• Recently, many tunnel magnetoresistance devices with high magnetoresistance effect are reported. These are expected to be applied to high sensitive magnetic sensors. There are many magnetic sensors with variety of the mechanism, in order to meet the demand of the very wide range of sensing magnetic field. However, there is no magnetic sensor which has high sensitivity, easy to use, operation at room temperature and low cost. Only a magnetic sensor with tunnel magnetoresistance devices can satisfy all the demand in principle. As the device has very wide range of the sensing magnetic field, it can be designed for any demand to the sensors.

For example, this device can sense a bio-magnetic field easily at room temperature, so that it could be replaced SQUID device, which is popular now but is very expensive and not easy to use personally. Therefore, by using this device, we expect we can conduct effective collaborative research in medical field.

• It is well known that nano-scale impurity/solute clusters, defects, defect clusters and their complexes affect the mechanical and electrical properties in materials. However, it is very difficult to observe these objects even by state-of-the-art electron microscopes. We overcome the difficulty by employing noble two techniques: laser three-dimensional atom probe (3D-AP) technique and positron annihilation spectroscopy (PAS). Laser 3D-AP can map out each atom in various materials (metals, semiconductors, insulators) in three-dimensional real space with nearly atomic scale resolution. PAS can detect vacancy-type defects and defect-impurity complexes very sensitively.

By combining these methods, we are going to reveal the functions of the fine impurity clusters and defects to the materials: developments of new nano-structured materials, the mechanism of degradation of aged structural materials, the fall in the yield of semiconductor device production, and developments of quantum devices etc.

Colorful TiO2 Particle
https://www.t-technoarch.co.jp/data/anken_en/T19-849.pdf

Transition metal compounds are known to exhibit a wide variety of colors. Until now, it has been possible to color white titanium oxide by doping with transition metal ions, but it is difficult to avoid biotoxicity derived from transition metals.

• In the present invention, titanium oxide inorganic pigments that do not contain transition metals and have various colors such as white, yellow, red, gray, green, purple, black, and skin color have been realized.

New applications of titanium oxide pigments are expected in the cosmetics field, where biotoxicity is an issue.

• In our laboratory, miniature and highly-functional photonic devices based on new optical phenomena caused by the interaction of ultrafine microstructures with light have been studied. In addition, development of new production technology to overcome the problems that have been obvious from the practical application viewpoint of nanophotonic devices has been performed.
• • -Main research topics--
  MEMS tunable metamaterials for optical control.
• Structural color filters using subwavelength gratings for the applications of display and spectroscopic analyzers.
• Surface-smoothing technology using surface self-diffusion.
• Study of low loss silicon nanophotonic devices.

We aim to realize optical filters, optical resonators, and color filters, by using above technologies. Also, development of nano-photonic elements fabricated by a nanoimprint technology has been progressed.
We hope to conduct collaborative research with a willing company for a practical application of this technology in industry.

• Highly-sensitive NMR technique has been developed by manipulation polarization of nuclear spins via control of transport characteristics in GaAs and InSb quantum structures. This highly-sensitive NMR can be applied to two-dimensional and nanostructures. Furthermore, ideal gate controllability has been demonstrated in InSb quantum structures with Al2 O3 dielectrics. More importantly, the concept of generalized coherence time was introduced, where noise characteristics felt by nuclear spins can be measured including their frequency dependence. This concept will bring about a change in all nuclear-spin related measurements.

Next generation InSb devices based on good gate controllability. Various nuclear-spin based measurements and NMR utilizing the concept of generalized coherence time. Highly-sensitive NMR is now important for fundamental physics studies. In the future, it will contribute to quantum information processing.

• We challenge to fabricate in vacuum-stabilized micro/nano-scale liquid materials, explore their novel chemicophysical properties and develop their vacuum processing applications. The representative examples include ultra thin film ionic liquid on the nanometer scale and advanced vapor-liquid-solid growth (VLS) of inorganic/organic materials, such as 4H- and 3C-SiC films, single crystal pentacene and a porous polymer film of plolythiophene.

Our research outcomes will contribute to the following research and development:
1) a next-generation semiconductor process with the merits of the wet process
2) a new purification process of organic semiconductors, by which some part of inorganic semiconductor materials would be replaced in response to the present world-wide shortage of semiconductors.

In addition, the consultation of how to use our ionic liquid-assisted vapor growth method in attempt to obtain organic single crystals is welcome.

• Phase change random access memory (PCRAM) has attracted attention as next-generation non-volatile memories. A conventional PCM is Ge-Sb-Te which shows a fast crystallization speed and an excellent reversibility of phase transition. However, Ge-Sb-Te has a low crystallization temperature of about 150 ºC and a high melting temperature of over 600 ºC , which limits data retention and causes high power consumption, respectively.
• We have developed a new phase change materials with high crystallization temperature and low melting point such as Ge-Cu-Te etc, which have high potential as PCRAM materials with high thermal stability and low power consumption (Fig.1,2).

Our materials are developed for PCRAM, DVD recording materials etc. We hope the collaboration research with companies which are interested in our developed phase change materials.