Abstract:

A novel method is proposed to prepare an ordered array of pentacene adlayer on a Au(111) electrode by self-organization in benzene solution without using an ultra-high-vacuum (UHV) system. Because of the electron-rich characteristic, the pentacene monolayer acts as a template to incorporate electron-accepting fullerenes, forming a stable C₆₀/pentacene complex adlayer. The adlayer structure was investigated by an in situ scanning tunneling microscopy (STM). Two adsorbed structures, (√31 × √13) and (6 × √31), were observed for the pentacene adlayer. For the C₆₀/pentacene complex adlayer, molecular resolution STM revealed two ordered arrays, (2√3 × 2√3)R30° and “in phase” structures, for the C₆₀ molecules respected to the Au(111) substrate. The complex adlayer is stable between operational potential 0.35 and 0.9 V and is able to be decomplexed by selectively removing the fullerenes through the action of a high tip potential (0.75 V). The STM investigation also confirms that the complexation is performed by forming a C₆₀/pentacene/Au(111) nanoarchitecture. Scanning tunneling spectroscopy (STS) analysis reveals a semiconductive characteristic on pentacene and a rectifying behavior on the C₆₀/pentacene complex.