Surface characterization of Cu/Ti thin films by fractal analysis

Copper/Titanium (Cu/Ti) metallic thin bilayer films, xCu/10nmTi/Si and xCu/30nmTi/Si (x=10nm, 20nm, 30nm, respectively), were deposited by DC magnetron sputtering technique. An atomic force microscopy (AFM) was used to measure the surface morphology. The height-height correlation function, described by the surface parameter of roughness exponent α, together with the evolutions of the familiar parameters of roughness w and autocorrelation length ξ, was used to describe the surface quantitatively. The fractal dimension D_f of the surface was calculated. The values of D_f reduce with the Cu film thickness increasing for the samples of Cu/10nmTi/Si and increase for the samples of Cu/30nmTi/Si. The surface will be rougher for the samples of Cu/10nmTi/Si as the Cu film increasing from 10nm to 30nm and become smoother for the samples of Cu/10nmTi/Si.