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Surface roughness mediated specularity parameter of thin Cu films

APL (Applied Physics Letters)

Roughness induced resistivity variation of thin metal lms is conveniently described by the Fuchs-Sondheimer
(FS) model, where the phenomenological specularity parameter p is used to quantify the extent of specular
scattering at a surface. However, p is a lumped parameter and does not include microscopic information that
characterize roughness viz. auto-correlation function, root mean square (RMS) height and correlations length.
In this work, we extract these roughness parameters for Cu lms of thickness ranging from 31 nm to 95 nm. We
found that the roughness-roughness correlation function is exponential with a characteristic correlation length
which monotonically increases with lm thickness. Using this we predict roughness parameter dependent
specularity coecient, which has an implicit thickness dependency. This alters the resistivity scaling compared
to the prevailing model of resistivity scaling where p is assumed to be constant.

Appl. Phys. Lett. 118, 133504 (2021)