Formation of cluster-assembled carbon nano-foam by high-repetition-rate laser ablation

High-repetition-rate laser ablation and deposition of carbon vapours results in the formation of quite different carbonaceous structures depending on the pressure of the ambient Ar gas in the chamber. Diamond-like carbon films form at a pressure below ≈0.1 Torr whereas a diamond-like carbon nano-foam is created above 0.1 Torr. Although laser-deposited amorphous carbon films have been extensively investigated in the past, here we present what, to our knowledge, is the first report of the production of a granular low-density carbon nano-foam with rich fraction of sp3 bonding. The bulk density of various foam samples was in the range (2–10)×10-3 g/cm3, and the specific surface area was 300–400 m2/g. The resistivity of the foam measured at low-voltage (±30 V) is (1–3)×109 Ohm cm at room temperature and (1–10)×1013 Ohm cm at 80 K. The dc conductivity of this low-density carbon foam and its temperature dependence appears to be very close to that of RF-sputtered solid amorphous diamond-like carbon films.