Fused Silica Materials Research Articles

Non-aqueous capillary electrophoresis with electrochemical detection

The application of electrochemical detection (ED) in conjunction with non-aqueous capillary electrophoresis (CE) is described. Using an acetonitrile-based buffer system only minor effects of the high voltage on the electrochemical detection circuit occur during CE experiments. Thus, for the first time CE–ED measurements are performed employing 75-μm I.D. capillaries without a special capillary modification or interruption. Capillaries from various sources are evaluated regarding their suitability for non-aqueous CE–ED. All fused-silica capillaries tested allow reproducible measurements. However, there are differences in separation efficiency depending on the fused-silica material used. The analytical characteristics of non-aqueous CE–ED are explored using ferrocene and (ferrocenylmethyl)trimethylammonium perchlorate ([FcMTMA]ClO 4) as model analytes. The reproducibility of migration time and signal height is expressed by relative standard deviations of 0.18 and 1%, respectively ( n=10). The limit of detection for [FcMTMA]ClO 4 is 6×10 −8 M. Practical applications concerning the determination of dye compounds such as malachite green, crystal violet and rhodamine B are discussed. A remarkably good stability of electrode response is observed for extended measuring periods owing to the well-defined surface characteristics of the platinum electrode in the acetonitrile-based medium.

KrF-laser irradiation induced defects in all silica optical fibers

High power UV laser irradiation of synthetic fused silica material induces transient absorption bands centered at 215 and 265 nm. The temporal behaviour of the 215 and the 265 nm absorption bands and also of the 248 nm laser transmission were measured with a transient absorption spectrometer during KrF excimer laser irradiation. Fiber samples made from stoichiometric and non-stoichiometric fused silica core material were irradiated at room temperature. The absorption at 215 nm correlates with the laser absorption in stoichiometric materials, whereas in the sample with oxygen rich core material a linear correlation is observed for 265 and 248 nm. The experimental data give evidence that the laser induced decrease in transmission at the laser wavelength can be reduced by using stoichiometric material.

Detection of Hydrogen in Bulk and Thin Film Silicon Dioxide by Hydrogen Nuclear Magnetic Resonance

ABSTRACTHydrogen is a common impurity in silicon dioxide (SiO2) which can influence its optical and electronic properites. Here, nuclear magnetic resonance (NMR) is applied to study of hydrogen in these materials, despite their relatively low hydrogen content. We present results for bulk fused silica as well as thermally grown films of SiO2 on silicon. These experiments demonstrate the potential of solid state NMR for studying low hydrogen content film systems. In bulk fused silica, we have observed that although the majority of hydrogen is isolated, a small number of centers exist involving adjacent silanol pairs. These pairs react during high temperature annealing as well as during deep ultraviolet irradiation. Furthermore, the presence of these centers is related to the susceptibility of fused silica to radiation damage. The results obtained on the fused silica material are compared to SiO2 films on silicon. The NMR spectra and relaxation associated with thick (>1μm) wet SiO2 films are similar to those for the fused silica while the NMR data for thinner oxide more closely resembles those of surface water on silica gel.

Modification of Fused Silica Materials for Excimer Laser Optics—measurement of laser induced defects and its reformation—

ABSTRACTFused silica is widely used material in window and lens applications for excimer laser processing. The transmittance of the laser beam in fused silica is attenuated approximately 40% by high fluence ArF excimer laser irradiation. The attenuation of the transmittance corresponds to the growth of an absorption band at 215nm. This phenomenon is troublesome for laser lithography. To investigate this effect, we examined the laser induced luminescence and absorption under various conditions. The 215nm absorption band was diminished by annealing at 900 °C for 2 hours in He ambient. Ke could successfully obtain good optical material, whose transmittance remains constant with increasing ArF laser(193nm) shot exposure.

Measurement of the complex refractive index and complex dielectric permittivity of T.P.S. space shuttle tile materials at millimeter wavelengths

Complex Refractive Index and Dielectric Permittivity studies of presently used space shuttle tile materials at millimeter wavelength region reveal these tiles to exhibit similar absorption characteristics as fused silica materials. This absorption is mainly related to the water content in the specimen. A strong bire-fringence is observed at least in one of these fibrous refractory composite materials.

Properties of untreated and treated glass capillary surfaces and their contribution to solute-stationary phase interaction and film fixation of the stationary liquid

The properties of support surfaces of glass capillary columns pre-treated by various procedures such as etching, leaching, dealkalization and deactivation (silanization, PSD treatment, “baking”) determine their successful practical application. A comparative study of the dependence of the performance (tailing behaviour, sample capacity, temperature stability) of polar and non-polar column types on the support surface properties was carried out, using fused silica material which does not require extensive surface pre-treatment. Although the coatability of this material is limited, the availability of fused silica is of great value for the chromatography of highly polar solutes, especially at very low column loads such as arise in trace analysis.

Variation of refractive index with wavelength in fused silica optical fibers and preforms

The variation of the refractive index of an unclad fused silica fiber and the preform from which it was pulled was determined over the wavelength range 0.5–1.1 μm, in 0.025-μm steps. The index is determined from an analysis of the backscattered radiation produced when light from an appropriately filtered xenon-arc source impinges transversely upon the fiber or preform. The variation of the index of refraction of the fiber follows those of the preform and published values for bulk fused silica material to within 2 parts in 10−4, with the exception of two points at 0.65 and 0.95 μm.