The reaction of solid films with atomic deuterium to yield deuterofullerenes, , has been investigated by thermal desorption spectroscopy coupled with mass spectrometric detection, ultraviolet photoionization spectroscopy , 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 cages. Saturation exposures at room temperature yield mass spectra peaked at . After saturation exposures at elevated surface temperatures , the (subsequently) desorbed material reveals a comparatively narrow mass spectral distribution centered at . Deuteration is associated with cleavage of covalent cage-cage bonds in the starting oligomer material, as evidenced by a considerable lowering of the sublimation energies of compared to desorption of desorbed from pure oligomer films. Correspondingly, AFM images reveal a D-induced, thermally activated transition from dendritic oligomer islands into smooth-rimmed islands composed of deuterated cages. Deuterated films exhibit a significantly lower work function than bare films. Progressing deuteration also gradually raises the surface ionization potential.
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Note: means the fraction of surface area covered by as measured by using of AFM, i.e., it represents the 2D projection of in fact, the three dimensional (3D) islands onto the HOPG substrate. The mean coverage reached in experiments depends strongly on the lateral density of surface imperfections (lattice defects, step edges, etc.) which act as nucleation centers.
