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Abstract:
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This dissertation determined how the electronic and atomic structure of Ni/Cu(100) and
Co/Ru(0001) thin films affect C6O-metal bonding and local magnetic properties at the
surface. In-situ spin-averaged and spin-polarized scanning tunneling microscopy and
spectroscopy techniques were used in this study. Homoepitaxial growth studies of
Ni(100) and Co(0001) films investigated the influence of C60 on film growth. On 7.6 ML
Ni films, C60 showed no obvious effect on the continued crystalline growth of Ni. The low
mobility of C60 on the Ni surface and high Ni diffusion barrier limited the occurrence of
Ni-C60 collisions during growth. On 1.84 ML Co films, crystalline growth with moire
reconstructions continued with CGO present at the surface. However, Co islands were
observed only nucleating and growing from step edges and around C60 suggesting the
Co-C6O bond is stronger than the Co-Co bond on Co terraces. C60 mobility was also
observed to vary across the Co film surface due to local variations in film reconstruction
and dislocation networks. The results show that the nature of the C60-metallic bond at
the surface can effect film growth and morphology.
Scanning tunneling spectroscopy (STS) studies suggest that the spin-averaged and spinpolarized
Co(0001) electronic structure is influenced by a number of factors: (i)
sequential layer stacking (fcc/hcp), (ii) strain-induced reconstruction (moire), (iii) Co film
thickness, and (iv) dislocations and defects at the surface. Spin-polarized STS
measurements resolved spectral contributions from Co layer stacking and opposite
perpendicular magnetic spin-orientations. The magnetic domain regions identified were
fcctt/fcet..J, and hcptt/hcpt..J, stacked domains, respectively. No evidence of an in-plane
magnetic spin-orientation or spin re-orientation transition was observed at the Co
surface; however magnetic domain walls showed evidence of pinning at dislocation
lines. Spin-polarized STM/STS measurements did not reveal any affect of C60 on the
local magnetic properties of Co. However, an internal structure of C60 molecules
adsorbed on the Co(0001) film surface was observed, corresponding to a 3-fold
(symmetry) molecular-orientation; and in the near-region where CGO clusters were
adsorbed, Co surface state peaks were observed to be absent, suggesting the local
electronic structure of Co is perturbed by the presence of C60• |
