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Nanomaterials Engineering

The recent nanotechnology focuses on the 'mesoscopic' systems ranging from 1nm to 1µm. Their size is medium between that of the microscopic system such as atoms and molecules (0.1nm) and that of macroscopic system found in our life space (> 1cm). The mesoscopic systems often show peculiar properties physically and chemically different both from microscopic and macroscopic systems.

We investigate the interaction of ion beams with solid surfaces, and its application to the structural analysis in the mesoscopic region. Properties of thin films with well-controlled nano-structures and -morphologies are also investigated.

Academic Staff

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Kenji KIMURA

Kenji KIMURAProfessor (Graduate School of Engineering)

Researches

He is interested in development of novel ion beam techniques which are useful in various fields especially in the nanotechnology. For this purpose and also from a fundamental point of view he studies interactions of fast charged particles with solids.

Contacts

Room b4S01, Building C3, Katsura Campus
TEL: +81-75-383-3706
E-mail: kimura@kues

Kaoru NAKAJIMA

Kaoru NAKAJIMAAssociate Professor (Graduate School of Engineering)

Researches

He studies ion-solid interactions from various phenomena during collisions between energetic ions and solid target. He also works on improvement of high-resolution Rutherford backscattering spectroscopy (HRBS) and development of new materials using HRBS.

Contacts

Room b4S02, Building C3, Katsura Campus
TEL: +81-75-383-3707
E-mail: kaoru@kues

Research Topics

Studies on interactions of fast ions with solid surfaces

Ion beams produced by accelerators are utilized in various techniques related to the nanotechnology such as surface analysis, surface modification, synthesis of new materials, ion beam micromachining. Understanding of the interaction of fast ions with solids especially with surfaces is a key issue to develop those techniques.

When fast ions are incident onto a solid surface at a glancing angle, they do not penetrate into the solid but just into the region very close to its surface before being reflected specularly. This phenomenon called specular reflection of fast ions is very suitable to investigate ion-surface interactions.

Figure 1 shows what happens during the specular reflection of fast ions. Backscattering of ions, sputtering of target atoms, charge exchange between ions and surfaces, secondary electron emission, nuclear reactions may occur. Various kinds of ion beam techniques base on these phenomena.

Schematic drawing of the specular reflection of fast ions at a solid surface

Figure 1: Schematic drawing of the specular reflection of fast ions at a solid surface.

Development of high-resolution RBS and downsizing of its system

Atomic-scale analysis technique with higher resolution of sub-nm is needed for progress of nanotechnology.

We have successfully improved depth resolution of Rutherford backscattering spectroscopy (RBS) from 10 nm to 0.2 nm and pioneered layer-by-layer analysis using high-resolution RBS (HRBS). Figure 2 shows a HRBS spectrum of PbSe(111), in which separate peaks corresponding to Pb and Se atoms in the successive atomic layers is observed.

Commercial HRBS system has been developed jointly with Kobe Steel, Ltd. and it is used in various fields such as development of magnetic thin films and ULSI.

We apply HRBS for development of new materials hand-in-hand with companies and universities at home and abroad. Study for further downsizing and improvement of HRBS system is carried on for wider applications of HRBS, for example, application to in-line check at a factory.

HRBS spectrum of PbSe(111)

Figure 2: HRBS spectrum of PbSe(111)

Thin films with tailored nano-morphologies

Unique structures and properties of obliquely deposited thin films have been extensively investigated since the end of the 1950's. Recently, thin films with highly controlled isolated columns such as helix and zigzag have been developed. These ''hypercolumnar'' structures are engineered by dynamic oblique deposition (DOD), in which the deposition angle and/or the azimuthal deposition direction are varied dynamically during the deposition.

The thin films prepared by DOD show the optical, magnetic and mechanical anisotropies, which are related to the shape of columns. In our laboratory, these useful shape-related properties are investigated for the purpose of the application to optical devices, micro-machine and catalyst.

Figure 3 shows the scanning electron micrograph of the thin film of Ta2O5 with hybrid columnar structure prepared by the dynamic oblique deposition. Note that the layers with zigzag, helix and cylindrical columns are stacked without any etching or lithography.

Scanning electron micrograph of the thin film of Ta2O5 with hybrid columnar structure prepared by dynamic oblique deposition

Figure 3: Scanning electron micrograph of the thin film of Ta2O5 with hybrid columnar structure prepared by dynamic oblique deposition.