JAPAN NANONET BULLETIN - 11th Issue - February 5, 2004

YOUNG RESEARCHERS’ INTRODUCTION

Hisao YANAGI Research Associate, Department of Chemical Science and Engineering, Faculty of Engineering, Kobe University 1980 Bachelor, Faculty of Engineering, Kobe University 1982 Master, Faculty of Engineering, Kobe University 1980- 1984 Researcher, Nippon Shinyaku Co., Ltd. 1988 Ph. D.(Science), Graduate School of Science and Technology, Kobe University 1980- present  Research Associate, Faculty of Engineering, Kobe University 2000- 2003 Researcher, Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Corporation (JST) (Researche Area of “Structural Ordering and Physical Properties”) E-mail address:   WEB PAGE

  Electronic band structures play an important role in covalently bound crystals of inorganic semiconductor materials. A variety of optoelectronic devices have been developed based on their quantum effects using bulk downsizing technology. On the other hand, a bottom-up molecular organization is important for organic materials, in which molecules interact by weak van der Waals force, since their solid-state properties are basically ascribed to individual molecular characteristics.

  Moreover, molecular orientation in the solid-state strongly affects their properties due to a low-dimensional anisotropy of chainlike and planar molecules. This study aims at developing novel molecular electronic/photonic materials by low-dimensional ordered structuring of functional molecules across single-molecule, nanoscale and microscale ranges.

  To date, we have observed lasing actions from self-organized zero-dimensional microdots and one-dimensional nanoneedles of fluorescent p-conjugating oligomers based on the microcavity and self-wave guiding effects of light confined in these low-dimensional structures. Furthermore, a reversible flip-flop single-molecular switching phenomenon induced by scanning tunneling microscopy has been observed for two-dimensional monolayer arrays of ansymmetric, and polar subphthalocyanine molecules adsorbed on a metal surface in ultrahigh vacuum.

  We are now investigating their detailed mechanisms for the practical development of organic semiconductor lasers and high-density molecular information storage devices.

Fig. 1 Large Image Lasing actions from organic low-dimensional ordered structures. A) Light emission amplified by the microcavity effect of self-organized microdots with a distyrylbenzene derivative. B) Self-wave guided light amplification in epitaxially grown nanoneedles of p-sexiphenyl.

Fig. 2 Large Image STM-induced flip-flop switching of subphthalocyanine (SubPc) monolayer array adsorbed on Cu (100). In the as-adsorbed state, SubPc (A) molecules randomly arrange with its axial chlorine atom upwards (Cl-up) or downwards (Cl-down) (B,C). At varied sample bias voltages, the molecules switch to all Cl-up or all Cl-down state (D)