Fabrication of Charge-Transfer Complex Nanocrystals Toward Electric Field-Induced Resistive Switching

Charge-transfer complex exhibits versatile characteristics such as optical properties, conductivity, and magnetism. The physicochemical properties can be controlled through molecular design combining various kinds of electron donors and acceptors. In particular, the degree of charge-transfer γ and the composition ratio of electron donor to acceptor are important factors to determine physicochemical properties. On the other hand, nanocrystallized charge-transfer complex would lead to unique properties, being different from both isolated molecule and bulk crystal. However, the reprecipitation method for common organic nanocrystals cannot be employed due to low solubility of charge-transfer complex in common organic solvents. Therefore, novel nanocrystallization method for charge-transfer complex should be developed. In this chapter, nanocrystallization involving doping process of charge-transfer complex, copper 7,7,8,8-tetracyanoquinodimethane (Cu-TCNQ), will be introduced in detail towards nanoelectronics application. Cu-TCNQ is typical Mott insulator and indicates a unique resistive switching behavior. It is expected that Cu-TCNQ nanocrystals with an excess amount of Cu, namely doped Cu-TCNQ nanocrystals, would show unique resistive switching behavior because of the degree of charge-transfer γ different from bulk crystal.