Low-temperature annealing effect on electron field emission of tetrahedralamorphous carbon films

The low-temperature annealing effect on electron field emission of tetrahed ral amorphous carbon (ta-C) films was investigated. Ta-C films prepared by a filtered are deposition technique were annealed at 400 degrees C for 60-1 20 min in a nitrogen atmosphere. The density and sp(3) content in as-grown film were 3.3 g cm(-3) and similar to 90%, respectively. After annealing, n o obvious changes in film density or sp(3) content were observed. The thres hold electric field of electron emission of annealed ta-C films increased. Through annealing the clustering of sp(2) bonded carbon would occur, result ing in bandgap reduction and the eventual increase of the emission barrier. After a given annealing period, the degree of clustering increased, and wa s responsible for the threshold electric field increasing further. The resu lts implied that the control of the sp(2) bonding configuration in addition to the sp(3) bonding is important in obtaining good emission properties fo r ta-C films.