• This lab is concerned with the novel approach mainly for the growth from melt by studying the relationship between the interface dynamics during growth and properties of grown crystals. Special interests lie in the growth of new crystals via the imposition of an interface-electric field. Nano-scaled control of crystal growth is executed in an electric double layer of ~nm thickness that is induced by applying an external electric field on the growth interface. Some of our growth results brought by applying an electric field are;
• 1. Growth of Langasite-type crystals for the pressure sensor at high temperature by manipulating the energy relationship between crystal and melt.
• 2. Easy nucleation of protein crystals that are normally hard to crystallize.
• 3. Formation of Si crystals with desired structure by manipulating the interface instability of Si.
• Crystals developed this way will widen an opportunity to collaborate with industries in the field of the piezoelectric, magnetic, optic and other fields related to the highly-networked information society.

• The main research subject of our group is developing material purification methods, crystal growth methods and detector fabrication technologies for compound semiconductor radiation detectors. Our group intensely studies a compound semiconductor, thallium bromide (TlBr), for fabrication of gamma-ray detectors for the advanced radiation applications. The attractive physical properties of TlBr lie in its high atomic number (Tl: 81, Br: 35), high density (7.56 g/cm3) and wide bandgap (2.68 eV). Due to the high atomic number and high density, TlBr exhibits high photon stopping power. The wide bandgap of TlBr permits the device low-noise operation at and above room temperatures.

Our group focuses on development of compound semiconductor radiation detectors for advanced radiation applications including ultra-high resolution PET systems, ultra-high resolution SPECT systems, photon counting CT systems and Compton cameras. We hope to conduct collaborative research with a willing company for a practical application of this technology in industry.

• Fukuyama laboratory studies novel material processing based on chemical thermodynamics with high-temperature thermophysical property measurements. As examples, we are developing new crystal growth processes to bring a breakthrough in nitride-semiconductor devices, which are promising materials for next-generation optical devices applied in environmental, medical, bio and information technologies fields. Database of thermophysical properties of materials is needed for modeling heat and mass transports in materials processes.

A new thermophysical property measurement system is currently under development, which enables accurate measurements of heat capacity, thermal conductivity, emissivity, density and surface tension of high-temperature melts, utilizing electromagnetic levitation in a dc magnetic field.

• 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.

• Conventional X-ray imaging methods that rely on X-ray attenuation cannot generate clear contrast in the observation of low-density materials such as polymers consisting of low-Z elements. However, the sensitivity to the materials can be improved drastically by X-ray phase imaging that detects X-ray refraction caused by the materials. X-ray Talbot or Talbot-Lau interferometry consisting of X-ray transmission gratings is now constructed in laboratories for X-ray phase imaging. X-ray phase tomography is also realized, enabling high-sensitive three-dimensional observation.
• X-ray phase imaging can be utilized for X-ray non-destructive testing of industrial products and baggage that cannot be checked conventionally.

We aim at appending a phase-contrast mode to micro-CT apparatuses and developing screening apparatuses in production lines.

• We successfully realized millisecond-order X-ray phase tomography using a fringe-scanning method in grating-based X-ray interferometry. We obtained phase tomograms with a measurement time of 4.43 ms using a white synchrotron X-ray beam. The use of a fringe-scanning method enables us to achieve not only a higher spatial resolution but also a higher signal-to-noise ratio than that attained by the Fourier transform method. In addition, our approach can be applied to realize four-dimensional or high-throughput X-ray tomography for samples that can be rotated at a high speed.

• For producing a new functionality from metallic micro and nano matarials, the welding and cutting technologies for small scale materials utilizing Joule heat has been developed (Fig. 1). A constant direct current is supplied to the system, where the free ends of two metallic wires are contacted, and the ends are successfully welded together in self-completed manner. This technology is also useful for manipulating a small scale materials.

Joule heat welding technology enables us to produce the functional elements on the electrode chips, e.g., a free-standing micro-ring and very-thin thermoelectric element (Fig. 2). Moreover, we have developed the technique for characterizing the physical properties of small scale materials (Fig. 3). We hope to conduct collaborative research with a willing company for a practical application of this technology in industry.

• We develop technology of the cyclotron accelerator and its application as follows. 1)Ion source (particularly heavy ion source), 2)design of ion optics, 3)device control system for the cyclotron, 4)RF system, 5)detectors for charged particles, gamma ray, and neutron, 6) radiation test by ion and neutron beam.

We have beam lines dedicated to the neutron irradiation and the ion irradiation, respectively. We can provide fast neutron beam (20-70 MeV), and various ion beam such as p, alpha, and heavy ions up to Xe. We also develop a neutron imaging technique using fast neutron.