Electrical and defect properties of Sn-doped C60 thin films Original Research Article

Tin-doped C60 thin films have been prepared by co-evaporation. Through controlling the temperature of the boat containing Sn, C60 thin films with different Sn content have been obtained. The electrical and defect properties of these Sn-doped C60 films have been studied using resistivity, Hall effect and electron spin resonance (ESR) measurements. Besides the ESR signal of g = 2.0024 normally observed for all the undoped C60 materials, a new signal was observed for all the doped C60 films. The g factor and peak-to-peak linewidth of the new signal are 2.0003 and 1.12 G, respectively. The spin density of the new signal increases with increasing Sn content. The temperature dependence of the electrical resistivity of these Sn-doped C60 films shows semiconducting behaviour in the temperature range from 20 to 420 K. The room temperature conductivity increases with increasing Sn content and the activation energy at room temperature decreases with increasing Sn content. Hall effect measurements indicated that the conduction type in these Sn-doped C60 thin films is n-type. Fourier transform infrared absorption measurements verified that Sn atoms have indeed been incorporated into these Sn-doped C60 films.