ABSTRACT

It is well known that the size of integrated circuit chips has followed Moore's law of shrinking transistor dimensions since the 1960s [1]. But transistors cannot be scaled down infinitely; in recent years, the gate size is approaching the ten-nanometer scale, which is close to the size of a large molecule. Therefore, nanometer-sized molecular systems on a surface, as a step towards the realization of molecular electronic devices, are being widely explored in order to overcome the fabrication limit of silicon-based devices [2,3]. The challenge is to prepare new functional materials and to construct well-defined nanometer-sized structures on solid surfaces by self-assembly [4,5]. A two-dimensional (2D) and three-dimensional (3D) topological organization of molecules through metal coordination has led to the development of new metal-organic frameworks in crystal engineering [6,7]. The various frameworks have been constructed by the crystallization of molecular modular units from solutions [8]. On the other hand, molecular assembly at a solid surface makes supramolecular structures at the surface, which have been called self-assembled monolayers (SAM). It is wellknown that organic thiols have been self-assembled on a gold surface, and the resulting monolayer films make it possible to control the surface functionality such as wettability, redox activity, photochemical response, etc. On the top of SAM monolayer, another layer can be grown by use of various interactions such as electrostatic interaction, hydrogen bonding interaction, and coordination bonding (Scheme 1).