Ionic liquid-mediated epitaxy of high-quality C ₆₀ crystallites in a vacuum

Ionic liquid-mediated vacuum deposition was demonstrated as a novel growth technique for high-quality C ₆₀ crystallites. In this process the ionic liquid worked as a solvent, i.e. the gas phase C ₆₀ precursors were continuously fed into the ionic liquid on a substrate in a vacuum chamber, from which the nucleation and the subsequent growth of C ₆₀ crystallites proceeded. The impact of varying the substrate on the growth behaviour was intensively examined in terms of not only the lattice-mismatch between C ₆₀ and the substrates, but also the wetting behavior of the ionic liquid on the substrates. This led to a significant improvement of the C ₆₀ crystallinity and epitaxial growth was successfully found on certain substrates. In particular, molecularly smooth and thick C ₆₀ hexagonal-shaped crystallites epitaxially grew on a MoS ₂ substrate, the average size of which reached as large as 10 μm.