Microstructure-related properties at 193 nm of MgF2 and GdF3 films deposited by a resistive-heating boat

MgF2 and GdF3 materials, used for a single-layer coating at 193 nm, are deposited by a resistive-heating boat at specific substrate temperatures. Optical characteristics (transmittance, refractive index, extinction coefficient, and optical loss) and microstructures (morphology and crystalline structure) are investigated and discussed. Furthermore, MgF2 is used as a low-index material, and GdF3 is used as a high-index material for multilayer coatings. Reflectance, stress, and the laser-induced damage threshold (LIDT) are studied. It is shown that MgF2 and GdF3 thin films, deposited on the substrate at a temperature of 300 degrees C, obtain good quality thin films with high transmittance and little optical loss at 193 nm. For multilayer coatings, the stress mainly comes from MgF2, and the absorption comes from GdF3. Among those coatings, the sixteen-layer design, sub/(1.4L 0.6H)8/air, shows the largest LIDT.     

Generation of uniaxial tensile strain of over 1% on a Ge substrate for short-channel strained Ge n-type Metal-Insulator-Semiconductor Field-Effect Transistors with SiGe stressors

Tensile strain of over 1% in Ge stripes sandwiched between a pair of SiGe source-drain stressors was demonstrated. The Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET)-like structures were fabricated on a (001)-Ge substrate having SiO₂ dummy-gate stripes with widths down to 26 nm. Recess-regions adjacent to the dummy-gate stripes were formed by an anisotropic wet etching technique. A damage-free and well-controlled anisotropic wet etching process is developed in order to avoid plasma-induced damage during a conventional Reactive-ion Etching process. The SiGe stressors were epitaxially grown on the recesses to simulate strained Ge n-channel Metal-Insulator-Semiconductor Field-Effect Transistors (MISFETs) having high electron mobility. A micro-Raman spectroscopy measurement revealed tensile strain in the narrow Ge regions which became higher for narrower regions. Tensile strain of up to 1.2% was evaluated from the measurement under an assumption of uniaxial strain configuration. These results strongly suggest that higher electron mobility than the upper limit for a Si-MOSFET is obtainable in short-channel strained Ge-nMISFETs with the embedded SiGe stressors.     

Photoelectrochemical reactions of electrodes modified with composites between conjugated polymer or ruthenium complex and single-walled carbon nanotubes

Composite materials between conjugated polymer; poly[2-methoxy-5-(2'-ethylhexyloxy)-1.4-phenylene vinylene] (MEHPPV), or ruthenium(II)-tris(2,2'-bipyridine) (Ru(bpy)₃²⁺)-poly(sodium 4-styrenesulfonate) (PSS) complex and single-walled carbon nanotubes (SWNTs) were fabricated using polymer wrapping method. Formation of SWNT/MEHPPV or SWNT/PSS/Ru(bpy)₃²⁺ composite was confirmed by absorption and fluorescence spectra, and AFM images. Electrode modified with SWNT/MEHPPV or SWNT/PSS/Ru(bpy)₃²⁺ composite was prepared by casting from DMF solution of SWNT/MEHPPV or aqueous solution of SWNT/PSS/Ru(bpy)₃²⁺. The electrode modified with SWNT/MEHPPV or SWNT/PSS/Ru(bpy)₃²⁺ composite showed photocurrent response due to photoexcitation of MEHPPV or Ru(bpy)₃²⁺. The photocurrents are ascribed to photoinduced electron-transfer reaction from excited state of MEHPPV or Ru(bpy)₃²⁺ to SWNT.     

Experimental study on automotive cooling and heating air conditioning system using CO2 as a refrigerant

Recently, as one of the countermeasures against the global warming and energy conservation problems, natural refrigerants such as CO₂ are now paid attention as substitutes for HFCs in automotive air conditioning systems. Also, in recent years because the heat release from the eco-car's engine decreases, there is a problem that the present automotive heating air conditioning system cannot provide sufficient heating capacity.

As an alternative approach, we focused on a solution utilizing a CO₂-based heat pump, whereby the waste heat from the heat pump cycle during dehumidification of the incoming air (referred to as the dehumidifying condition) is recovered and used as an auxiliary heat source instead of an electric heater. Based on this concept, we aimed to develop an effective automotive cooling and heating air conditioning system using CO₂ as a refrigerant.

As the result, a prototype CO₂ automotive cooling and heating air conditioning system for medium-sized cars was successfully developed. With this system, performance superior to that of the present HFC134a system can be achieved.     

Characterization of AlF3 thin films at 193 nm by thermal evaporation

Aluminum fluoride (AlF3) was deposited by a resistive heating boat. To obtain a low optical loss and high laser-induced damage threshold (LIDT) at 193 nm, the films were investigated under different substrate temperatures, deposition rates, and annealing after coating. The optical property (the transmittance, refractive index, extinction coefficient, and optical loss) at 193 nm, microstructure (the cross-sectional morphology, surface roughness, and crystalline structure), mechanical property (stress), and LIDT of AlF3 thin films have been studied. AlF3 thin films deposited at a high substrate temperature and low deposition rate showed a lower optical loss. The highest LIDT occurred at the substrate temperature of 150 degrees C. The LIDT of the films prepared at a deposition rate of 2 A/s was higher than that at other deposition rates. The annealing process did not influence the optical properties too much, but it did increase the LIDT and stress.     

Influence of thermal annealing and ultraviolet light irradiation on LaF3 thin films at 193 nm

Lanthanum fluoride (LaF3) thin films were prepared by resistive heating evaporation and electron-beam gun evaporation under the same deposition rate, deposition substrate temperature, and vacuum pressure. The coated LaF3 films were then treated by heat annealing and UV light irradiation. The optical properties, microstructures, stress, and laser-induced damage threshold (LIDT) at a wavelength of 193 nm were investigated. The surface roughness, optical loss, stress, and LIDT of the films were improved after the annealing. The films had better properties when irradiated by UV light as compared with heat annealing.     

Reverse engineering of spatial patterns in cellular automata

Cellular automata produce spatial patterns when specific rules for time development are given. This paper deals with an inverse problem of identifying the rules for spatial patterns given. Although only rules of one-dimensional elementary cellular automata and one-dimensional probabilistic cellular automata have shown here, the system can deal with two-dimensional one. When the rule identification has not been fully successful due to the lack of information in the spatial pattern, the system is able to give an identifiable part of the rules with a format of Wolfram’s rule number. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

Self-rehealing characteristics of a sodium current limiter and its overcurrent coordination for low-voltage distribution system

The sodium current limiter developed and applied for low voltage use is not a current limiting fuse but a new type of reusable current limiting device that utilizes metallic sodium as a fusible element. Excellent current limiting performance and quick self-rehealing properties of the sodium limiter allowed highly reliable electric power systems to be obtained economically and compactly. Here we examine experimentally the rehealing properties of the sodium limiter after current limiting operation and discuss the overcurrent coordination of the sodium limiter for a low-voltage distribution system. The results are summarized here:

• 1 (1) The resistance of the sodium limiter, being between about one thousand and several thousand times its normal resistance r₀ at room temperature during a current limiting operation of short circuit fault currents, changes abruptly to 30 to 40 times its r_o value just after the disappearance of the fault current and falls steadily to r_o.
• 2 (2) The sodium limiter can recover current-carrying capability for an overload current even immediately after a current limiting operation and maintain its capability for the following normal load current. The upper limit of the recovery of the sodium limiter is given by its overcurrent against the time characteristics under the normal condition.
• 3 (3) The self-rehealing characteristics of the sodium limiter presented here give the ability to design a low-voltage motor control center using the sodium limiter which maintains maximum service continuity up to high fault currents.

     

Preparation of an activated carbon artifact: factors influencing strength when using a thermoplastic polymer as binder

An activated carbon artifact was prepared through mixing, moulding, curing and carbonizing, using polyvinylbutyral resin (PVB) as the binder, dibutyl phthalate (DBP) as a plasticizing agent and isocyanuric acid ester as a cross-linking agent to clarify influential factors on its strength. Preparation conditions such as moulding pressure, temperature and time of curing, carbonization and the amount of cross-linking agent were varied to find their influences on the strength of the resultant form. The form was observed under SEM of wide scope to find correlations between its morphology and strength. The closed packing of the activated carbon filler and the plastic binder was always favorable to develop the strength of the form. The curing extent of PVB, which was influenced by curing atmosphere, temperature and time, and cross-linking agent, was found to govern the strength of the forms. Air or oxygen is very essential for the curing. The optimum temperature was found to be 200°C and longer curing time is beneficial to improve the strength. The cross-linking agent improved the strength of the form up to 7000 kPa through accelerating the cross-linkage of PVB resin. Sufficient curing allows the rapid heating up to 10°C/min for the development of the strength by maintaining the shape of the form. The thermoplastic powders are highly dispersed onto the surface of activated carbons and are cured sufficiently there to adhere the activated carbon grains. Sufficient curing stabilizes the thermoplastic polymer to be thermosetting, anchoring the grains through the carbon bond for higher strength of the carbonized form. PVB resin is cured into heat-resisting cross-linked chains through oxidative condensation onto the activated carbon surface where the oxygen functional groups appear to play important roles in the curing.     

为新发动机新气门可变动作角与升程(VVEL)机构开发的新粉末冶金零件

这2个粉末冶金零件是日产汽车公司藤木章教授等新近研发的用于V6发动机的重要零件。曾荣获日本粉体粉末冶金协会第二次(2009年度)新技术新制品奖,承蒙日本粉体粉末冶金协会准予本刊译为中文刊载,特向日本粉体粉末冶金协会致谢,并向相关业者予以介绍。