Silicon surface oxidation

Fig. 16.9. STM topograph of a partially oxidized silicon surface. With the sample biased at +2 V relative to the tip, the unoccupied states of a Si(lll)-7 X7 surface exposed to 0,2 L of O2 at 300 K is obtained. (Reproduced from Avouris, Lyo, and Bozso, 1991, with permission.)...

TFSA satisfies all these requirements for hydrophilic silicone surfaces. Using silica as a model for extensively oxidized silicone surfaces, we showed that silylation with vapor phase TFSA took place at room temperature under scrupulously dry conditions. In contrast, others have found for the more conventional silylating agents, the methylchlorosilanes and the methylmethoxy-silanes, that no reaction occurred at temperature below 200°C under similar dry conditions [38]. 

Covalent binding of amino, carboxy, and nitro-substituted aminopropyltriethoxysilanes to oxidized silicon surfaces and their interaction with octadecanamine and octadecanoic acid studied by X-ray photoelectron spectroscopy and ellipsometry... 

Figure 1. Generation of oxidized silicon surfaces carrying covalently linked functionalized silanes.

X-Ray photoelectron spectroscopic data on the functionalized silane-bound oxidized silicon surfaces and the guest molecule-treated surfaces formed from them... 

Fig. 12 Illustration outlining MIP film fabrication. The C-terminus nonapeptide epitope is attached through a tether to a glass or oxidized silicon surface by the N-terminal amino acid of the peptide. Monomers are photochemically cross-linked while remaining in contact with the peptide modified surface. Following polymerization, the glass substrate is removed. The protein can now bind to the MIP via its C-terminus nonapeptide epitope. Modified from [114]...

FIGURE 6.2 Height equivalent to a theoretical plate (H) of a GC-separated compound versus average carrier gas velocity for a 3-m-long silicon channel coated with non-polar dimethyl polysiloxane stationary phase (a) native silicon surface (b) oxidized silicon surface. Plots A are for hydrogen carrier gas, and plots B are for air carrier gas [598]. Reprinted with permission from the American Chemical Society. 

One of the key problems in the functionalization of silicon via solution methods is the possibility of unwanted side reactions, most notably oxidation. Silicon surfaces are known to be highly susceptible to oxidation. XPS spectra of even carefully prepared surfaces invariably show a significant Ols... 

Another approach in generating molecular insulating layers without the need of chemical conversion after deposition is the use of preliminarily modified molecules which can form dense self-assembled monolayers. To create dense self-assembled monolayers with sufficient robustness and insulating properties, a modified alkyltrichlorosilane with an aromatic end-group (18-phenoxyoctadecyl)tri-chlorosilane (PhO-OTS chemical structure Fig. 6.15a) was synthesized and tested [50]. The SAMs were created in a one-step process from vapor phase or solution. On self-assembly on a natively oxidized silicon surface the n-n interaction between the phenoxy end-groups of adjacent molecules creates an intermolecular top-link, leading to a more closely packed surface compared to monolayer than when linear end groups are used. 

Gamma-Globulin-Coated Oxidized Silicon Surfaces... 

The Behavior of Albumin in Plasma at the Oxidized Silicon Surface. A chance for albumin to be adsorbed out of plasma, not yet encountered on any of the materials tested, could be provided by removing fibrinogen and some globulins from competition. Some normal intact plasma was... 

Fibrinogen and 7s Gamma-Globulins at the Oxidized Silicon Surface... 

N. Takano, N. Hosoda, T. Yamada, andT. Osaka, Effect of oxidized silicon surface on chemical deposition of nickel on n-type silicon wafer, Electrochim. Acta 44, 3743, 1999. 

Precisely this latter situation arises if the confining solid surface is endowed with a chemical pattern that is both nanoscopic in size and hnite in extent. Such chemical patterns may be created by lithographic methods [179]. Atomic beams have been employed to produce hexagonal nemostruc-tures [180]. Other methods capable of creating cliemically nanostnictured substrate surfaces involve microphase separation in diblock copolymer films [181] or the use of forc( microscopy to locally oxidize silicon surfaces [182]. 

Lateral ordering of dots by self-assembly on nanostructured oxidized silicon surfaces... 

TOF-SIMS spectra obtained from silicon surfaces (from Ref. 11). A. Silicon treated with HF solution before polymer deposition. B. Oxidized silicon surface - no HF treatment. 

Equation (7.2) expresses the net minority-carrier density/unit area as the product of the bulk minority-carrier density/unit volume nj/Ns, with the depth of the minority-carrier distribution diNv multiplied in turn by the customary Boltzmann factor exp(g(0s — Vs)/kT) expressing the enhancement of the interface density over the bulk due to lower energy at the interface. The depth diNv is related to the carrier distribution near the interface using the approximation (valid in weak inversion) that the minority-carrier density decays exponentially with distance from the oxide-silicon surface. In this approximation, diNv is the centroid of the minority-carrier density. For example, for a uniform bulk doping of 10 dopant ions/cm at 290 K, using Eq. (7.2) and the surface potential at threshold from Eq. (7.7) (0th = 0.69 V), there are Qp/q = 3 x 10 charges/cm in the depletion layer at threshold. This Qp corresponds to a diNv = 5.4 nm and a carrier density at threshold of JVinv = 5.4 x 10 charges/cm. ... 

Y. Manassen, R.J. Hamers, J.E. Demuth, A.J. Castellano Jr., Direct observation of the precession of individual paramagnetic spins on oxidized silicon surfaces, Phys. Rev. Lett. 62 (1989) 2531. 

Bohanon T, Blender G, Knoll W et al. Neural cell pattern formation on glass and oxidized silicon surfaces modified with poly(N-isopropylacrylamide). J Biomater Sci 1996 8 19-39. 

Similar results were observed with the uptake and release of an anionic surfactant into and from poly(NIPAM-co-2VP) microgel particles [36]. A comparison has also been made between the effect of added CPC on the hydrodynamic diameter of the free microgel particles in dispersion and the thickness, as determined from ellipso-metry measurements, of deposited monolayers of the same microgel particles on cationically-modified, oxidized silicon surfaces. The behavior of the microgel layers reflects the dispersion properties of the particles in the presence of CPC [35]. 

According to our experimental results [37], selectivity may be achieved by gas-phase catalyst delivery [38 0] on lithographically machined planar and nonplanar templates consisting of oxidized silicon surfaces. Our bottom-up fabrication approach is easy to carry out, scalable to large areas, and compatible with standard silicon microfabrication technology. In this specific CVD process, nanotube structures are designed and built first on planar patterns composed of SiOa and Si most of the substrates used in this study were Si(lOO) wafers capped with a lOO-nm-thick silica layer, however, below we discuss the case of thick silica layers (up to 8.5 M-m). 

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