Electrical characterization of high-k gate dielectrics fabricated using plasma oxidation and post-deposition annealing of a Hf/SiO2/Si structure

High permittivity (high-k) gate dielectrics were fabricated using the plasma oxidation of Hf metal/SiO₂/Si followed by the post-deposition annealing (PDA), which induced a solid-phase reaction between HfO_x and SiO₂. The oxidation time and PDA temperature affected the equivalent oxide thickness (EOT) and the leakage current density of the high-k dielectric films. The interfacial structure of the high-k dielectric film/Si was transformed from HfO_x/SiO₂/Si to HfSi_xO_y/Si after the PDA, which led to a reduction in EOT to 1.15 nm due to a decrease in the thickness of SiO₂. These high-k dielectric film structures were investigated by X-ray photoelectron spectroscopy. The leakage current density of high-k dielectric film was approximately four orders of magnitude lower than that of SiO₂.     

An application of bootstrap method for analysis of particle size distribution

The Bootstrap method, which is used widely in statistics, is a very powerful method that can be applied to the analysis of particle size distribution. For a number based measurement, this method can estimate the statistic uncertainty or confidence interval for any statistical quantities of interest from the distribution, with very simple protocol and without any parametric assumptions. This paper gives a demonstration to introduce the method to the community of particle size analysis.     

Edge and Depth from Focus

This paper proposes a novel method to obtain the reliable edge and depth information by integrating a set of multi-focus images, i.e., a sequence of images taken by systematically varying a camera parameter focus. In previous work on depth measurement using focusing or defocusing, the accuracy depends upon the size and location of local windows where the amount of blur is measured. In contrast, no windowing is needed in our method; the blur is evaluated from the intensity change along corresponding pixels in the multi-focus images. Such a blur analysis enables us not only to detect the edge points without using spatial differentiation but also to estimate the depth with high accuracy. In addition, the analysis result is stable because the proposed method involves integral computations such as summation and least-square model fitting. This paper first discusses the fundamental properties of multi-focus images based on a step edge model. Then, two algorithms are presented: edge detection using an accumulated defocus image which represents the spatial distribution of blur, and depth estimation using a spatio-focal image which represents the intensity distribution along focus axis. The experimental results demonstrate that the highly precise measurement has been achieved: 0.5 pixel position fluctuation in edge detection and 0.2% error at 2.4 m in depth estimation.     

Charge transfer between a polymer particle and a metal plate due toimpact

To elucidate the mechanism of contact-impact electrification of insulating particles, the authors measured the charge generated by collision of a single polymer particle onto a metal plate. It was not exclusively the normal component of the impact velocity that determined the amount of impact charging. In order to investigate this great contribution of the impact angle to the impact charging, impact stresses, contact times, and contact areas were measured, and the impact-contact process was discussed. Based on the idea that the “apparent contact area” is supported by some “real contact points” and that the number of these real contact points increases with the particle slipping, a new model called “effective contact area model” was proposed     

Formation of microcapsules of medicines by the rapid expansion of a supercritical solution with a nonsolvent

The rapid expansion from a supercritical solution with a nonsolvent (RESS‐N) was applied to the formation of polymeric microcapsules containing medicines such as p‐acetamidophenol, acetylsalicylic acid, 1,3‐dimethylxanthine, flavone, and 3‐hydroxyflavone. A suspension of medicine in carbon dioxide (CO₂) containing a cosolvent and dissolved polymer was sprayed through a nozzle to atmospheric pressure. The pre‐expansion pressure was 10–25 MPa, and the temperature was 308–333 K. The polymers were poly(L ‐lactic acid) (molecular weight = 5000), poly(ethylene glycol) (PEG; PEG4000, molecular weight = 3000; PEG6000, molecular weight = 7500; and PEG20000, molecular weight = 20,000), poly(methyl methacrylate) (molecular weight = 15,000), ethyl cellulose (molecular weight = 5000), and PEG–poly(propylene glycol)–PEG triblock copolymer (molecular weight = 13,000). The solubilities of the polymers as coating materials and these medicines as core substance were very low in CO₂. However, the solubilities of these polymers in CO₂ significantly increased with the addition of low molecular weight alcohols as cosolvents. After RESS‐N, polymeric microcapsules were formed according to the precipitation of the polymer caused by a decrease in the solvent power of CO₂. This method offered three advantages: (1) enough of the coating polymers, which were insoluble in pure CO₂, dissolved; (2) the microparticles of the medicine were encapsulated without adhesion between the particles because a nonsolvent was used as a cosolvent and the cosolvent remaining in the mixture was removed by the gasification of CO₂; and (3) the polymer‐coating thickness was controlled with changes in the feed composition of the polymer for drug delivery. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 742–752, 2003     

Substitution of Sodium and Silicon in Tricalcium Aluminate

Four types of tricalcium aluminate solid solutions with different concentrations of Na₂O and SiO₂ were prepared and examined using an electron probe microanalyzer. The atomic ratios, including those determined in a previous study, were derived from the oxide compositions and provided excellent correlations between Ca and Na + Si (i.e., Ca = 3.003 − 0.48[Na + Si]), and Al and Si (Al = 1.997 − 1.02Si). Because the replacement reactions, Ca²⁺↔ 2Na⁺ and Ca²⁺+ 2Al³⁺↔ 2Si⁴⁺, independently occur within the same crystal, these reactions have been simply combined together to generate a new formula, Na_{2 x} Ca_{3− x − y} (Al_{1− y} Si _y )₂O₆, where x is the amount of Ca substituted by Na, and y is the amount of Al substituted by Si. This formula leads to the equations Ca = 3 − 0.5[Na + Si] and Al = 2 − Si, which nicely account for the constrained chemical variation of the actual solid solutions with 0 ≤ x < 0.049 and 0 ≤ y < 0.073.     

Thermal properties of hexadecane encapsulated in poly(divinylbenzene) particles

The thermal properties of n‐hexadecane (HD) encapsulated in crosslinked capsule particles containing a water and/or air domain were studied from the viewpoint of heat‐storage applications. The capsule particles were prepared by the microsuspension polymerization of divinylbenzene at 70°C with the self‐assembling of phase‐separated polymer method that we developed. In the differential scanning calorimetric thermograms, pure HD had a single solidification temperature (T_s) peak at 15°C, whereas the encapsulated HD containing a water domain had two peaks at 6 and 1°C. That is, the encapsulated HD containing the water domain required a longer time and lower temperature to complete the solidification than pure HD, which was negative for heat‐storage applications. However, once the particles were dried and the water domain was replaced with air, the problem with the partially lowered T_s improved. The air domain was also found in the encapsulated HD core after solidification because of the shrinkage of HD. The presence of the air domain did not affect the thermal stability of the encapsulated HD. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Study on flame dynamics with secondary fuel injection control by large eddy simulation

In this study, flame dynamics of secondary fuel injection control is investigated by large eddy simulation (LES) in a lean premixed combustor to elucidate the experimental two-stage oscillation suppression phenomenon. Without secondary fuel injection, large-amplitude longitudinal oscillations were observed in the experiment. With constant injection of secondary fuel, the oscillation amplitude was reduced and with harmonic feedback injection, it was further reduced. In this process, the flame shape and the dynamic behavior of the flame were changed. To fill the gap of the experimental data and to understand the flame dynamics, large eddy simulations are carried out. The LES results show that the oscillation reduction is attributable to the roles of both the main flame and the secondary flame. The interaction of the main flame and the vortices is reduced when the injection is on; namely, heat fluctuation is reduced. The secondary flame helps the flame base stabilization and directly modulates the heat release in the feedback injection. The phase relations between the pressure, secondary heat release, and injection velocity are also shown. With these effects from the main and secondary flames combined, the oscillations are suppressed by secondary fuel injection. The present study indicates that LES can be a tool to understand flame dynamics with control.