si wafers are produced with a thin layer of silicon dioxide covering the surface. This native oxide is inert to reaction with the atmosphere, and therefore keeps the underlying Si material clean. The native oxide layer is desorbed, i.e. removed into the gas phase, by heating the wafer in UHV to a temperature above approximately 1100 °C. This procedure directly fonus a clean, well ordered Si surface. 

Fig. 9. Fabrication sequence for an oxide-isolated -weU CMOS process, where is boron and X is arsenic. See text, (a) Formation of blanket pod oxide and Si N layer resist patterning (mask 1) ion implantation of channel stoppers (chanstop) (steps 1—3). (b) Growth of isolation field oxide removal of resist, Si N, and pod oxide growth of thin (<200 nm) Si02 gate oxide layer (steps 4—6). (c) Deposition and patterning of polysihcon gate formation of -source and drain (steps 7,8). (d) Deposition of thick Si02 blanket layer etch to form contact windows down to source, drain, and gate (step 9). (e) Metallisation of contact windows with W blanket deposition of Al patterning of metal (steps 10,11). The deposition of intermetal dielectric or final...

So far, we have been talking in our case study about the advantage of an oxide layer in reducing the rate of metal removal by oxidation. Oxide films do, however, have some disadvantages. 

To fully understand the formation of the N13S2 scale under certain gas conditions, a brief description needs to be given on the chemical aspects of the protective (chromium oxide) Ci 203/(nickel oxide) NiO scales that form at elevated temperatures. Under ideal oxidizing conditions, the alloy Waspaloy preferentially forms a protective oxide layer of NiO and Ci 203 The partial pressure of oxygen is such that these scales are thermodynamically stable and a condition of equilibrium is observed between the oxidizing atmosphere and the scale. Even if the scale surface is damaged or removed, the oxidizing condition of the atmosphere would preferentially reform the oxide scales. 

Sodium and potassium are restricted because they react with sulfur at elevated temperatures to corrode metals by hot corrosion or sulfurization. The hot-corrision mechanism is not fully understood however, it can be discussed in general terms. It is believed that the deposition of alkali sulfates (Na2S04) on the blade reduces the protective oxide layer. Corrosion results from the continual forming and removing of the oxide layer. Also, oxidation of the blades occurs when liquid vanadium is deposited on the blade. Fortunately, lead is not encountered very often. Its presence is primarily from contamination by leaded fuel or as a result of some refinery practice. Presently, there is no fuel treatment to counteract the presence of lead. 

Water hammer results from the collapse of this trapped steam. The localized sudden reduction in pressure caused by the collapse of the steam bubbles has a tendency to chip out pipe and tube interiors. Oxide layers that otherwise would resist further corrosion are removed, resulting in accelerated corrosion. 

A piece of sodium metal stored under kerosene m a metal container is removed from ajar and blotted with dry napkin or filter paper With a sharp knife, the layer of oxides IS removed until a shiny surface appears The removed layer is then destroyed carefully by adding very small pieces (not larger than 0 5 cm) to precooled 200 mL of methanol or ethanol... 

With special techniques for the activation of the metal—e.g. for removal of the oxide layer, and the preparation of finely dispersed metal—the scope of the Refor-matsky reaction has been broadened, and yields have been markedly improved." The attempted activation of zinc by treatment with iodine or dibromomethane, or washing with dilute hydrochloric acid prior to use, often is only moderately successful. Much more effective is the use of special alloys—e.g. zinc-copper couple, or the reduction of zinc halides using potassium (the so-called Rieke procedure ) or potassium graphite. The application of ultrasound has also been reported. ... 

First spray the dried chromatogram homogeneously with reagent 1. Then remove excess reagent in a stream of cold air in the fume cupboard (ca. 30 min for silica gel and 3 h for aluminium oxide layers). Then spray the chromatogram lightly with reagent 2. 

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