Application of polyimide Langmuir-Blodgett films to deep UV resists

The preparation of Langmuir-Blodgett (LB) films based on a photosensitive polyimide precursor 2 and their application to deep UV resists have been studied. LB films fabricated from a mixed monolayer of polyimide precursor 2-octadecyl alcohol-benzoin ethylether (molar ratio, 3:3:1) were found to act as negative working resists with a resolution of 0.5 μm space and 1.0 μm line, a sensitivity of 100 mJ cm^-2 and good plasma etching resistance. They are promising for application as KrF and ArF excimer laser resists corresponding to 16 and 64 Mbit dynamic random access memories.     

Defects generation by hydrogen passivation of polycrystalline silicon thin films

Hydrogen passivation technique is essential for improving the properties of polycrystalline silicon thin films. Elastic Recoil Detection Analysis (ERDA) indicated depth profiles of hydrogen concentration in poly-Si after hydrogen passivation. We have observed that plasma hydrogenation with duration up to 30 min effectively passivated the defects and improved photoluminescence intensity. Over 60 min of hydrogenation, PL intensity started to decrease. Raman scattering spectroscopy and X-ray rocking curve indicated that hydrogen created new defects and/or disorder with an increase in the hydrogen passivation time. Over 60 min, hydrogen started to form Si–H₂ bonding and hydrogen molecules (H₂), which lead to degradation of PL intensity. These peak positions were largely influenced by the grain size.These formations must be formed in quasi-stable sites, which are located at close to grain boundaries. Thus hydrogenation treatment may lead to defect passivation and new defects and/or disorder creation.     

Pt-TiO2 thin films on glass substrates as efficient photocatalysts

Photocatalytic Pt-TiO₂ thin films of various thicknesses (ca. 20 to 100 nm) were prepared on Vycor glass substrates by spray-coating. The photocatalytic activity of the films was examined through the dehydrogenation of methanol in aqueous solution. The plot of the activity against the thickness of the film gave a sigmoidal curve. A drastic increase in activity was observed at about 50 nm thickness. From thin-film X-ray diffraction measurements of the films it was revealed that anatase was formed at a thickness of more than 50 nm, whereas amorphous TiO₂ was formed at thicknesses of less than 50 nm. The increase of activity was, therefore, attributed to the formation of anatase. Compared with powder catalysts, the thin films showed a remarkable improvement in specific photocatalytic activity due to the high dispersion of the catalyst.     

A new vertical IGBT structure with a monolithic over-current,over-voltage, and over-temperature sensing and protecting circuit

A new 600 V vertical Insulated Gate Bipolar Transistor (IGBT) structure with monolithically integrated over-current, over-voltage, and over-temperature sensing and protecting functions has been developed to exploit an extremely excellent trade-off characteristic between an on-state voltage drop and turn-off time for the first time. This device can be easily made by the conventional IGBT fabrication process. An accurate and a real-time device temperature detection, as well as a high withstand capability against over-current and over-voltage conditions (short circuit immunity of 30 μsec, clamped collector voltage of 640 V), have been achieved. Furthermore, an excellent trade-off characteristic of 1.40 V as an on-state voltage drop and of 0.18 μsec as a fall time is also obtained     

Study on LD-VHDL conversion for FPGA-based PLC implementation

In this paper, we propose a flow shop scheduling problem with no-wait flexible lot streaming. The problem involves the splitting of order quantities of different products into sublots and considers alternative machines with different processing times. Sublots of a particular product are not allowed to intermingle; that is, sublots of different products must be non-preemptive. The objective of the problem is the minimization of the makespan. An adaptive genetic algorithm (GA) is proposed, which is composed of three main steps. The first step is a position-based crossover of products and local-search-based mutation for better offspring. The second step is an iterative hill-climbing algorithm to improve the current generation. The last step is the adaptive regulation of the crossover and mutation rates. Experimental results are presented for various sizes of problems to describe the performance of the proposed algorithm and they show promising outcome compared to traditional GAs.     

Crack formation,exfoliation, and ridge formation in 500 °C annealed sol–gel silica coatings on stainless steel SUS304: Part I. Microscopic observations and elemental analyses

Uniformly compact silica coatings of thicknesses >400 nm on Cr- and Ni-containing steels are practically desirable but difficult to obtain. A non-aqueous sol–gel silica coating on SUS304 was studied. After the coated substrates were treated at 500 °C in air, coatings with thicknesses of ～350 to ～1000 nm were obtained that were largely uniform, non-porous, adherent, and with minimal residual organic content, although some cracks and exfoliated sites existed. TEM/EDX analysis indicated that three interlayers were observed between silica and SUS. The innermost one was ～5 nm thick, Cr-rich, highly O-deficient, and formed a tenacious bond between SUS304 and silica; the two others were rather diffuse. The web-like development of ridges resulting from the oxidation of metallic elements (mostly Fe) diffused into the silica through nanoscale defects within the innermost interlayer was also observed. Many of the nanoscale defects seem to be related to SUS grain boundaries. Ni was almost absent in silica coating except in the innermost interlayer and ridges. The mechanisms responsible for these observed properties and phenomena are discussed.     

Solution structure of thermostable cytochrome c-552 from Hydrogenobacter thermophilus determined by 1H-NMR spectroscopy

The solution structure of a thermostable cytochrome c-552 from a thermophilic hydrogen oxidizing bacterium Hydrogenobacter thermophilus was determined by proton nuclear magnetic resonance spectroscopy. Twenty structures were calculated by the X-PLOR program on the basis of 902 interproton distances, 21 hydrogen bonds, and 13 torsion angle constraints. The pairwise average root-mean-square deviation for the main chain heavy atoms was 0.91 +/- 0.11 A. The main chain folding of the cytochrome c-552 was almost the same as that of Pseudomonas aeruginosa cytochrome c-551 that has 59% sequence identity to the cytochrome c-552 but is less thermostable. We found several differences in local structures between the cytochromes c-552 and c-551. In the cytochrome c-552, aromatic-amino interactions were uniquely formed between Arg 35 and Tyr 32 and/or Tyr 41, the latter also having hydrophobic contacts with the side chains of Tyr 32, Ala 38, and Leu 42. Small hydrophobic cores were more tightly packed in the cytochrome c-552 because of the occupancies of Ala 5, Met 11, and Ile 76, each substituted by Phe 7, Val 13, and Val 78, respectively, in the cytochrome c-551. Some of these structural differences may contribute to the higher thermostability of the cytochrome c-552.     

Inhibition of adrenaline-induced lipolysis by ginseng polypeptide and its modified peptides

The anti-lipolysis by ginseng polypeptide and its modified peptides was examined using porcine adipose cells. Ginseng polypeptides modified by amino acid substitution or proteolyzation reduced or lost the inhibiting activity of adrenalin-induced lipolysis. Correlation between the anti-lipolytic activity of ginseng polypeptide and its Mg(2+)- and ribose-binding activities is discussed.