Anion adsorption driving 2D crystallization of C60 at the ionic liquid [bmim][PF6]/Au(1 1 1) interface

The two-dimensional (2D) crystallization of C60, driven by the anion adsorption, at the [bmim][PF6]/Au(1 1 1) interface has been investigated by in situ scanning tunneling microscopy (STM). It is found that although a number of small ordered domains of C60 exist in air, they will gradually merge into some big ones in [bmim][PF6]. The formation of a high-quality epitaxial C60 film is attributed to the slow replacement of C60 by the PF6 adsorption and the high mobility of C60 on PF6/Au(1 1 1), i.e., a competitive adsorption–desorption process between C60 and PF6. Such strategy could be used to prepare epitaxial films of functional molecules.