Evidence is presented that in dilute aqueous solutions of a Py-PEO-Py polymer (Py = pyrene, PEO = polyethylene oxide)) (Aín = 8000, MJM" = 1.08), 7% of the polymeric molecules exist in an endassociated conformation. When excited by UV light, dilute (less than "6 M) solutions of the polymer exhibit typical pyrene monomer and excimer fluorescence. The excimer fluorescence is shown to arise from intramolecular association only. Part of the excimer emission arises from diffusional approach and endto-end cyclization during the lifetime of the excited pyrene monomer. The observation is that a significant portion of the excimer emission arises from direct UV excitation of polymers that exist in an intramolecularly end-associated conformation. We can make a clear distinction between excimers formed via diffusional end-to-end cyclization and direct excitation of associated end pairs by observing that selective quenching of the excited monomer leads to a decrease of the former type and not the latter. Spectral information, as well as dynamic and static quenching data, is presented to support this hypothesis. A kinetic model is developed, and rate parameters are extracted from data.

To elucidate the fundamentals of chemical mechanical polishing (CMP) of silicon nitride, low pressure chemical vapor deposited silicon nitride is analyzed by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy both before and after CMP, demonstrating the salient increase of oxygen content, amine species, and silanol groups forming on the nitride surface. In addition, chemical testing of the collected slurry identifies ammonia as one of the nitride reaction products during CMP. Nitride hydrolysis is proposed as the dominant chemical reaction, through which the nitride surface is chemically modified and softened, enabling continuous material removal with a process that achieves atomic-scale surface smoothness. Moreover, the nitride polish rate can be promoted or suppressed through the modulation of the nitride hydrolysis.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.6.218.72 Downloaded on 2015-04-05 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.6.218.72 Downloaded on 2015-04-05 to IP

Articles you may be interested inFormation of nickel silicide and germanosilicide layers on Si(001), relaxed Si Ge ∕ Si ( 001 ) , and strained Si/relaxed Si Ge ∕ Si ( 001 ) and effect of postthermal annealingThe formation of NiSi films on Si was studied using Rutherford backscattering spectrometry, atomic force microscopy, and ellipsometry. NiSi is an attractive candidate for use as a gate contact material due to its low metal-like resistivity and large processing window ͑350-750°C͒. Three phases, Ni 2 Si, NiSi, and NiSi 2 , were identified in this temperature range, and their optical databases in the 2-4 eV photon range were established, and used to model real-time ellipsometry data. It is shown that real-time ellipsometry can be used to monitor and follow the formation of the various Ni-Si phases. We have also observed the onset of agglomeration of the silicide for longer time anneals at temperatures of 500-700°C, which is much lower than 1000°C where agglomeration has been reported to occur.

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In this investigation, two kinds of ZrO2 samples were prepared. The ZrO2 films of about 150 Å by PVD were used for physical characterization and the ultrathin ZrO2 films of about 40 Å by RTCVD were used for electrical characterization of MOS capacitors. The samples were annealed in a rapid thermal processing (RTP) system at temperatures of 400–1050 °C in various gas ambients, including O2, N2, forming gas (H2/Ar), wet H2 (15% H2O in H2), and wet O2 (15% H2O in O2). Spectroscopic ellipsometry (SE) with a two layer BEMA optical model was used to characterize the ZrO2 thickness and evaluate the microstructure. A wet etch rate test of ZrO2 films in 1:100 HF solution using SE indicated two distinct etch rates, with a slower initial rate followed by a faster rate. The measured etch rates are dependent of temperature, indicating 4.85 and 38.9 Å/min at 25 and 45 °C, respectively. The RTP annealing temperature and gas ambients have a significant effect on the ZrO2 film etch rate. Rutherford backscattering spectrometry (RBS) and x-ray photoelectron spectroscopy depth profile were used to characterize the films. Three ZrO2 samples were measured by both cross section transmission electron microscopy and SE, indicating that the thickness difference between two techniques is only 1 Å. A mercury probe was used to characterize the electrical properties of the physical vapor deposition dielectric films. The electrical characterization of ultrathin ZrO2 films show that the gas ambients in postdeposition anneal affect the equivalent oxide thickness (EOT) and leakage current significantly. The lowest EOT achieved in this study is 10.9 Å for the sample spike annealed in N2. The RTP effect on electrical properties of ultrathin ZrO2 was also discussed.

The electron cyclotron resonance plasma oxidation of silicon was investigated using in situ static spectroscopic ellipsometry during process and dynamic real time ellipsometry at oxidation temperatures between 80 and 400 °C and at various applied bias’. Successful optical modeling of the ellipsometric data was accomplished using a two layer model, in which the top layer is a pure silicon dioxide film over an interface layer. The kinetics results are compatible with the Cabrera–Mott theory for the oxidation by charged species in the limit of low electric field. The effect of applied bias suggests that the oxidizing species is O−. The energy activation is 0.18 eV, substantially lower than the thermal oxidation value.

The robust design of horizontal axis wind turbines, including both parameter design and tolerance design, is presented. A simple way of designing robust horizontal axis wind turbine systems under realistic conditions is outlined with multiple design parameters (variables), multiple objectives, and multiple constraints simultaneously by using the traditional Taguchi method and its extensions. The performance of the turbines is predicted using the axial momentum theory and the blade element momentum theory. In the parameter design stage, the energy output of the turbine is maximized using the Taguchi method and an extended penalty-based Taguchi method is proposed to solve constrained parameter design problems. The results of the unconstrained and constrained parameter design problems, in terms of the objective function and constraints are compared. Using an appropriate set of tolerance settings of the parameters, the tolerance design problem is formulated so as to yield an economical design, while ensuring a minimal variability in the performance of the wind turbine. The resulting multi-objective tolerance design problem is solved using the traditional Taguchi method. The present work provides a simple and economical approach for the robust optimal design of horizontal axis wind turbines.