Electronic structure of TDAE-C-60 complex

Ultraviolet and C Is and N Is X-ray photoelectron spectra of a ferromagnetic charge-transfer complex, TDAE-C-60, where TDAE is tetrakis(dimethylamino)ethylene, have been measured. The appearance of a new peak above the highest occupied band of C-60 at 1.2 eV below the Fermi level with a peak onset of 0.5 eV indicates that an electron is transferred from TDAE to C-60 and that TDAE-C-60 is not metallic but semiconductive. The N Is core spectrum of the complex shows a wide band consisting of two components, and the intensity of the higher binding energy one decreases under X-ray irradiation. The observed components could be ascribed to nitrogen atoms in TDAE(0) and TDAE(2+) on the basis of the electrostatic potential model in combination with the CNDO/2 molecular orbital calculation. Possible appearance of the charge density wave state along the TDAE chain in the c-direction of TDAE-C-60 crystal has been suggested.