New Research


2009/04/01

Design in Nanometer Scale on a Surface

— Two-Dimensional Nano-Pattern Created by Aligning Four Molecular Components —

Professor Yoshito Tobe, Assistant Professor Kazukuni Tahara

In order to construct small integrated circuit (IC), a great deal of attentions has been focused on the bottom-up approach which makes it possible to create small surface patterns in few nano-meter scale instead of surface patterns in few 10 nano-meter scale constructed by the top-down approach such as electron beam lithography. In the case of surface pattern formation by the bottom-up approach, molecules, the size of which is ca. 1 nm, are used as component. Fine design of the molecular structure and its synthesis are required for successful control of molecular alignment on a surface. Moreover, the observation of molecular alignment with high accuracy by scanning tunneling microscope (STM) is also required. Therefore, multidisciplinary collaborative researches have been developing in worldwide.
We have focused on the research concerning the synthesis of planar molecules with various shapes to control their aggregation, so-called “self-assembly”, for the formation of various desinges in few nano-meter scales on a surface. Recently, we succeeded in making patterns as we wish on a graphite surface making use of four kinds of planer molecules, rhombus-shaped (green-colored), large hexagonal-shaped (orange-colored), small hexagonal-shaped (pink-colored), and triangular-shaped molecules. The above figure (up) displays schematic representation of the four-component pattern. In this system, the key for the success is use of porous structure so-called “Kagome” structure formed by rhombic molecules on graphite surface (the Kagome structure was introduced in latest research information updated at 2006.09.01). The Kagome structure contains both small triangular pore and large hexagonal pore. By recognizing size and shape of each pore, the triangle molecule is adsorbed in the triangular pore as well as six small hexagonal molecules and one large hexagonal molecule are adsorbed in the hexagonal pore. The above figure (down) shows an STM image of the four-component design. Each molecular component is fixed in the pores, and nano-pattern can be visualized clearly.
We have been engaged in the research work to create functional organic materials including not only 2D self-assembly systems described above but also development of molecular sensors and molecular machines based on molecular recognition event and the synthesis of novel giant pi-electronic systems and their self-association. For further detail, please visit our laboratory website at:


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