|
We study the effect of Ar+ irradiation during the growth of BN and a-C by sputter
deposition. We found that the dominant effects for the BN growth are the
subplantation of N+ and B+ species. For energies higher than the threshold for Ar+
subplantation, the Ar+ penetrate into BN and disrupts the B-N bonds resulting to
defective BN. The existence of Ar impurities in such films promotes the stability of
C impurities. These effects result to a very narrow window of ion energy (<40 eV)
were successful growth of BN films may be achieved. On the other hand, in a-C films
sp3-bonded C we found a close correlation between the Ar impurities with the sp3 C-C
bonds, which suggest that Ar impurities promote the formation of sp3-bonded carbon
in a-C, in contrast to BN growth. In addition, it was found that the films grown
using C+ (Ar+) exhibit a sp2 (sp3) surface, while the deeper monolayers are sp3
(mixed sp3-sp2) bonded. We found two mechanisms of sp3 formation: on the surface and
in the bulk of a-C. We conclude that at medium energy (>100 eV) the surface effects
are negligible (for both C+ and Ar+), while the surface processes dominate when
low-energy (~40 eV) Ar+ ions are used.
|