Study of C60 thin films by scanning tunnelling microscopy: pressure-induced transformation to an amorphous carbon phase

A scanning tunnelling microscope is used to exert pressure in the GPa range to a fullerene C60 thin film on Au(111) by operating the microscope at a tunnelling current of 40 nA and a bias voltage of 4 mV. The fullerene molecules are locally transformed into a disordered carbon phase. Pair and angular distribution functions based on scanning tunnelling microscopy (STM) images on the atomic scale confirm the presence of an amorphous structure with a nearest-neighbour distance of 0.28 nm and a second-nearest-neighbour distance of 0.37 nm. The protrusions resolved in the STM images are interpreted as carbon rings.