High performance n-channel organic field-effect transistors and ring oscillators based on C60 fullerene films

Abstract

We report on organic $n$ -channel field-effect transistors and circuits based on ${\mathrm{C}}_{60}$ films grown by hot wall epitaxy. Electron mobility is found to be dependent strongly on the substrate temperature during film growth and on the type of the gate dielectric employed. Top-contact transistors employing $\mathrm{Li}\mathrm{F}∕\mathrm{Al}$ electrodes and a polymer dielectric exhibit maximum electron mobility of $6{\mathrm{cm}}^2∕\mathrm{V}\mathrm{s}$ . When the same films are employed in bottom-contact transistors, using $\mathrm{Si}{\mathrm{O}}_2$ as gate dielectric, mobility is reduced to $0.2{\mathrm{cm}}^2∕\mathrm{V}\mathrm{s}$ . By integrating several transistors we are able to fabricate high performance unipolar ($n$ -channel) ring oscillators with stage delay of $2.3\mu \mathrm{s}$ .