Nanoscale structural characteristics and electron field emission properties of transition metal-fullerene compound TiC_(60) films

摘要

Transition-metal compound TiC_(60) thin films were grown by co-deposition from two separated sources of fullerene C_(60) powder and titanium. Study of structural properties of the films, by Raman spectroscopy, atomic force microscopy, and scanning tunneling spectroscopy reveals that the films have a deformed C_(60) structure with certain amount of sp~3 bonds and a rough surface with a large number of nanoclusters. z-V tunnelling spectroscopic measurements suggest that several charge transport mechanisms are involved in as the tip penetrates into the thin film. Conventional field electron emission (FEE) measurements show a high emission current density of 10 mA/cm~2 and a low turn-on field less than 8 V/μm, with the field enhancement factors being 659 and 1947 for low-field region and high-field region, respectively. By exploiting STM tunneling spectroscopy, local FEE on nanometer scale has also been characterized in comparison with the conventional FEE, The respective field enhancement factors are estimated to be 99-355 for a gap varying from 36 to 6 nm. The enhanced FEE of TiC_(60) thin films can be ascribed to structural variation of C_(60) in the films and the electrical conducting paths formed by titanium nanocrystallites embedded in C_(60) matrix.