Silane deposition procedure

Alkyl chains are generally deposited on the silica surface using the corresponding alkylsilane. The hydride intermediate route, developed by Sandoval and Pesek78,79 gives an alternative for this method. The one-step alkylsilane route, is replaced by a two-step silanization-alkylation procedure. The loss of process simplicity is compensated by the advantages of an increased alkyl density and enhanced coating stability. 

Probe measurements in silane discharges have been reported [296,297]. Apparently, no difficulties were experienced, as the deposited amorphous silicon layer on the tip was sufficiently photoconductive. For typical silane discharge conditions values for are found to be between 2 and 2.5 eV. Electron densities are around 1 x 10 cm - [296]. Probe measurement in the ASTER system failed due to strong distortions of the probe current, even after following cleaning procedures. 

A range of procedures have been described for the silanization of glass, including approaches employing both elevated and room-temperature organic phase, aqueous phase, vapor phase, and chemical vapor deposition of the silane. However, little has been published with regard to the rehability and... 

Alkaline-cleaned substrate. After alkaline cleaning, the steel substrate was completely devoid of aliphatic fatty acids, as was verified by TOFSIMS. The freshly cleaned substrate was immediately immersed in the 1% silane solution and analyzed. The wettability of the cleaned steel by the solution was considerably improved by the alkaline cleaning procedure. The spectra obtained with a film deposited from a pH 10.5 solution are shown in Fig. 7. A rigorous peak identification procedure was applied here. The masses of all major peaks could be... 

The CSC precursor build-up has been studied after modification of the silica gel surface from the gas phase. This gas phase modification involves the deposition of one molecular layer at the time. For thicker coatings, a cyclic procedure is needed. Liquid phase modification of the silica surface may also yield valuable ceramic precursors. The precursor molecular structure and layer thickness is controlled by other parameters compared to gas phase procedures. Parameters such as reaction solvent, silane concentrations and presence of water are of primal importance. Those have been discussed in detail in chapter 9. In this chapter, the application of silica modified with aminosilanes, will be discussed. The aminopropylsilica is used as a prototype compound for the production of ceramics by liquid phase chemical surface coating. 

Jonas and coworkers deposited gold nanoparticles on silane-functionalized silica inverse opals prepared by the codeposition procedure. The gold/sihca hybrid inverse opals shown in Fig. 3a were then formed within the macrop-orous silica network by electroless deposition of HAuCU with hydroxylamine hydrochloride [35]. 

A dielectric oxide layer such as silica is useful as shell material because of the stability it lends to the core and its optical transparency. The thickness and porosity of the shell are readily controlled. A dense shell also permits encapsulation of toxic luminescent semiconductor nanoparticles. The classic methods of Stober and Her for solution deposition of silica are adaptable for coating of nanocrystals with silica shells [864,865]. These methods rely on the pH and the concentration of the solution to control the rate of deposition. The natural affinity of silica to oxidic layers has been exploited to obtain silica coating on a family of iron oxide nanoparticles including hematite and magnetite [866-870]. The procedures are mostly adaptations of the Stober process. Oxide particles such as boehmite can also be coated with silica [871]. Such a deposition process is not readily extendable to grow shell layers on metals. The most successful method for silica encapsulation of metal nanoparticles is that due to Mulvaney and coworkers [872—875]. In this method, the smface of the nanoparticles is functionalized with aminopropyltrimethylsilane, a bifunctional molecule with a pendant silane group which is available for condensation of silica. The next step involves the slow deposition of silica in water followed by the fast deposition of silica in ethanol. Changes in the optical properties of metal nanoparticles with silica shells of different thicknesses were studied systematically [873 75]. This procedure was also extended to coat CdS and other luminescent semiconductor nanocrystals [542,876-879]. 

The propensity of halosilanes to react with hydroxy-rich surfaces, including silanol terminated glass surfaces, enables layers to be deposited. Terminal functional groups on the absorbed silanes can react with complementary functions on the chromophore allowing the formation of a mono-layer. The procedure can be iterated (Fig. 2.9) [38 0]. 

SiOx Deposition by Plasma Polymerization. ThePETfilm(110mmwide)ran between the electrode A and B and was set up on reels of the rolling machine. Two positions where the PET film between the electrode A and B were used for the SiOx deposition. One position was within a 5 mm distance from the electrode B surface (deposition on the electrode surface), and the other position was in the midpoint between the electrode A and B (30 mm far from the electrode B surface). The silane was poured into a reservoir and air dissolved in the silane was removed by a repeated freezing-fusion procedure. The reservoir was kept in temperature-controlled oven at 60X1 to increase the vapor pressure of the silane. 

Choice of Silanes for SiOx Film Deposition. Plasma polymerization of silanes results in plasma polymer films which contain carbonaceous components such as Si-C and CH2-CH2 groups within SiOx networks. In order to form SiOx networks without the carbonaceous components, carbonaceous components should be excluded from the deposited SiOx films. Many researchers have followed a heating procedure for the elimination of the carbonaceous components from the deposited SiOx films but this procedure is not applicable to SiOx-deposited PET films because of poor thermal-resistance of the film. In this study, a silane that was suitable for the SiOx deposition with less carbonaceous component was investigated. Five silanes, TEOS, TrEOS, TMOS, DMDMOS, and TMS, which contained different C/Si atomic ratio of 8 to 4 and different bond structure (Si-O-C and Si-C bonds) between Si and C atoms, were used for the plasma polymerization. Table I compares file C/Si atomic ratio in the deposited SiOx films from the five silanes. The C/Si atom ratio in the deposited SiOx films, as shown in Table I, depends on the C/Si atomic ratio and the bond structure in the starting silanes Silanes with a small C/Si atom ratio deposit SiOx films with a low carbon content, and silanes with Si-O-C bonds also deposit SiOx films with a low carbon content. From this viewpoint, TMOS is preferable to TEOS, TrEOS, DMDMOS, and TMS as a silane for SiOx deposition with a less carbonaceous component, although TMOS is not yet a satisfactory material for the SiOx deposition. The SiOx film deposited from TMOS reveals a C/Si atom ratio of 1.5. 

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