Superhard and superelastic films of polymeric C-60

The C-60 thin film deposited on steel substrate was transformed by high pre ssure-high temperature treatment to a superhard and superelastic material. The films were studied by Raman spectroscopy in situ at 20 GPa after heatin g at 300 degreesC and ex situ after the quenching. The hardness and elastic properties of the high-pressure phases have been characterized with nanoin dentation. The hardness of the films were determined to be 0.5 +/- 0.1 GPa and 61.9 +/- 9 GPa for unmodified C-60 and HPHT treated films, respectively . The hardness of the pressurized film is higher than for cubic BN but lowe r than hardness values reported for ultrahard fullerite samples prepared fr om powders. An interesting observation was that the HPHT treated film showe d an extreme elastic response with an elastic recovery of approximately 90% . (C) 2001 Elsevier Science B.V. All rights reserved.