Thin Film Growth: Exploring Nanoscale Local Dynamics versus Average Kinetics*

We have studied the average kinetics and real-time dynamics during amorphous WSi₂ film growth as a function of pressure by means of X-ray photon correlation spectroscopy (XPCS). It's known that, as a consequence of kinetic behavior, there is a transition from smooth to rough growth surfaces with increasing pressure. It's observed that the speckle-averaged X-ray scattering intensity doesn't change after the film reaches a kinetic steady-state. Timescale parameters were determined for each pressure condition. Peaks found in intensity vs. time curves characterize the time when the local roughness is maximum at the length scale 2π/q_//. Dynamic behavior is analyzed by means of two-time correlation functions and g₂ functions. The timescales for reaching dynamic and kinetic steady states, and the correlation time of surface structure in the final dynamic steady state all decrease as growth pressure and final surface roughness increase. In high q_// regions, an average local structure may be stabilized while deposition, relaxation and coarsening in nanoscale have not yet reached a dynamic equilibrium.