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Title: Microstructural evolution of diamond films from CH{sub 4}/H{sub 2}/N{sub 2} plasma and their enhanced electrical properties

The influence of N{sub 2} concentration in CH{sub 4}/H{sub 2}/N{sub 2} plasma on microstructural evolution and electrical properties of diamond films is systematically investigated. While the diamond films grown in CH{sub 4}/H{sub 2} plasma contain large diamond grains, for the diamond films grown using CH{sub 4}/H{sub 2}/(4%)N{sub 2} plasma, the microstructure drastically changed, resulting in ultra-nanosized diamond grains with Fd3m structure and a{sub 0} = 0.356 nm, along with the formation of n-diamond (n-D), a metastable form of diamond with space group Fm3m and a{sub 0} = 0.356 nm, and i-carbon (i-C) clusters, the bcc structured carbon with a{sub 0} = 0.432 nm. In addition, these films contain wide grain boundaries containing amorphous carbon (a-C). The electron field emission (EFE) studies show the best EFE behavior for 4% N{sub 2} films among the CH{sub 4}/H{sub 2}/N{sub 2} grown diamond films. They possess the lowest turn-on field value of 14.3 V/μm and the highest EFE current density value of 0.37 mA/cm{sup 2} at an applied field of 25.4 V/μm. The optical emission spectroscopy studies confirm that CN species are the major criterion to judge the changes in the microstructure of the films. It seems that the grain boundaries can provide electron conduction networks to transport efficiently the electrons to emission sites for fieldmore » emission, as long as they have sufficient thickness. Whether the matrix nano-sized grains are 3C-diamond, n-D or i-C is immaterial.« less
Authors:
;  [1] ;  [2]
  1. Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 300, Taiwan (China)
  2. Department of Physics, Tamkang University, Tamsui 251, Taiwan (China)
Publication Date:
OSTI Identifier:
22413142
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 117; Journal Issue: 7; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; BCC LATTICES; CARBON NITRIDES; CONCENTRATION RATIO; CURRENT DENSITY; DIAMONDS; ELECTRICAL PROPERTIES; ELECTRONS; EMISSION SPECTROSCOPY; FCC LATTICES; FIELD EMISSION; FILMS; GRAIN BOUNDARIES; HYDROGEN; MATRIX MATERIALS; METHANE; NANOSTRUCTURES; PLASMA