Abstract
Conductivity and its temperature dependence, conduction type, and field-effect mobility in metal (In or Sb)-doped C60 thin films are investigated together with those of undoped films. All electrical measurements have been conducted without exposure to air after deposition, in order to minimize the degradation of films due to incorporation of oxygen. For films with both dopants, (1) the conductivity is several orders of magnitude higher than that of undoped films, (2) the conductivity follows a semiconductor-like temperature dependence with the activation energy of 0.10-0.17 eV, which is much lower than that of the undoped films, 0.51 eV, (3) the conduction is n-type, and (4) the field-effect mobility is 0.03-0.04cm2/V·s. Enhancement of conductivity in metal-doped C60 films is attributed to the increase of both carrier concentration and mobility.