Preparation of N-doped hydrogen-free diamondlike carbon and its application to field emitters

Abstract

We have studied the electrical, optical and field emission,properties of nitrogen gas-phase doped hydrogen-free diamondlike carbon (DLC) films. The N-doped hydrogen-free DLC films were deposited by an alternating layer deposition technique using plasma enhanced chemical vapor deposition, in which deposition of a thin layer of gas-phase doped DLC and CF4 plasma exposure on its surface were carried out alternately. The optical band gap of the DLC films decreases from 1.8 to 1.55 eV with an increase of the [N-2]/[CH4] ratio from 0% to 24% because of an increase of the graphite phase ( pi state). The emission current density and onset field are strongly related to the gas-phase doping concentration in the DLC films. The optimum [N-2]/[CH4] flow rate ratio for efficient electron emission,was found to be 9%. The onset held and the effective barrier energy at 9% are 7.2 V/mu m and 0.02 eV, respectively. The material appears to be modified into a carbon-nitrogen alloy when it exceeds 9%. We have also studied the enhanced field emission characteristics of nitrogen gas-phase doped hydrogen-free DLC films on Mo tip held emitter arrays. The maximum emission current for each pixel increased from 160 mu A to 1.52 mA with the addition of a 200 Angstrom thick N doped hydrogen-free DLC coating on the Mo tips. (C) 1999 American Vacuum Society. [S0734-211X(99)01601-7].