Characterization of multiscale surface evolution of polycrystalline copper thin films.

Surface morphologies of Cu films with different thicknesses varying from 110 to 660 nm deposited on Ta-covered Si(111) substrates at 700 K by magnetron sputtering were investigated by atomic force microscopy (AFM). The global surface fluctuation image of the film was obtained directly from AFM measurement with larger scan size. Multiresolution wavelet transform approach incorporating power spectrum density analysis was proposed to extract the local surface fluctuation image. From these images, the dynamical exponents of both global and local surface fluctuations were calculated in terms of dynamic scaling theory. The multiscale surface evolution of Cu film could be characterized by a set of local exponent values αl≈0.87 and βl≈0.22, and global exponent values αg≈0.83 and βg≈0.85. The dynamic evolution of local surface fluctuations is consistent well with that predicted by linear surface diffusion-dominated growth equation, while the dynamic evolution of global surface fluctuations exhibits anomalous scaling behavior due to the presence of nonlocal bulk diffusion. [ABSTRACT FROM AUTHOR]