• Nakagawa group has dedicated to pursue scientific principles for molecular control of interface function occurring at polymer/other material interfaces and to put them into practice in nanoimprint lithography promising as a next generation nanofabrication tool. We are developing advanced photo-functional materials such as sticking molecular layers for "fix by light", UV-curable resins and antisticking molecular layers for "preparation by light", fluorescent resist materials for "inspection by light", and hybrid optical materials "available to light" and new research tools such as mechanical measurement systems to evaluate release property of UV-curable resins.

Our research aims at creating new devices to control photon, electron, and magnetism.

• Electronic products can be operated not only by semiconductors but also by metal interconnections attached to the semiconductors. Required properties for the metal interconnections are ohmic contact, diffusion barrier property, adhesion with semiconductors, and low resistivity, corrosion resistance, process reliability. Our group has committed ourselves to develop new metals and processes to meet the needs of wide-ranged device producers with consideration of cost performance. Topics of our research include (1) Cu alloys to self-form a diffusion barrier layer in multilayer interconnection of Si devices, (2) Cu alloys to form a reaction-doping layer in IGZO oxide semiconductors, (3) Nb alloys to achieve mechanical and thermal reliability with good ohmic property for SiC power devices, (4) Cu alloys for transparent conductive oxide such as ITO, (5) screen-printable Cu paste lines for solar cells, etc..

Our research efforts are targeted at metallization and interconnections for advanced LSI, flat panel displays, touch panels, power modules, solar cells, and other electronic devices. Collaborators include material producers, equipment vendors, and device producers in the entire value chain of electronic products.

We aim to give high thermal conductivity to glass, which is known as a material that does not conduct heat well, and to apply it to new fields.

If mixed with a high thermal conductive material, glass can be a good conductor of heat. However, all the advantages of glass, such as transparency and freedom of molding, are lost. In this research, we succeeded in developing a transparent glass with high thermal conductivity that retains its glassiness by adopting the strategies of high thermal conductivity MgO deposition and refractive index matching.

• Transparent
• Free molding
• Thermal conductivity ~ 3 W/(m K) [300% of that of window glass]

Heat dissipation management using glass [heat dissipating glass substrates, lenses, fibers, etc.]

Nitride semiconductor free-standing substrate production method
https://www.t-technoarch.co.jp/data/anken_en/T14-121.pdf
This invention relates to a technique for producing high-quality nitride semiconductor freestanding substrates at a lower cost. The invention also includes the use of SCAlMgO4 substrates as seed crystals. The dislocation density of nitride semiconductors on this substrate becomes lower. By controlling the crystal polarity, the crystal diameter can be expanded as well as the thickness of the nitride semiconductor.

It is possible to fabricate freestanding nitride semiconductor substrates with lower through-dislocation density than conventional substrates. Furthermore, the cleavage property of ScMgAlO4, which serves as the substrate, facilitates the exfoliation of the nitride semiconductor and reduces the cost of substrate fabrication.

• Usage of ScAlMgO4 as a source substrate.
• Expansion of crystal diameter by using N-polar growth
• When ScAlMgO4 is used as the seed crystal and AlN is formed as the surface protective layer of this crystal, the surface shall be further nitrided after oxidation of the surface.
• The main surface of the seed crystal shall be inclined 0.4 to 1.2° from the c-plane.

This invention is to provide high-quality, low-cost free-standing nitride semiconductor substrates for optical devices such as light-emitting diodes and lasers, and transistors operated under high power, high voltage, and high frequency. Companies are expected to verify the commercialization of the product.

We have developed a technique for quantitative analysis of microstructures (e.g., dislocations and irradiation defect aggregates) of activated and nuclear-burned specimens in the context of the Week Beam Scanning Transmission Electron Microscope (WB-STEM) method, which boasts extremely high measurement accuracy as a quantitative analysis method for lattice defects.
In combination with a dedicated heated sample holder with fully automated temperature measurement and current control in a cartridge-type heating furnace, changes in dislocation microstructure can be dynamically measured in-situ along with a highly reliable temperature history.

Conventional TEM methods require expertise in reciprocal space and dislocation theory, but our WB-STEM method is equipped with automatic analysis software for film thickness measurement and dislocation loop feature extraction, making it possible to analyze irradiation defects easily and precisely.

• Since its design, the WB-STEM method has been developed for implementation and on-site repair in radiation controlled areas where nuclear materials are handled, with special aperture and diffraction disc selection equipment, control and analysis software.
• WB-STEM accepts irradiation defect analysis of activated specimens from all over the world, including RPV monitoring specimens from European reactors and neutron-irradiated materials from US research reactors.
• It is also used to analyze the properties of iron-containing nuclear fuel simulated debris in decommissioning projects.

We support research organizations that currently use transmission electron microscopy to observe microstructures to introduce the WB-STEM method by special modification. We will instruct researchers who have no experience using transmission electron microscopy in the procedure for dislocation analysis.

• This group is engaged in basic and applied researches of "hydrides" for practical use in hydrogen energy system. The main subject is the exploration of advanced hydrogen storage materials which support hydrogen energy technologies such as fuel cells. Currently, we synthesize a wide variety of novel hydrides composed of lightweight metals with specific nano-structures using advanced techniques for crystal and electronic structure analyses. In addition to the hydrogen storage, we develop the wide research fields related to hydrides, such as fast lithium ionic conductors.

Besides the contributions in industrial progress through the material development for future hydrogen energy system and next-generation secondary battery, we positively provide technical assistance to organizations and companies concerned about our findings.