Low energy Ar⁺ ion beam induced kinetic roughening of thin Pt films on a Si substrate

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.