Real-time X-ray studies of fundamental surface growth processes
Rainville, Meliha Gozde
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In this research, some fundamental aspects of surface growth processes are investigated through in-situ synchrotron based x-ray techniques, including a new coherent x-ray technique developed as part of this work, as well as ex-situ Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and simulation. The first part of this dissertation focuses on careful examination of early-time kinetics of indium (In) island growth via real-time Grazing Incidence Small Angle X-ray Scattering (GISAXS) since it is a good example of simple growth systems allowing the results to be directly compared to surface growth theories and also because of its technical relevance for III–V semiconductor deposition. The results are compared with Family-Meakin (FM) droplet growth and coalescence theory through Monte Carlo simulations. In addition, room temperature deposition of amorphous silicon (a-Si) through DC magnetron sputtering onto a silicon (Si) substrate has been investigated via real-time GISAXS. The deposition conditions are optimized to create an idealized growth environment so that the results can be directly compared to surface growth models. Performing the deposition at room temperature results in adatoms having limited surface mobility, which causes formation of correlated mound-like structures on the surface at the early stages of the growth. The correlation distance between the mount-like structures is found to grow linearly with time. The results are compared to a ballistic deposition model including self-shadowing and desorption effects. The second half of this study focuses on investigation of the kinetic roughening dynamics of thin film growth, where the local dynamics are measured after the overall kinetic evolution of the surface roughness reach a steady-state saturation. Coherent X-ray GISAXS (Co-GISAXS) has been developed as a new approach to investigate surface dynamics during thin film deposition. Room temperature deposition of a-Si and amorphous tungsten disilicide (a-WSi2) through DC magnetron sputtering onto respectively Si and SiO2 substrates has been examined. The overall dynamics are complex, but power law behavior is observed for the structure factor and correlation times at the most surface sensitive section of the data. This research demonstrated that Co-GISAXS is a powerful new approach to investigate the correlated dynamics between surface and sub-surface structures.