Chemical vapor deposition 260 INDEX

Inside" processes—such as modified chemical vapor deposition (MCVD) and plasma chemical vapor deposition (PCVD)—deposit doped silica on the interior surface of a fused silica tube. In MCVD, the oxidation of the halide reactants is initiated by a flame that heats the outside of the tube (Figure 4.8). In PCVD, the reaction is initiated by a microwave plasma. More than a hundred different layers with different refractive indexes (a function of glass composition) may be deposited by either process before the tube is collapsed to form a glass rod. 

A brief review of the literature concerning the several materials employed in the fabrication of both TIR and ARROW structures is given in Table 2. The processes employed are completely different, ranging from molecular beam epitaxy to several chemical vapor deposition (CVD) systems, such as low-pressure CVD (LPCVD) or plasma-enhanced CVD (PECVD). As a rule, all suitable materials for ARROWS (and in general for IOCs) should have homogeneous refractive indexes, high mechanical and chemical stability, few... 

Chemical vapor deposition is not restricted to the microelectronics industry. It is the key process in the fabrication of optical fibers where it enables grading of the refractive index as a function of the radial position in the fiber (JO. In the manufacturing industry the technique provides coatings with special properties such as high hardness, low friction, and high corrosion resistance. Examples of CVD reactions and processes are given in Table 1. 

Armelao et al. (2005) fabricated LaCoOs thin films by the combination of chemical vapor deposition (CVD) and sol-gel methods. Two sequences were adopted to prepare the target film (i) sol-gel of Co-O on CVD La-O (ii) CVD of Co-O on sol-gel La-O. Losurdo et al. (2005) further investigated the spectroscopic properties of these films by ellipsometry in the near-IR and UV range. The former film has a larger crystallite size, a lower refractive index, and a higher extinction coefficient. It also presents a semiconductor-to-metal transition at a temperature of 530 K. Contrarily, the latter film has a smaller crystallite size, a higher refractive index, a lower extinction coefficient and a semiconductor behavior. 

Inorganic BARCs are typically deposited by chemical vapor deposition (CVD) techniques, which affords the possibility of tuning the refractive index n and the extinction coefficient k by adjustments of the film composition and thickness. 

Fig. 5.11. (a) Spin-coated polymer 1 films (40-80 nm thick, with refractive index (n 1.70) are coated on a transparent 200-nm-thick film of chemical vapor deposited parylene (n 1-67), forming a two-layer index-matched waveguide on glass (n 1.45). (b) Spin-coated polymer 1 films (40nm) coated on DFB gratings fabricated from PDMS. (c) Ring-mode laser structure produced by dip-coating polymer 1 on a 25 mm diameter silica optical fiber... 

Vitreous silica has a unique set of properties. It is produced either from natural quartz by fusion or, if extreme purity is required, by chemical vapor deposition or via a sol-gel routes. Depending on the manufacturing process, variable quantities impurities are incorporated in the ppm or ppb range, such as Fe, Mg, Al, Mn, Ti, Ce, OH, Cl, and F. These impurities and radiation-induced defects, as well as complexes of impurities and defects, and also overtones, control the UV and IR transmittance. In the visible part of the spectrum, Rayleigh scattering from thermod)uiamically caused density fluctuations dominates. Defects are also responsible for the damage threshold under radiation load, and for fluorescence. The refractive index n and the absorption... 

Acronyms and variables cold crystalhzation (CC) cobalt molybdenum catalyst (CoMoCAT) chemical vapor deposition (CVD) dichlorobenzene (DCB) high-pressure carbon monoxide (HiPCO) isotactic polypropylene (iPP) melt crystalhzation (MC) melt flow index (MFl) poly( -caprolactone) (PCL) polydispersity index (PDD polyethylene (PE) polyethylene oxide (PEO) poly (ethylene-propylene-diene) [P(E-PP-diene)] poly(ethylene 2,6-naphthalate) (PEN) poly(ethylene terephthalate (PET) poly(L-lactic acid) (PLLA) poly(trimethylene terephthalate (PTMT) poly(vinyl alcohol) (PVA) 1,1,2,2-tetrachloroethane (TCE) tetrahydrofuran (THE) weight-average molecular weight = ] number-average molecular weight Avrami exponent for neat polymer = Avrami exponent for CNT composite = Avrami rate constant for neat polymer = Avrami exponent for composite = neat polymer crystalhzation... 

AC Greenham, BA Nichols, RM Wood, KL Lewis. Optical interference filters with continuous refractive index modulations by microwave plasma-assisted chemical vapor deposition. Opt Eng 32 1018-1024, 1993. 

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