In situ low-angle x-ray scattering study of phase separation in initially mixed HfO2–SiO2 thin film interfaces

In this letter, we report on phase separation kinetics at initially mixed interfaces of HfO2–SiO2 multilayers measured by low-angle x-ray scattering. Multilayers were fabricated by sputtering and ultraviolet ozone oxidation of ultrathin Hf and Si precursor films. The multilayers were subjected to isothermal anneals in the temperature range 680–762 °C during in situ x-ray scattering measurements. The evolution of the intensity of the multilayer x-ray satellite peaks, the Fourier components of the composition modulation, were consistent with diffusional phase separation of HfO2 and SiO2 during the anneals. The effective interdiffusivity D̃L of the HfO2–SiO2 alloy present at the interfaces in the as-deposited multilayers was estimated from the measured intensity change of the first-order satellite reflection as a function of annealing time. The extracted activation energy for the phase separation process was 2.06±0.15eV for the multilayer samples studied.