Coulomb expansion of a van der Waals C-60 solid film

Scanning tunneling microscopy study revealed a van der Waals C-60 solid fil m with 13% room-temperature lattice expansion on the GaAs(001) 2 x 4 surfac e. The mechanism involves fundamental Coulomb interaction due to charge tra nsfer from the GaAs substrate. Theoretical calculation determines the charg e transfer to be 1.76 electrons per C-60 molecule. Oriented at its (110) cr ystallographic axis this film also distinguishes itself from those formed o n all other semiconductor and metal substrates where only the low-energy (1 11) hexagonal packing of C-60 molecules was developed. It is shown that thi s is due to the one-dimensional confinement effect of the anisotropic subst rate, which may have the prospect of controlling crystal growth.