N-type conductivity and phase transition in ultrananocrystalline diamond films by oxygen ion implantation and annealing

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

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  • X. J. Hu
  • J. S. Ye
  • H. J. Liu
  • X. H. Chen
  • H. Hu


Original languageEnglish
Article number53524
Journal / PublicationJournal of Applied Physics
Issue number5
Publication statusPublished - 1 Mar 2011


Ultrananocrystalline diamond (UNCD) films were implanted by oxygen ion and annealed at different temperatures. The electrical and structrual properties of O+-implanted UNCD films were investigated by Hall effects, high-resolution transmission electron microscopy (HRTEM) and uv Raman spectroscopy measurements. The results show that O+-implanted nano-sized diamond grains annealed at 800 °C and above give n-type conductivity to the sample and the UNCD film exhibits n-type resistivity with the carrier mobility of 1∼11 cm2 V-1s-1. With O+ dose increasing from 1015 to 1016 cm-2, diamond phase transits to the amorphous carbon phase accompanied by n-type semiconduction transforming to metallic conduction. In the 1014 cm-2 O+-implanted UNCD film, some amorphous carbon at grain boundaries transits to diamond phase with annealing temperature (Ta) increasing from 500 °C to 800-900 °C, and some of diamond grains are found to be converted to amorphous carbon phase again after 1000 °C annealing. This phase transition is closely relative to the n-type conductivity of the UNCD films, in which n-type conductivity increases with the amorphous carbon phase transiting to diamond phase in the Ta range of 500-900 °C, and it decreases with diamond phase transiting to amorphous carbon phase in the case of 1000 °C annealing. It is indicated that the O-implanted nano-sized diamond grains dominantly control the n-type conductivity of UNCD film in the Ta range of 800-900 °C, while the grain-boundary-conduction controls the n-type conductivty in UNCD film annealed at 1000 °C. In this case, a novel conduction mechanism that O +-implanted nano-sized diamond grains supply n-type conductivity and the amorphous carbon grain boundaries give a current path to the UNCD films is proposed. © 2011 American Institute of Physics.

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