Nanoscale Quantum Physics Group
Research - Project Three
Pinhole formation in a solid phase epitaxial film of CoSi2
The long-standing pinhole problem in solid phase epitaxial growth of a CoSi2 film on Si(111) has
been revisited with in situ scanning tunneling microscopy. While the as-deposited film with 5 Å of CO at room
temperature shows a smooth granular texture with original substrate terraces remaining intact, annealing at
580o C produces an epitaxail CoSi2 film with large pinholes enclosed by a thin ring of
CoSi2, exhibiting a volcano feature. Quantitative analysis shows that the formation of pinholes is a
result of rapid Si outward diffusion from bulk to surface, and of the subsequent Si reaction with Co on the outer
surface. Evidence suggests that inhibiting the Si diffusion channels during the thermal annealing process is the
key to solving the pinhole problem.
For a detailed description see: Ruan, L., Chen, D.M. Appl. Phys.
Lett. 72, 3464-3466 (1998) and the online poster .
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