Amorphization of C60 fullerite by applying pressure in the GPa range using a scanning tunneling microscope:: Observation of transitions and aging

Fullerene molecules of a few monolayers thick C-60(111) film on Au(111) supported on mica, have been exposed to a pressure of approximate to 20 GPa by using the tip of a scanning tunneling microscope (STM) operated at 40 nA and 4 mV. Subsequent imaging at 0.7 nA and - 11 mV shows that this pressure has induced a transformation of C-60 fullerite into an amorphous structure with a nearest neighbour distance of 0.28 nm. The time evolution of this structure within approximate to 90 min reveals formation of nanocrystalline domains, their transformation into square eight-membered closed ring structures, and the breaking-up of these rings initially zig-zag, and then finally straight chains. Assignment of pentagon and hexagon carbon rings to the observed arrangements of protrusions is a possible explanation. Pair distribution and angular distribution functions are calculated based on the position of the protrusions extracted from the images. (C) 1997 Elsevier Science Ltd.