Nano-Process Engineering

Development and application of material processing techniques using nano-sized particle (cluster) ions

Clusters, or aggregates of atoms or molecules, are nano-sized superfine particles that play a role in connecting the macroscopic world around us with the microscopic world of atomic and molecular activity, and which exhibit completely different characteristics to matter in the bulk state. In addition, if clusters are ionized and accelerated, and irradiated on a material surface, they exhibit irradiation effects that are unique to cluster ions, such as the high-density irradiation effect and the multiple collision effect. We are conducting research on forming nano-sized particles having these kinds of properties, from materials that are solids, liquids, or gases at room temperatures, and on the production and engineering applications of cluster ions that can be tailored by controlling not only particle size and structure, but also physical and chemical properties. This research is becoming increasingly important at the forefront of cluster science and materials science, and for the development of leading-edge ion beam process techniques.

Academic Staff

Hiromichi RYUTO

Hiromichi RYUTOJunior Associate Professor (Graduate School of Engineering)

Research Interests

  • Production and transportation of heavy-ion beams
  • Interaction between heavy-ion beams and materials
  • Bioscience using heavy-ion beams


Room A1-112, Kyoto University Katsura Campus
TEL: +81-75-383-2339
FAX: +81-75-383-2343
E-mail: ryuto


Mitsuaki TAKEUCHIAssistant Professor (Graduate School of Engineering)

Research Interests

  • Multi atom molecular ion beam
  • Extremely low energy ion beam
  • High-performance thin film engineering


Kyoto Univ. Katsura Campus A1-112
TEL: +81-75-383-2339
FAX: +81-75-383-2343
E-mail: m-takeuchi

Introduction to R&D Topics

Cluster formation by nozzle beam method

We have successfully produced nano-sized clusters such as liquid and gas clusters utilizing the adiabatic expansion phenomenon, by injecting vapors into a vacuum from a nozzle, at a vapor pressure of several atmospheres. In addition to clusters of water and other liquids, we have so far produced clusters of argon, oxygen, and various other gases. Furthermore, we used the retarding electric field method and time-of-flight mass spectrometry (TOF-MS) to measure the number of molecules that make up a single cluster (cluster size), finding that clusters range in size from hundreds to tens of thousands of molecules. The formed nano-sized particles (clusters) are attracting much interest as new materials exhibiting different physical and chemical properties to materials in a bulk state—for example, a material that is made of water, but has properties that are unlike those of normal water.

Cluster ion beam processes

The interaction between cluster ions and solid surfaces is a multiple collision process, having durations ranging from picoseconds to nanoseconds. The irradiation area of a single cluster ion on a solid surface is extremely small—on the order of nanometers. Accordingly, surface smoothing becomes possible at the nano level due to the high sputtering rate and lateral sputtering effect resulting from the high-density irradiation effect and the multiple collision effect, which cannot be achieved with conventional monomer ion beams. On top of this, it is possible to suppress the damage to the irradiated surface, due to the extremely-low energy irradiation effect. Particularly, in the case of liquid cluster ion irradiation, it is possible to control the hydrophilic/hydrophobic and lubricant properties of material surfaces and also to modify irradiated surfaces through addition and substitution reactions by combining high-speed etching and surface smoothing, as well as the chemical properties of the liquid cluster. Recently, in the cleaning processes used in semiconductor production, water and alcohol are indispensable for cleaning the surfaces of materials, but they cannot be used in etching. As described, however, cluster ion beam techniques have tremendous potential for their ability to overcome the limitations of conventional wet processes.

Development of new advanced functional materials

In recent years, the density and level of integration of electronic devices continues to increase relentlessly. It is also becoming increasingly important to create advanced functional materials—not only by controlling the general properties of the material, but by controlling the characteristic of its surfaces and interfaces at the atomic level. As a material processing technology at the atomic and molecular level, cluster ion beam techniques can be utilized usefully to a wide range of engineering and biochemical applications. For example, it can be applied beneficially to the invention of valuable new photocatalytic materials and biomaterials. If we make a comparison with thin films made with the conventional sol-gel method, we observe better flatness of material surfaces at the nano-level, improved adhesion to substrates, and an ability to produce more uniform advanced functional thin films. Thus, cluster ion beam processes represent an innovative and important materials process technology.