Deuteration-induced scission of C58 oligomers.

The reaction of solid C(58) films with atomic deuterium to yield deuterofullerenes, C(58)D(x), has been investigated by thermal desorption spectroscopy coupled with mass spectrometric detection, ultraviolet photoionization spectroscopy (21.2 eV), and atomic force microscopy (AFM). The average composition of the deuterofullerenes created depends on deuterium dose, beam flux, and surface temperature. Low deuterium exposures at room temperature yield predominantly C(58)D(6-8) cages. Saturation exposures at room temperature yield mass spectra peaked at C(58)D(26). After saturation exposures at elevated surface temperatures (approximately 500 K), the (subsequently) desorbed material reveals a comparatively narrow mass spectral distribution centered at C(58)D(30). Deuteration is associated with cleavage of covalent cage-cage bonds in the starting C(58) oligomer material, as evidenced by a considerable lowering of the sublimation energies of C(58)D(x) compared to desorption of C(58) desorbed from pure oligomer films. Correspondingly, AFM images reveal a D-induced, thermally activated transition from dendritic C(58) oligomer islands into smooth-rimmed islands composed of deuterated cages. Deuterated films exhibit a significantly lower work function than bare C(58) films. Progressing deuteration also gradually raises the surface ionization potential.