Atomic migration of silicon through grain boundaries of a thin polycrystalline Cu
film and island
formation on the Cu surface were studied in the temperature range of 403–520 K. Samples
used in
these experiments was prepared on Si(111) wafers by room temperature magnetron sputtering
and they consisted of amorphous Si layer (80 nm) and polycrystalline Cu layer (40
nm). The
silicon layer served as the source layer of diffusion, while the copper surface was
the accumulation surface. Detection of Si atoms on the accumulation surface after
penetration through the Cu
layer was made by low energy ion scattering spectroscopy and the grain boundary diffusion
coefficient DGB was determined from the appearance time. The depth distribution of
Si in the Cu
film was analysed by secondary neutral mass spectroscopy. From this depth distribution,
DGB was
also determined. By scanning probe microscope and electron microscope measurements,
it was
experimentally detected that Si atoms on the Cu surface did not form a continuous
layer. Instead,
amorphous Si islands were formed at the accumulation surface with surface protrusions
in their
centres.
