Substrate temperature effects on the electron field emission properties of nitrogen doped ultra-nanocrystalline diamond

• Published in: Diamond and related materials Vol. 17; no. 4; pp. 457 - 461
• Main Authors: Chen, Y.C., Tai, N.H., Lin, I.N.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 01.04.2008; Elsevier
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Electron and ion emission by liquids and solids; impact phenomena; Exact sciences and technology; Field emission, ionization, evaporation, and desorption; Fullerenes and related materials; diamonds, graphite; Ion and electron beam-assisted deposition; ion plating; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; MPECVD; Nitrogen doped; Physics; Specific materials; UNCD; UNCD; Nitrogen doped; MPECVD; Grain boundaries; Methane; Crystal defects; Electronic properties; Electrical conductivity; Electronic conductivity; Synthetic diamond; Doped materials; Secondary ion mass spectrometry; Carbon; Electron field emission; Thin films; CVD; Ultrananocrystalline diamond; Electronic structure; Temperature effects; Nitrogen additions; Current density; Microwave discharge; Plasma deposition
• ISSN: 0925-9635; 1879-0062
• DOI: 10.1016/j.diamond.2007.10.020

For the purpose of improving the electron field emission properties of ultra-nanocrystalline diamond (UNCD) films, nitrogen species were doped into UNCD films by microwave plasma chemical vapor deposition (MPCVD) process at high substrate temperature ranging from 600° to 830 °C, using 10% N 2 in Ar/CH 4 plasma. Secondary ion mass spectrometer (SIMS) analysis indicates that the specimens contain almost the same amount of nitrogen, regardless of the substrate temperature. But the electrical conductivity increased nearly 2 orders of magnitude, from 1 to 90 cm − 1 Ω − 1 , when the substrate temperature increased from 600° to 830 °C. The electron field emission properties of the films were also pronouncedly improved, that is, the turn-on field decreased from 20 V/μm to 10 V/μm and the electron field emission current density increased from less than 0.05 mA/cm 2 to 15 mA/cm 2. The possible mechanism is presumed to be that the nitrogen incorporated in UNCD films are residing at grain boundary regions, converting sp 3-bonded carbons into sp 2-bonded ones. The nitrogen ions inject electrons into the grain boundary carbons, increasing the electrical conductivity of the grain boundary regions, which improves the efficiency for electron transport from the substrate to the emission sites, the diamond grains.