Silicon material characterization

Research of biologically active silicone materials continues. The synthesis and characterization of polysiloxanes having bioactive pendant groups,556 557 and the preparation of bioactive porous organic-inorganic hybrids for medical applications,558 have been reported. 

The characterization of what can be considered as material properties is part of any routine in the studies of new polymers. Thus, any major research paper on new silicone materials should be accounted for in this section. And that is, unfortunately, impossible. 

Etch pit formation as a result of the factors given in 1-4 above can be used to characterize silicon materials. A summary of common defect etchants for silicon is given in Table 2.1. 

Other forms of silica, such as pyrogenic silica and mineral opals are normally nonporous. Pyrogenic silica is composed of silica particles with a very narrow particle size distribution. This material is obtained by vaporizing Si02 in an arc or a plasma jet, or by the oxidation of silicon compounds [152], Artificial opals are materials characterized by the presence of Si02 microspheres [16]. 

Figure 3-8 Raman microprobe spectrum of fluorinated hydrocarbon contaminant on silicon wafer that had been polished and plasma-etched (lower) and Raman spectrum of polytetrafluoro-ethylene (upper). Laser, 135 mW at 514.5 nm. Slits, 300 jon. Time, 0.5 s per data point. (Reproduced with permission from Adar, F., in Microelectronics Processing Inorganic Materials Characterization (L. A. Casper, ed.), ACS Symposium Series Vol. 295, pp. 230-239. American Chemical Society, Washington, D.C., 1986. Copyright 1986 American Chemical Society.)...

The areas of inorganic and organic positron chemistry deal mainly with material characterization and industrial applications using PAS. Both chemical and electronic industries have found PAS to be a powerful method. In addition to the traditional solution chemistry of the positron and Ps [11], PAS has been developed to determine the free volume Bom-Oppenheimer approximation, such as molecular solids [14] and polymers [15]. The unique localization property of Ps in free volumes and holes has opened new hope in polymer scientific research that determination of atomic-level free volumes at the nanosecond scale of motion is possible. During the last ten years, most positron annihilation research has involved a certain amount of polymer chemistry, polymers and coatings, which will be discussed in Chapters 12 and 13. For inorganic systems, oxides are mostly studied using the positron and Ps. Silicon oxides and zeolites are the most important systems in positron and Ps chemistry. The developments in this area have on the cavity structure and chemical states of inner surfaces. Chapters 8 and 14 will discuss this subject. 

In recent years one observes a growing industrial demand for organosilicon materials having properties, which can not be found in conventional polymers. These also include silicone fluids, characterized by high refraction indices, such as -1.50, utilized extensively in personal care applications. An important class of such systems are siloxanes having phenylethenyl type substituents along polymer backbone (Fig. 1). 

Major new insights into the surface science of silicone materials were catalyzed by the work of deGennes, whose theories of polymer wetting and adhesion have inspired many to explore his provocative themes [7]. These explorations focused attention on the need for a polymeric material that is well characterized, liquid over a wide molecular weight range, with controlled molecular weight distribution and crosslinkable in a controlled fashion. Dimethylpolysiloxane is the best available candidate and has become central to a revolution in polymer surface physics. 

In this example, a pentacene film was thermally evaporated to 50 nm thick on the native oxide of a room temperature silicon wafer. NEXAFS spectroscopy was performed on this film at the NIST/Dow soft x-ray materials characterization facility at the national synchrotron light source (NSLS) of Brookhaven National Laboratory. The carbon K-edge was collected at several incident angles, shown in Figure 4.2.5. 

Material characterization technique which uses a tip (typically silicon) on the end of a cantilever... 

As a characterization tool for porous silicon materials and devices, gas adsorption-desorption analysis has proved to be extremely useful, particularly so for process development. 

Khokhlov A (2008) Nanoporous silicon structural characterization using NMR and applications. Ph.D. thesis, University of Leipzig. Available on-line at http //uni-leipzig.de/ valiu/index.php option=com content view=artiele id=30 Itemid=28 Klobes P, Meyer K, Munro RG (2006) Porosity and specific surface area measurements for solid materials, NIST reeommended practiee guide. Special Publication 960-17 (Sept 2006)... 

AFM is one of the newest techniques for the characterization of surface morphology. The information provided by AFM does not duplicate that of SEM but is generally quite complementary. SEM photos can be used to study surface features that are several tenths of a nanometer while the resolution of AFM is less than 0.1 nm. Therefore, AFM has the ability to distinguish objects on smooth surfaces of molecular dimensions. In fact, under optimum conditions atomic force microscopy has been able to attain resolution on the atomic scale. The highest resolution is achieved for surfaces such as pure metals used for electrodes or for silicon materials used in semiconductor devices. 

Material characterization technique which uses a tip (typically silicon) on the end of a cantilever to determine the surface profile of a material. As the cantilever is moved across the surface, a laser is reflected off of the backside. As the cantilever is deflected, the change in laser beam position is detected by a photodetector. This information is then used to create a three-dimensional image of the surface, with atomic-scale resolution. 

Pieters BE (2008) Characterization of thin-film silicon materials and solar cells through numerical modelling. PhD Thesis, Delft University of Technology, Delft... 

The application of Raman spectroscopy to the study of semiconductors is an area of interest with a long history from the perspective of both QC and failure analysis. The general applicability of Raman spectroscopy to semiconductors is covered in depth in Chapter 12 and has been the subject of a number of articles and reviews [154-157]. During the last 10 years, the opportunity to move beyond the research Raman microscopes for materials research to Raman analyzers for QC analysis has been explored. Some of the major areas of interest from a quality control/failure analysis standpoint are contamination, defect identification, materials characterization, and strain mapping at interfaces (between components and between silicon and attached circuitry). 

Camir6, C. L., Saint-Jean, S. J., Mochales, C., Nevsten, R, Wang, J. S., Lidgren, L., McCarthy, 1., and Ginebra, M. P. 2006. Material characterization and in vivo behavior of silicon substituted alpha-tricalcium phosphate cement. 76B 424-31. 

The use of the silicone materials is indicated due to the possibility of producing flexible FSSs, with the important implication of making FSS elements with a complex shape. Then, the principal characterizations of these iimovative materials are ... 

Camire CL, Saint-Jean SJ, Mochales C et al. (2006) Material characterization and in vivo behavior of silicon substituted a-tricalcium phosphate cement. J Biomed Mater Res B Appl Biomater 76B 424-431 Kokubo T, Ito S, Huang ZT et al. (IWO) Ca-P-rich layer formed on high-strength bioactive glass-ceramics A-W. J Biomed Mater Res 74 331-343... 

Silicon carbide (SiC) is a strong, microwave-absorbing, chemically inert ceramic material characterized by high... 

The chapter presents the current state of knowledge on silicone nanostructures such as solid nanoparticles, empty nanocapsules, and ultra-thin polymeric films. The methods of their preparation and characterization, as well as their application are presented. It has been shown that the silicone nanostructures are mainly fabricated in the sol-gel processes from silicone precursors containing groups, which are reactive under acidic or basic conditions. These reactive groups include alkoxysilyl (=Si-0-R), silanol (=Si-OH), or Si-H bonds. The silicone materials are formed in the polymerization and/or polycondensation processes. The process of precursor transformation to silicone polymeric materials is often described as solidification. ... 

The development of novel silicone material requires extensive characterization in order to estabhsh the structure and property relationship. The spectroscopic techniques such as FTIR, Raman, XPS, NMR, and SIMS could complement each other md provide vcduable insight of materials chemistry. The hcud to find spectroscopic assignments of silicones have been detailed in this chapter. This chapter briefly summcuized the utihzation of spectroscopic techniques on sihcone coatings, biomaterials and other advanced silicone materials. The emergence of new 2D correlation studies being conducted in material science have been deemed to enhance the screening capability of these spectroscopic techniques. 

Subambient thermal volatilization analysis can also be used to probe the effects of physical fillers in silicone materials. In 2008 Lewicki et al. [51] studied the degradation profiles and product speciation of a series of montmorillonite clay filled silicone elastomers which had been characterized using SATVA. Shown in Figure 13.17 are a series of TVA thermal degradation profiles for the non-oxidative degradation of a bimodal-condensation-cured silicone matrix, filled with 0-8 wt% of organically modified montmorillonite (0-MMT) exfoliated nanoclay platelets. 

Presented in this chapter is a review of silicone materials used as biomaterials and in tissue engineering. The types, synthesis and properties of these silicone materials for biomedical applications are discussed. The chapter also discusses the various surface modification and characterization techniques used for improving the biocompatibihty of sUicone materials. Finally, we discuss our work on the cellular behavior of human dermal fibroblasts cultured on silicone scaffold materials. 

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