  A 30 nm Pt thin film evaporated onto a Si wafer was sputtered by 8 keV
Ar$^{+}$ ions at various ion doses. The evolution of the modified sputtered
films was monitored by atomic force microscopy (AFM), high resolution scanning
electron microscopy (HRSEM) and Rutherford backscattering spectrometry (RBS).
The most interesting observation was the formation of mound-like structures on
the metal surface. Morphological data were quantitatively analysed within the
framework of the dynamic scaling theory. Analyses of the height-height
correlation function for different doses yield roughness exponents $\alpha $ in
the range 0.65 - 0.87, while the root-mean-square roughness amplitude $w$
evolves with the dose $\phi $ as a power law $w\propto \phi ^{\beta}$, with the
growth exponent, $\beta $ $\approx $ 0.3. The results are discussed.
