This article reports the use of ac-field-induced charges at the corners of microstructures on fiber-optic sensing chips to generate electro-osmotic vortex flows in flow cell channels that can accelerate solute binding on the fiber. The sensing chip made of a cyclic olefin copolymer COC substrate contained a flow cell channel of dimensions 15 mm x 1 mm x 1 mm. A partially unclad optical fiber was placed within the channel. Relief-like strip structures of 25-mum thickness fabricated on the channel bottom were produced with an injection-molding process. The external electric field lines penetrating through the corners of the plastic microstructures induce charges on the corner surfaces to build up electrical double layers. When a high-frequency ac field (approximately 100 kHz) is used to flip the field polarities quickly, neutralization of the induced charge cannot be accomplished. The electrical double layer is therefore sustained. When absorbed charges in the double layer are driven by the external field, electro-osmotic flows are generated. The unclad portion of the fiber was coated with biotin-functionalized gold nanoparticles. The streptavidin solution was filled in the channel from the feeding tube, and the ac field (approximately 50 V/cm) was subsequently turned on for 30 s. The ac-field-induced electro-osmotic flows can accelerate solute transport in the sensing channel to enhance the binding kinetics of streptavidin molecules with biotin probes implanted on the gold nanoparticle surface. As a result, the fiber-optic localized plasmon resonance (FO-LPR) sensing signal becomes steady as soon as the external field is turned off. In contrast, the signal cannot reach steady state until 200-300 s in a typical static sensing cell. A significant reduction in the sensing response time is demonstrated. The binding assay of streptavidin with immobilized biotin on gold nanoparticle-coated sensing fibers was validated using this mixing device. The detection limit for streptavidin of approximately 10(-11) M is close to the reported values obtained using static cells. Similarly, the sensing response time of an orchid Odontoglossum ringspot virus (ORSV) sample was reduced from 1000 to 330 s when an external field was applied to mix the fluid for 60 s, even though the detection limit was maintained.

Multiwavelength, high resolution micro-Raman spectroscopy was applied to in-line process monitoring and diagnostics of undoped and B-doped Si1-xGex epitaxy on Si(100) device wafers. This noncontact technique was used to monitor the Ge content, B concentration and thickness of single and double Si1-xGex epitaxial layers. Epitaxial process problems were diagnosed nondestructively. Raman peak positions and full-width-at-half-maximum of the Si-Si peak(s) from the Si1-xGex epitaxial layer(s) and Si substrates, in the wavenumber range of 475 ∼ 535 cm-1, were monitored under ultraviolet and visible excitation wavelengths. The Ge content, B concentration and Si1-xGex epitaxial film structures were verified by secondary ion mass spectroscopy (SIMS) depth profiling results. In-line monitoring of Si-Si and Si Raman peaks is very effective in noncontact material property characterization, epitaxial process optimization, and quality control applications

Non-contact monitoring of Ge content and B concentration in single and double Si1-xGex epitaxial layers on Si(100) device wafers was attempted using high-resolution, multiwavelength micro-Raman spectroscopy. The Ge content and B concentration determined by secondary ion mass spectroscopy (SIMS) depth profiling showed very strong correlation with the position and full-width-at-half-maximum of the Si-Si peak from the Si1-xGex epitaxial layers as determined by Raman measurements. High resolution X-ray diffraction (HRXRD) characterization was done for all wafers to determine Ge and B sensitivity and form comparisons with Raman and SIMS analysis. The non-destructive, in-line monitoring of Ge content and B concentration of single and double Si1-xGex epitaxial layers with thickness ranging from 5 ∼ 120 nm, on small area monitoring pads, was successfully demonstrated by multiwavelength micro-Raman spectroscopy during epitaxial process optimization, material property verification, and quality control applications

B-doped, thin Si1-xGex bi-layers with different Ge content and B concentrations were epitaxially grown on Si(100) device wafers. Diffusion behavior of Ge and B atoms during rapid thermal annealing were monitored by multiwavelength micro-Raman spectroscopy. Raman spectra indicating possible Ge and B redistribution by thermal diffusion was observed from B-doped, thin Si1-xGex bi-layers on Si(100) wafers after rapid thermal annealing at 950°C or higher. Significant Ge and B diffusion in Si1-xGex bi-layers and Si substrates was verified by secondary ion mass spectroscopy. Pile up of B atoms at the surface and at the boundary between Si1-xGex bi-layers was observed in the early stages of thermal diffusion

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