Research theme

Development and application of metal ultrafine/nanoparticle fabrication technique

Participated in by

Department of Molecular Engineering, Graduate School of Engineering, Kyoto University; Fukuda Metal Foil & Powder Co., Ltd.; Hitachi Chemical Co., Ltd.

Goal/Milestone

Background to and Position of the Research
This study commenced in 2004 under a group theme of “Development of Metal Foil/Particle Refinement Technology and Large-Capacity Recording Medium.” Morphologic transformation of metal nanoisland films to spherical metal nanoparticles is induced by a pulse laser with a low energy density of 1 J/cm2 or less. Based on this principle, this study aimed to develop a large-capacity recording medium suitable for hologram recording. At the same time, being interested in the applicability of the principle to the production of novel ultrafine metal particles or nanoparticles through top-down-like refinement of various types of metal powder, we have promoted technical development as joint research with Fukuda Metal Foil & Powder. Metal nanoparticles are viewed as a nanotechnology material of the highest practicality, and are under intense study in Japan and abroad in order to develop an efficient production method and find new applications. This technology is attracting a great deal of attention throughout the world. With this background, achievements gained after the initial two to three years of the study drew attention from many sectors due to newspaper coverage. In the latter half of fiscal year 2006, Hitachi Chemical provided cooperation, and in this final fiscal year Hitachi Chemical took part in the project as a participant company. This resulted in improved effectiveness of the research and development program. In addition, the position of this study and its goal setting for commercialization became specific and definite, bringing about a result appropriate for the final fiscal year.

The main pillar of this study is the development of a metal ultrafine/nanoparticle fabrication technique. The basis of this technique is the use of a local nonequilibrium reaction field induced by pulse laser irradiation on metal or metallic compound particles dispersed in a liquid. There are some metal ultrafine/nanoparticles that are difficult or impossible to regulate through the traditional production process although production and supply of them are desired. The purpose of the development is the efficient production of such metal ultrafine/nanoparticles and the establishment (as a business) of a market supply system. Furthermore, participant companies take the initiative in discovering unique applications (the exit) of metal ultrafine/nanoparticles produced by this technique. On the university side, we make use of the suitable environment for fundamental research. More specifically, in parallel with the aforementioned study, we are undertaking the development of optical/photochemical devices and processes designed to substantially enhance faint light absorption or emission. At the initial stage of the research this was a subtheme, but has since developed into a study of applying metal ultrafine/nanoparticles to future plasmonic devices.

Development of Nonvolatile Organic Memory Device
Home information appliances and mobile equipment need to be compact, lightweight, with low power consumption, and environmentally friendly. For memory devices for these applications and business fields of rewritable disposable memory such as IC cards and logistic identification tags, organic memory can be widely applied taking advantages of organic materials, such as lightweightness, material diversity, simple processing, low cost, and low environmental load. In this study, use of organic memory as nonvolatile memory is explored using dielectric hysteresis in organic ferroelectrics. For ferroelectric molecules, vinyliden fluoride oligomer is selected and formed into a crossbar structure to undergo pulse writing and reading tests. While Intel Corporation of the United States conducts organic memory studies using ferroelectric polymers, we believed that the use of an oligomer material would be beneficial to obtain ferroelectric property efficiently and control device’ characteristic variation occurring on device surfaces. Research topics included nanostructure-controlled formation of ferroelectric molecular films, ferroelectric properties, memory durability, and ease of processing. Experiments were conducted according to these topics. The goal of the study was to develop a prototype memory device on a flexible substrate (flexibility is a feature of organic memory) and multilayer memory taking advantage of low-temperature, simple processing.

Electronics
- Electronic conductor-printing ink
- Industrial catalysts
- Environmental catalysts
- Medical/Hygienic materials
- Battery/Capacitor materials
- Painting/Color materials

Medical/Bio engineering
- Biosensors
- Solar cells
- Flexible surface emitting laser
- EL light-emitting devices

Stepwise Milestone Setting
FY 2004
- Clarification of correlations between the form of raw material particles or various laser irradiation conditions and the behavior/efficiency of laser-induced refinement of flakes of various pure metals dispersed in liquid; examination of commercialization feasibility
- Demonstration of physicochemical stability, recording density, and record reproduction capacity of metal nanoisland films as high-density recording medium; determination of optimum materials; development of related elementary technology

FY 2005
- Production feasibility study of ultrafine/nanoparticles of alloys (silver/copper, copper/molybdenum, silver/nickel, etc.); material technology development for volume production; optimization of laser irradiation conditions
- Improvement of performance (sensitivity, resolution, and diffraction efficiency) of hologram recording devices incorporating platinum nanoisland films as principal recording medium; development of multiplexed/multiple recording layer technology

FY 2006
- Upgrading of the test production line using a large (50 W power class) laser; achievement of metal ultrafine/nanoparticle production of approximately 10 g/h per system through composition improvement/extension of metal particle material; solution to peripheral problems associated with upsizing
- Development of a novel plasmonic device using surface plasmon excitation of metal ultrafine/nanoparticles

FY 2007
- Establishment of an engineering system for volume production of high-concentration (several tens of wt%) copper nanoparticle dispersion liquid free of organic protectant
- Development of peripheral techniques for conductor-printing using the aforementioned dispersion liquid; expansion of application range
- Performance improvement of plasmonics-applied enhanced light absorption/emitting device; commercialization tests