Overview of Materials Science Research

Hideaki Takayanagi
Materials Science Laboratory

The Materials Science Laboratory (MSL) aims at discovering new quantum phenomena and creating new concepts by producing new materials. Toward these goals, the following five research groups of MSL investigate various materials, ranging from inorganic ones such as high-Tc superconductors and photonic crystals to organic materials like silicon polymers and biopolymers. Another important feature of MSL is the effective sharing of nanofabrication and precise measurement techniques developed originally in each group. This could possibly open new fields in global information sharing markets.

(1) Molecular Science Research Group
Research into high-luminescent optical devices and new-functional electron devices using new organic materials.
(2) Bio-Science Research Group
Research into information processing devices using a novel architecture based on neural function.
(3) Superconducting Thin Films research Group
Development of thin-film growth technology for high-Tc superconductors using molecular beam epitaxy method.
(4) Superconducting Quantum Physics Research Group
Research into Andreev reflection in superconductor/semiconductor junctions and macroscopic quantum coherence in superconducting devices for the application to q-bits.
(5) Nano-Structure Materials Research Group
Development of optical devices with unique beam propagation using the fabrication technology of three-dimensional photonic crystals.

Three major results obtained in fiscal year 1999 are reported in the following pages. The first topic is about the control method of the screw-pitch of herical polysilane copolymers (Topic 1). We found that diarylpolysilylene undergoes a reversible, thermo-driven helix-helix transition with a transition temperature of -10C. The obtained result could potentially find application in a two state, switchable material.
A new superconducting lead cuprate was prepared by molecular beam epitaxy (MBE) method (Topic 2). A reduction of the synthesis temperature in MBE makes it possible to synthesize a thin film which can not be prepared by conventional methods. Because the new cuprate contains one CuO2 layer, it has critical temperature (Tc) as low as 40 K. If we can synthesize this lead cuprate with three CuO2 layers, Tc higher than 120 K is expected.
Ferromagnetism in semiconductor dot arrays was theoretically predicted (Topic 3). Though the dots do not contain any kind of magnetic materials, the whole system shows ferromagnetism by changing the number of electrons in the dot. This controllability of magnetic states can lead to the possibility of new magnetic devices or switching ones.