Field emission studies of low-temperature thermal annealing of nitrogen-doped hydrogenated amorphous carbon (a-C : H : N) films

Nitrogen-doped hydrogenated amorphous carbon (a-C:H:N) films have been depo sited by radio frequency plasma methods using N-2/CH4 gas mixtures. The eff ects upon optical and electronic properties of these films of low temperatu re (100-450 degreesC) annealing in vacuum (less than or equal to 1 x 10(-5) torr) for various times were then studied. Such annealing causes a decreas e in film thickness, probably due to evolution of species from the films, w hich is a function of annealing temperature and time. Laser Raman measureme nts show structural changes at 200 degreesC. Fourier transform infra-red sp ectra indicate no change in CH bonding below temperatures of 450 degreesC. Field emission results show that suitable post-treatment annealing at 200 d egreesC can reduce both the threshold field density and the threshold field by a factor of two. Annealed films also show an order of magnitude improve ment in emission current for a given threshold field density. We also find an increase in the gradient of current-electric field curves, which extend to higher electric field values with increasing duration of annealing and w ith temperature. (C) 2001 Elsevier Science B.V. All rights reserved.