IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Surface Engineering Tuesday Sessions
       Session SE-TuA

Paper SE-TuA7
Ion-bombardment Induced Phase Transformation of Cubic Boron Nitride Studied by Reflection Electron Energy Loss Spectroscopy

Tuesday, October 30, 2001, 4:00 pm, Room 132

Session: Hard and Superhard Coatings
Presenter: Y.Y. Hui, Chinese University of Hong Kong, P.R. China
Authors: Y.Y. Hui, Chinese University of Hong Kong, P.R. China
K.W. Wong, Chinese University of Hong Kong, P.R. China
W.M. Lau, Chinese University of Hong Kong, P.R. China
Correspondent: Click to Email
The phase transformation of cubic boron nitride (c-BN) in the near surface region of a c-BN (111) facet induced by low energy argon ion bombardment has been investigated by reflection electron energy loss spectroscopy (REELS), with the objective of tracking possible growth mechanisms of c-BN in ion assisted vapor deposition. By removing Tougaard background of the REELS spectra, we can quantitatively measure the percentage of different BN phases on c-BN surface after ion bombardment. In addition, varying the energy of the incident electron beam from 250 eV to 650 eV allowed the adjustment of sampling depth of a c-BN surface from 14 Å to 27 Å. It was found that with an ion energy of 500 eV at a fluence of 5 x 10@super 16@ ions/cm@super 2@, 76 % of c-BN was found transformed to h-BN and a-BN in a top surface layer of 8 Å. Lowering down the argon bombardment energy to 200 eV reduced the defective layer thickness to 5 Å. A damage saturation was observed at a fluence of 6 x 10@super 16@ ions/cm@super 2@, at which about 10% of c-BN was transformed into non-cubic phases. Through further investigations on the damage saturation at other ion energies, the effects of ion beam bombardment on a c-BN surface was comprehensively studied. The present work gives, for the first time, a quantitative explanation of the difficulty in growing pure c-BN films with ion assisted deposition and the presence of an upper-bound in ion energy above which h-BN and a-BN are generated.