Temperature dependence of the microhardness and dislocation mobility in the near-surface layer of C60 crystals

Temperature dependence of the Vickers microhardness and dislocation mobility of as grown and aged in air C-60 Single crystals in the range of 300-550K has been investigated. An anomalous change of the hardness in the near-surface layer of C-60 crystals around 470K is observed which is explained by the phase transition from an oxygen-intercalated to an oxidised structure. The growth of the oxide film on heating the crystals in air at temperatures higher than 470K is detected, and hardness of 280 MPa of the oxide film is measured. The stress-promoted oxidation of fullerite in the local zones of indentation at 390-470K is discovered. It has been found that ageing of the crystals in air reduce the temperature of the stress-promoted oxidation.