SiO2 layer

Figure 14. Reflectance of a 100 nm thick silver coating enhanced with two quarter-wave Sio2 layers.

Figure 15.24 shows the fabrication process of the optical filter on a fluorinated polyimide substrate. First, the low-thermal-expansion-coefficient PMDA/TFDB poly(amic acid) solution was spin-coated onto a Si substrate and baked. Then alternate TiO2 and SiO2 layers were formed on the polyimide film by ion-assisted deposition. The multilayered polyimide film was diced and peeled off from the Si substrate. In this way, thin optical filters on a fluorinated polyimide substrate are easily fabricated. 

Er-doped SiO2 layers composed of nc-Si formed by co-sputtering [7], plasma-enhanced chemical vapor deposition [8], or by ion implantation [9,10] exhibit the Er3+ PL at room temperature. The Er3+ excitation in nc-Si/SiO2 structure was found to be caused by the energy transfer from the excitons... 

Tellurium is a narrow band gap semiconductor and is a component of different important binary and ternary semiconductors such as CdTe, PbTe, Cdi.xHgxTe, Pbi.xSnxTe, etc. Heterostructures based on these semiconductors and Si are used for IR detectors, laser diodes, etc. However, little attention has been paid to the features of individual components deposition in electrochemical studies with tellurides. The aim of this work was to investigate cathodic nucleation of Te nanoparticles on n-Si. We also used nanoporous SiO2 layer on Si as a template for Te nanoparticles deposition. Nanopores in SiO2/Si are of particular interest for silicon-based electronics and nanoelectronics [1]. 

Figure 1. Selective growth of semiconductor quantum dots (Ge or Si) in Si windows in an SiO2 layer. In large area Si windows ((bi), (b2), d > 270 nm), few dots per window are grown [4]. In small area windows ((ci), (c2), d < 270 nm) only one dot per window is grown [4], For samples (bi), (b2) the windows in SiO2 were defined by electron beam lithography [4], while for samples (ci), (c2) by focussed ion beam milling [6],...

Si wafers of n-type and (100) orientation covered by thermally grown 100 nm SiO2 layer fabricated at 1100 °C in dry O2, were used as substrates. The wafers were loaded into an oil free evaporation chamber (Varian VT-460), and the system was evacuated down to lxlO 8 Torr. Ge ingot of 99.999 % purity was supported on a molybdenum plate, and it was evaporated using an electron gun, at an evaporation rate of 0.01-0.03 nm/s, at a pressure of lxlO"7 Torr. During evaporation, and for an additional 1 min after this process, the substrate temperature was kept at 350 °C. The temperatures were monitored by small-heat-capacity Ni-NiCr thermocouples, while the film thicknesses were measured by a vibrating quartz probe. For this study, four different samples have been prepared with different Ge evaporation times of 25, 50, 75, and 100 s for samples No. 1, 2, 3, and 4, respectively. After germanium evaporation, the samples were moved to a cold place inside the vacuum chamber. 

Figure 2.31. Calculated p-polarized IRRAS spectra of SIO2 layer of thickness (1)1, (2) 5, (3) 20, and (4) 100 nm located at Ge-AI Interface. Spectra were obtained for values of (a) 30°, (fa) 60°, and (c) 85°. Optical constants of SIO2 were specified In Ref. [2] and of Al in Ref. [75, nee = 4.0.

Mercury iodide offers an example of a layer structure consisting of tetrahedra sharing all of their vertices (Fig. 16.23). Much more frequent are framework structures they include the different modifications of SiO2 and the aluminosilicates that are discussed in Section 12.5. Another important class of aluminosilicates are the zeolites. They occur as minerals, but are also produced industrially. They have structures consisting of certain polyhedra that are linked in such a way that hollows and channels of different sizes and shapes are present. 

Figure 9.30 AFM images of polyethylene films formed on the planar Cr0,/SiO2/Si( 100) model catalyst. The small white stripes are lamellar crystals. These form the well-known spherulite superstructure upon crystallization from the melt. Depending on the layer thickness, spherulite growth stops at different stages of development (adapted from Thiine et at. [901).

The molar ratios in the precursor solution were 100 SiO2 10 Na2O 10 (TPA)20 1600 H2O while hydrothermal treatment was conducted at 130°C for 48 h, followed by an additional treatment at 200°C for 16 h. After washing, drying and calcination at 600°C a zeolite membrane with good gas separation properties resulted. No further characteristics of the layer were given. 

Good adhesion to metals. Avatrel exhibits good adhesion (passes the cross-hatched tape test, ASTM D-3359-95a and IPG 650-TM) to metals such as Cu, Au, Al, Cr, Ti, and Si, as well as SiO2. Polyimides on the other hand require tie layers and adhesion promoters. 

The molten sodium sulphate/sodium silicate system of composition Na2SO4 Na2O-SiO2 has one liquid phase at 1475 K, but as the proportion of silica increases, the melt separates into two layers (, 2). The change from the miscible to immiscible phase of the system has been explained by alterations in the silicate structure as the ratio of Na20 to Si02 decreases. In more basic, less viscous melts, the silicate ions exist in the form of SiO "... 

To a solution of the P-hydroxy-/V-methyl-O-methylamide (0.272 g, 1.55 mol) in tetrahydrofuran (THF) (30 mL) were added carbon disulfide (6.75 mL, 112 mmol) and iodomethane (6.70 mL, 108 mmol) at 0 °C. The mixture was stirred at this temperature for 0.25 h, and then sodium hydride (60% suspension in mineral, 136.3 mg, 3.4 mmol) was added. After 20 min at 0 °C, the reaction was quenched by slow addition to 60 g of crushed ice. (Caution hydrogen gas evolution ). The mixture was raised to room temperature and separated, and the aqueous layer was extracted with CH2CI2 (4x15 mL). The combined organic extracts were dried (Na2SO4), concentrated in vacuo, and purified (SiO2, 5% EtOAc in hexanes) to afford 0.354 g (86%) of the xanthate. To a solution of the xanthatc (2.95 g, 11.1 mmol) in toluene (100 mL) was added tributyltin hydride (15.2 mL, 56.6 mmol) and 2,2 -azobisisobutyronitrilc (AIBN, 0.109 g, 0.664 mmol). The reaction mixture was then heated to reflux for 1 h. The mixture was cooled, concentrated in vacuo, and purified (SiO2, 100% hexanes to remove tin byproducts, followed by 10% EtOAc in hexanes to elute product) to afford 1.69 g (96%) of the/V-methyl-O-methylamide. 

A solution of this ester (8.35 g, 21.6 mmol, 1.0 equivalents) in tetrahydrofuran (THF 100 mL) was cooled to 0 °C, and pyridinium p-toluenesulfonate (PPTS, 500 mg, 2.00 mmol, 0.1 equivalents) and then 2,2-dimethoxypropane (20.0 mL, 163 mmol, 5.9 equivalents) were added. The cold bath was removed and the mixture was stirred at room temperature for 48 h, quenched with saturated aqueous NaHCOs solution, and extracted with EtOAc. The combined organic layers were washed with brine, dried (Na2SO4), filtered, and concentrated. Purification by chromatography on SiO2 (3% ethyl acetate and 1% triethylamine in hexanes, and then 100% EtOAc) afforded the acetonide and a small amount of starting diol which was re-subjected and purified as above. The two batches were combined to afford naphthalene-2-carboxylic acid 2-[(4S)-2,2- dimethyl-[l,3]dioxan-4-yl]-2-methylpropyl ester (9.140 g, 97%) as a clear colorless syrup. Reference Wipf, P Graham, T. H.,/. Am. Chem. Soc. 2004,126, 15346-15347. 

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