Wavelength dependence of the photoinduced indentation hardening in C60 crystals

Abstract

The photoinduced indentation hardening of C60 crystals was investigated in ultraviolet-visible light. The hardening strongly depended on the wavelength of the illumination light: the magnitude increased with increasing wavelength, and then reached a maximum at 700 nm. This indicated that red light is more effective than ultraviolet light in the hardening. The wavelength dependence of the hardening is discussed in terms of an interplay between the effective depth of the photoinduced polymerization and the penetration depth of the indenter.

PHOTOINDUCED HARDENING AND REDUCTION OF DISLOCATION MOBILITY IN C60SINGLE CRYSTALS: THE WAVELENGTH DEPENDENCE

“…5. Our measurements and data (5) show that the threshold photon energy, at which measurable photoinduced effects arise, is about 1.5-1.6 eV. The magnitude of the effects linearly increases with increasing the photon energy.…”

“…Photopolymerization of C 60 appears also in air (4)(5)(6). Light-irradiated in air C 60 becomes insoluble in common solvents, exhibits higher hardness compared to pristine fullerite and reverts to pristine fullerite after heat treatment at 400-500 K (4-7).…”

“…The aim of the present work was to investigate the wavelength dependence of phototransformation of C 60 single crystals in air using indentation hardness and dislocation mobility methods. The microindentation as a structure and depth sensitive test has been successfully used earlier in studies of the light-, atmosphere-, pressure and temperature-induced effects in fullerite (4,5,(7)(8)(9)(10)(11)(12). Investigations of the dislocation zone around indents can provide important information about photoinduced processes in the subsurface layer (7,11,13).…”

Photo-assisted growth of C 60 nanowhiskers from solution

“…In addition, it has been reported that the red light around 600 nm also occurs in the photo-induced hardening of C 60 crystals [15]. The specific red light appears to give rise to significant illumination effect on both of C 60 solution and solid.…”

Temperature and photopolymerization effects in microhardness of C70 crystals

“…[4][5][6][7] The light effect is a so-called photoillumination hardening. 4,5 The characteristics of the hardening are as follows. ͑1͒ The hardness increases with the development of the illumination time and reaches a constant value.…”