Electronic Structure of TDAE−C₆₀ Complex

Abstract

Ultraviolet and C 1s and N 1s 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 1s 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.