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Title: Origin of graphitic filaments on improving the electron field emission properties of negative bias-enhanced grown ultrananocrystalline diamond films in CH{sub 4}/Ar plasma

Microstructural evolution of bias-enhanced grown (BEG) ultrananocrystalline diamond (UNCD) films has been investigated using microwave plasma enhanced chemical vapor deposition in gas mixtures of CH{sub 4} and Ar under different negative bias voltages ranging from −50 to −200 V. Scanning electron microscopy and Raman spectroscopy were used to characterize the morphology, growth rate, and chemical bonding of the synthesized films. Transmission electron microscopic investigation reveals that the application of bias voltage induced the formation of the nanographitic filaments in the grain boundaries of the films, in addition to the reduction of the size of diamond grains to ultra-nanosized granular structured grains. For BEG-UNCD films under −200 V, the electron field emission (EFE) process can be turned on at a field as small as 4.08 V/μm, attaining a EFE current density as large as 3.19 mA/cm{sup 2} at an applied field of 8.64 V/μm. But the films grown without bias (0 V) have mostly amorphous carbon phases in the grain boundaries, possessing poorer EFE than those of the films grown using bias. Consequently, the induction of nanographitic filaments in grain boundaries of UNCD films grown in CH{sub 4}/Ar plasma due to large applied bias voltage of −200 V is the prime factor, which possibly forms interconnected paths formore » facilitating the transport of electrons that markedly enhance the EFE properties.« less
Authors:
;  [1] ; ;  [2] ;  [3]
  1. Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 300, Taiwan (China)
  2. Graduate Institute of Electro-Optical Engineering and Department of Electronic Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan (China)
  3. Department of Physics, Tamkang University, Tamsui 251, Taiwan (China)
Publication Date:
OSTI Identifier:
22308128
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 116; Journal Issue: 16; Other Information: (c) 2014 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; 77 NANOSCIENCE AND NANOTECHNOLOGY; CHEMICAL BONDS; CHEMICAL VAPOR DEPOSITION; CRYSTAL GROWTH; CURRENT DENSITY; DIAMONDS; ELECTRONS; FIELD EMISSION; FILAMENTS; GRAIN BOUNDARIES; GRAPHITE; MICROWAVE RADIATION; NANOMATERIALS; NANOSTRUCTURES; RAMAN SPECTROSCOPY; SCANNING ELECTRON MICROSCOPY; THIN FILMS; TRANSMISSION