CORRELATING CHEMICAL AND WATER PURITY TO THE SURFACE METAL ON SILICON WAFER DURING WET CLEANING PROCESS

Trace metals in hydrogen peroxide and high-purity water, used in wet cleaning of wafers, is correlated to the metallic contamination of the wafer surface since metal contamination adversely impacts IC device yield. Hydrogen peroxide with different level of trace metals, ranging from 100 ppt level to 10 ppb level, is used in the experiment to determine the level of selected metal deposition on the silicon surface. Significant amounts of these trace metallic impurities can be removed by subsequent treatment of the silicon wafer by an acidified solution of water. Contamination of a wafer surface by sodium is also correlated to the level of sodium present in deionized water used in the final rinsing of the wafer. The threshold and mechanism for metal deposition for various metals on wafer surfaces are different. This information is useful in determining purity requirements for process chemicals and improving the wet cleaning process for the next generation of semiconductor devices.     

Role of organically modified layered silicate as an active interfacial modifier in immiscible polystyrene/polypropylene blends

The role of organically modified layered silicate as a compatibilizer for immiscible polystyrene (PS) with polypropylene (PP) or polypropylene grafted with maleic anhydride (PP-g-MA) blends was investigated. Scanning electron micrographs (SEM) revealed efficient mixing of the polymers in the presence of organically modified layered silicate. X-ray diffraction (XRD) patterns and transmission electron microscopic (TEM) observations showed that silicate layers were either intercalated or exfoliated, depending on their interactions with the polymer pair, and were located at the interface between the two polymers. The compatibilizing action of the organically modified layered silicate resulted in a decrease in interfacial tension and particle size and in a remarkable increase in mechanical properties of the modified immiscible blends.     

A proposed structural model for amyloid fibril elongation: domain swapping forms an interdigitating {beta}-structure polymer

We propose a model illustrating how proteins, which differ intheir overall sequences and structures, can form the propagating,twisted ß-sheet conformations, characteristic of amyloids.Some cases of amyloid formation can be explained through a `domainswapping' event, where the swapped segment is either a ß-hairpinor an unstable conformation which can partially unfold and assumea ß-hairpin structure. As in domain swapping, herethe swapped ß-hairpin is at the edge of the structure,has few (if any) salt bridges and hydrogen bonds connectingit to the remainder of the structure and variable extents ofburied non-polar surface areas. Additionally, in both casesthe swapped piece constitutes a transient `building block' ofthe structure, with a high population time. Whereas in domainswapping the swapped fragment has been shown to be an     

Efficient catalytic epoxidation of olefins with hierarchical mesoporous TS-1 using TBHP as an oxidant

A series of hierarchical mesoporous TS-1 zeolites with MFI structure were successfully synthesized via hydrothermal route using amphiphilic organosilanes as pore directing templates. These materials were characterized by nitrogen sorption (for surface area, pore volume and pore size distribution), FTIR, SEM and UV–Visible spectroscopy. These materials are efficient catalysts for liquid phase epoxidation of olefins using TBHP as the oxidant. All these TS-1 samples oxidized cyclohexene selectively into epoxide. For the TS-1 sample with 4.4 % Ti complete conversion of cyclohexene into epoxide was observed.     

Cover Picture: Macromol. Mater. Eng. 8/2005

Summary: Poly(butylene succinate‐co‐adipate) (PBSA) and organically modified montmorillonite (OMMT) nanocomposites of three different compositions were prepared by melt‐extrusion in a batch mixer. The structure of the nanocomposites was studied using X‐ray diffraction (XRD) and transmission electron microscopy (TEM) that revealed a coexistence of exfoliated and intercalated silicate layers dispersed in the PBSA matrix, regardless of the silicate loading. The degree of crystallinity of PBSA decreases with the addition of OMMT platelets. Dynamic mechanical analysis revealed remarkable increase in flexural storage modulus when compared with that of neat PBSA. Tensile property measurements exhibit substantial increase in stiffness with simultaneous increase in elongation at break of nanocomposites as compared to that of neat PBSA. The effect of clay loading on the melt‐state linear viscoelastic behavior of mixed intercalated/exfoliated nanocomposites was also investigated.

Elongation at break of compression molded annealed samples of neat PBSA and various PBSACNs.     

Formation of BaCrO4 NanoCrystallites within Thermally Evaporated Sodium Bis-2-Ethylhexyl-Sulfosuccinate and Stearic Acid Thin Films

This paper describes the growth of barium chromate (BaCrO₄) nanocrystallites within thermally evaporated thin films of stearic acid (StA) and sodium bis-2-ethylhexyl-sulfosuccinate by a process of Ba²⁺ ion entrapment followed by in situ reaction with CrO₄²⁻ ions. Dense spherical assemblies of BaCrO₄ nanocrystallites of very uniform size (∼50 nm) were obtained within the two different host matrices. The spherical assemblies were composed of smaller (ca. 5–10 nm size) BaCrO₄ crystals indicating that efficient size control over crystal size may be exercised by the matrix. Contact angle measurements of the BaCrO₄–StA and BaCrO₄–sodium bis-2-ethylhexyl-sulfosuccinate films indicated that they were hydrophobic, thus pointing to the possible role of hydrophobic interaction between the StA and sodium bis-2-ethylhexyl-sulfosuccinate monolayer-covered BaCrO₄ crystals in the assembly process.     

Visible Light Photocatalysis on Magnetically Recyclable Fe3O4/Cu2O Nanostructures

Catalysis Letters - Magnetically recyclable visible light photocatalysts for the degradation of critical organic pollutants are an urgent industrial requirement. Nonetheless, one component...     

Identification of 4-Anilinoquin(az)oline as a Cell-Active Protein Kinase Novel 3 (PKN3) Inhibitor Chemotype**

Deep annotation of a library of 4-anilinoquin(az)olines led to the identification of 7-iodo-N-(3,4,5-trimethoxyphenyl)quinolin-4-amine 16 as a potent inhibitor (IC₅₀=14 nM) of Protein Kinase Novel 3 (PKN3) with micromolar activity in cells. Compound 16 is a potential tool compound to study the cell biology of PKN3 and its role in pancreatic and prostate cancer and T-cell acute lymphoblastic leukemia. These 4-anilinoquin(az)olines may also be useful tools to uncover the therapeutic potential of PKN3 inhibition in a broad range of diseases.     

Effect of nano-Al2O3 particles on the corrosion behavior of alkyd based waterborne coatings

A modification in the alkyd based waterborne coatings was studied with the addition of 0.05%, 0.1%, 0.2%, and 0.3% nano-Al₂O₃. Corrosion performance of the nano-composite coatings were evaluated by applying these nanocomposites on mild steel substrate and exposing them to salt spray, humidity, and accelerated weathering. Mechanical properties were studied by subjecting the coating to scratch and abrasion test. The results showed that, with an increase in the concentration of nano-Al₂O₃ there was an improvement in the corrosion resistance, UV resistance, and mechanical properties of the coatings indicating the positive effect of addition of nano-Al₂O₃ particles in the coatings. Further, the transparency of the coating was not altered, maintaining the optical clarity of the coating.     

Electrochemical characterization of a new binary oxide of Mo with Co for O2 evolution in alkaline solution

The α-CoMoO₄ oxide has been obtained by a precipitation method and investigated for the first time for electrocatalysis of the oxygen evolution reaction (oer) in alkaline medium. This method produced the pure crystalline CoMoO4 monoclinic phase with crystallite size ∼46 nm and lattice constants: a = 9.666 Å, b = 8.854 Å, c = 7.755 Å and β = 113.82°. The average particle size (based on area density) and the BET surface area of powders of the oxide were 11.58 μm and 9.4 m² g⁻¹, respectively. Results show that the new oxide is quite active for the oer. Values of the Tafel slope and the reaction order with respect to OH⁻ concentration are observed to be ∼60 mV and ∼1, respectively.