ELECTRICAL AND DEFECT PROPERTIES OF SN-DOPED C-60 THIN-FILMS

Tin-doped C-60 thin films have been prepared by co-evaporation. Throug h controlling the temperature of the boat containing Sn, C-60 thin fil ms with different Sn content have been obtained. The electrical and de fect properties of these Sn-doped C-60 films have been studied using r esistivity, Hall effect and electron spin resonance (ESR) measurements . Besides the ESR signal of g=2.0024 normally observed for all the und oped C-60 materials, a new signal was observed for all the doped C-60 films. The g factor and peak-to-peak linewidth of the new signal are 7 .0003 and 1.12 G, respectively. The spin density of the new signal inc reases with increasing Sn content. The temperature dependence of the e lectrical resistivity of these Sn-doped C-60 films shows semiconductin g behaviour in the temperature range from 20 to 420 K. The room temper ature conductivity increases with increasing Sn content and the activa tion energy at room temperature decreases with increasing Sn content. Hall effect measurements indicated that the conduction type in these S n-doped C-60 thin films is n-type. Fourier transform infrared absorpti on measurements verified that Sn atoms have indeed been incorporated i nto these Sn-doped C-60 films. (C) 1997 Elsevier Science Ltd.