Silicon electrodeposition

EDX analysis of the deposits did not reveal any other compound than Si, meaning that the deposit purity is assumed to be better than 99.9%. 

The role of the substrate is also to be considered as far as the nuclei wrist depends on the physical interaction energy at the beginning of the electrolysis pulse. 

Here the concern is to recover silicon from Si-Fe compounds by dissolving only silicon from this compound used as anode and recovering pure Si at the cathode of the electrorefiner. Three steps are necessary to prove the process feasibility  

Mechanism of the anodic dissolution providing Si in the electrolytic bath 

Current efficiency and purity of the silicon recovered at the cathode. 

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J. M. Olson and K. Carleton, Kinetics of silicon electrodeposition, in Silicon Material Preparation and Economical Wafering Methods, R. Lutwack and A. Morrison (eds.), p. 261, Noyes Publications, 1985. 

Borissenko N, Abedin SZE, Endres F (2006) In situ STM investigation of gold reconstruction and of silicon electrodeposition on Au(lll) in the room temperature ionic liquid 1-butyl-l-methylpyrroUdinium his(trifluoromethylsulfonyl)imide. J Phys Chem B 110 6250-6256... 

Metals of a useful quality can clearly be electrodeposited. The extent to w hich electrodeposition can be used in the formation of semiconductors is not yet clear. Examples of silicon electrodeposition are few and generally result in amorphous deposits [2-5], Pourbaix diagrams [6] suggest that Si is far from stable in water, the most desirable medium for electrodeposition, although Ge may be tractable. 

Fig. 6.2-23 (a) In situ STM picture of an about 100 nm thick film (600 nm x 200 nm) (b) in situ current/voltage tunneling spectra of HOPG (curve 1) and of the silicon electrodeposit (curve 2) on HOPG. 

Fig. 12.1 SEM micrographs of silicon electrodeposits obtained from 0.15 M SiCLi in (a) [C4mPyr][Cp3S03], (b) [C4mPyr][N(Tf)2], and (c) [C4mPyr][FAP] at 100 °C...

Dolgyi A, Bandarenka H, Prischepa S, Yanushkevich K, Nenzi P, Balucani M, Bondarenko V (2012) Electrochemical deposition of Ni into mesoporous silicon electrodeposition of metals on restricted substrates. ECS Trans 41 111... 

Cohen U (1977) Some prospective applications of silicon electrodeposition from molten fluorides to solar cell fabrication. J Electron Mater 6 607-643... 

Elwell D, Feigelson RS, Rao GM (1983) The morphology of silicon electrodeposits on graphite substrates. J Electrochem Soc 130 1021-1025... 

Concerning silicon electrodeposition, considering basic properties and cost, it is demonstrated here that the best solvent is NaF-KF. 

In the 1980s, silicon electrodeposition in molten salts was considered an attractive option for SoG-Si production. Elwell et al. [92-94, 96, 97] studied the electrochemical deposition of Si from fluoride melts. They concluded that only molten KF-LiF and LiF-NaF-KF could be used to obtain good quality deposits. 

More systematic studies of silicon electrodeposition began in the 1930 s with Dodero s (17)(18) investigation of the electrolysis of molten silicates at temperatures of 800 to 1250 0. The very high potentials used in these studies would be expected to liberate not only silicon but also alkali and alkaline earth metals. There is no conclusive proof in Dodero s work that silicon was the primary cathode product or the result of a reduction of the silicon containing compounds by alkali or alkaline earth metals that had been produced by electrolysis. His best result was 72% silicon produced from a melt composition of 5 Si02 -1 Na20 - 0.2NaF electrolyzed at 1150 C. 

The main problem in using the Hall process for silicon electrodeposition is that silicon melts at a much higher temperature than aluminum (1412°C compared to 660°C). Cryolite can not be used at this temperature due to volatization problems, so a binary or ternary melt containing SiOg had to be developed that would be stable above this temperature. Johnson (29) indicated that calcium and magnesium based silicate melts looked favorable, while other alkaline earth and alkali metal silicates were less desirable. 

A more complete discussion of silicon electrodeposition can be found in Elweil and Rao (49). 

A wide range of applications for hard, wear-resistant coatings of electroless nickel containing silicon carbide particles have been discussed by Weissenberger . The solution is basically for nickel-phosphorus coatings, but contains an addition of 5-15 g/1 silicon carbide. Hiibner and Ostermann have published a comparison between electroless nickel-silicon carbide, electrodeposited nickel-silicon carbide, and hard chromium engineering coatings. 

Les composes mono- et disubstitues envisages ici sont utilises comme agents stabilisateurs du PVC ou comme catalyseurs dans la production de peintures par electrodeposition (enduits pour vehicules automobiles), d elastomeres de silicone, de revetements en poudre ou de polyurethanes ou encore comme catalyseurs d ester-ification. 

On the other hand, Xiao et al. [215] reported that smooth, dense, and erystalline PbTe films with nearly stoichiometric composition could be obtained by an optimized electrodeposition process from highly acidic (pH 0) tellurite solutions of uncomplexed Pb(II), on Au-coated silicon wafers. The results from electroanalyti-cal studies on Te, Pb, and PbTe deposition with a Pt rde at various temperatures and solution compositions supported the induced co-deposition scheme. The microstructure and preferred orientation of PbTe films was found to change significantly with the deposition potential and electrolyte concentration. At -0.12 V vs. Ag/AgCl(sat. KCl), the film was granular and oriented preferentially in the [100] direction. At potentials more negative than -0.15 V, the film was dendritic and oriented preferentially in the [211] direction (Pig. 3.13). 

Fisher JM, Berlouis LEA, Sawers LJM, MacDonald SM, Affrosman S, Diskett DJ, Astles MG (1994) Growth and characterization of electrodeposited films of cadmium telluride on silicon. J Cryst Growth 138 86-93... 

Jackson F, Berlouis LEA, Rocabois P (1996) Layer-by-layer electrodeposition of cadmium telluride onto silicon. J Cryst Growth 159 200-204... 

Sugimoto Y, Peter LM (1995) Cathodic electrodeposition of CdTe on n-type monocrystalline silicon. J Electroanal Chem 381 251-255... 

Early measurements of " Th were on seawater samples and Th was co-precipitated from 20-30 L of seawater with iron hydroxide (Bhat et al. 1969). This procedure may not recover all of the " Th in the sample, and an alpha emitting Th isotope (e g., °Th or Th) is added as a yield monitor. Following chemical purification of the Th fraction by ion exchange chromatography, the Th is electrodeposited onto platinum or stainless steel planchets. The planchets are then counted in a low background gas-flow beta detector to measure the beta activity and subsequently with a silicon surface barrier detector to determine the alpha activity of the yield monitor. The " Th activity is thus determined as ... 

Cerisier et al examined copper electrodeposits over a range of scales from 6 nm to 10 pm [78], They obtained a = 0.33 and j> = 0.46 for deposition on silicon from pyrophosphate solution, and concluded that growth occurs at three dimensional centers with little surface diffusion. 

It may be considered a fortunate coincidence that this book is published at the time of the introduction of copper interconnection technology in the microelectronics industry. In 1998 the major electronic manufacturers of integrated circuits (ICs) are switching from aluminum conductors produced by physical methods (evaporation) to copper conductors manufactured by electrochemical methods (electrodeposition). This revolutionary change from physical to electrochemical techniques in the production of microconductors on silicon is bound to generate an increased interest and an urgent need for familiarity with the fundamentals of electrochemical deposition. This book should be of great help in this crucial time. 

Radioactivity of uranium can be measured by alpha counters. The metal is digested in nitric acid. Alpha activity is measured by a counting instrument, such as an alpha scintillation counter or gas-flow proportional counter. Uranium may be separated from the other radioactive substances by radiochemical methods. The metal or its compound(s) is first dissolved. Uranium is coprecipitated with ferric hydroxide. Precipitate is dissolved in an acid and the solution passed through an anion exchange column. Uranium is eluted with dilute hydrochloric acid. The solution is evaporated to near dryness. Uranium is converted to its nitrate and alpha activity is counted. Alternatively, uranium is separated and electrodeposited onto a stainless steel disk and alpha particles counted by alpha pulse height analysis using a silicon surface barrier detector, a semiconductor particle-type detector. 

Our next example deals with thin hlms of TTF[Ni(dmit)2]2 grown by electrodeposition on silicon wafers (de Caro et al., 2004). We recall here that TTF[Ni(dmit)2]2... 

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