Dynamic scaling in ion etching of tungsten films

Grazing incidence x-ray scattering is employed in situ and in real time to investigate quantitatively the time-dependent roughening of an ion bombarded tungsten layer. The evolution of surface morphology is analyzed in terms of power spectral density functions extracted directly from the measured scattering diagrams. In the [1×10−4,4.6×10−2]nm−1 spatial frequency range, roughness spectra for progressive thickness are shown to obey a universal scaling form leading to scaling exponents consistent with the prediction of the Kardar-Parisi-Zhang equation in 2+1 dimensions.