【提出用】

Crystal, Quasicrystal, and Amorphous

Ce311

E DEDAGAWA
A G A W A LAB.
LAB.
Orderin 室Atomic※研究名 の みArrangement
入 力 く だ さ andいPhysical Properties of Solids
Research Center for Sustainable Material Energy Integration
Department of Fundamental Engineering
Mechanical Properties of Materials
Department of Materials Engineering, Graduate School of Engeneering

http://www.edalabo.iis.u-tokyo.ac.jp

If we look into solids microscopically, we find that atoms are arranged in some ordered manner. Microscopic
structures in solids can be classified in view of the atomic order into three groups: periodic structures(crystals), quasiperiodic structures (quasicrystals) and amorphous structures. Such atomic orders often
determine the macroscopic properties of solids. We aim at elucidating the relation between the microscopic
structure and macroscopic physical properties of solids, and also at developing new materials with desirable
properties using the information obtained through such studies.

Photonic and Electronic Properties ofDislocations in Semiconductors

The local electronic behavior may change due to existence ofdislocations which are a kind of disturbance in atomic arrangement
induced by plastic deformation. We observed some related
phenomena such as conductive spots on the surface ofsemiconductors and the shifts in optical absorption edge.

Physical Properties Inherent to Quasicrystals

Quasicrystals, which have both the long-rangeorder of the atomic arrangement and therotational symmetry that is unallowable forcrystals, show some unique properties. We
observed the anomalous increase of specific heatat high temperature.
Also, the growing mechanism of quasicrystals is
still unknown because their structure is notdescribed by the simple repetition of a unit cell.
Our high-temperature in-situ HRTEM observation
showed the dynamic process of quasicrystal
growth under a specific condition.

Change in optical absorption
spectra by plastic deformation

Conductive spots on surface of GaN
introduced by plastic deformation

τ3

τ
1

τ2

Electron diffraction pattern of
Al-Cu-Fe icosahedral quasicrystal
with the incident beam parallel
to a fivefold axis

Braking of Dulong-Petit’s
law in high-temperature
specific heatIn-situ TEM observation ofAl-Ni-Co icosahedral quasicrystal growth

Development of Random Network Photonic Devices
In an artificial structure of dielectrics designed in asuitable manner, it is known that the electric wave in acertain wavelength region cannot propagate. Such region
as known as 'photonic band gap' arises for the analogicalmechanism of electric band gap arising in an ordered
atomic arrangement. Although it was thought that only
periodic structures shows those property, our laboratory
showed that the same phenomena can be realized evenin a certain type of amorphous structure.
We fabricated the specimens for millimeter- andterahertz-wave regime by the 3-D manufacturing andsintering technique, and observed a large drop in thetransmittance spectrum at corresponding region to thephotonic band gap.

PADPAD

PCD

PCD(Upper) structural models expected to have photonic bandgap. (Lower) fabricated photonic structures in a terahertz
regime. (Left) amorphous structure and (right) crystalline
structure, respectively.

Measured electric wave
transmittance spectra interahertz regime of fabricated(upper) amorphous structureand (lower) crystalline
structure.