Visualizing the evolution of surface morphology and surface bond strain during plasma deposition of amorphous silicon thin films

Fundamental understanding of atomic-scale processes that determine the surface morphology of hydrogenated amorphous silicon (a-Si:H) thin films during plasma deposition is essential to develop systematic strategies for depositing smooth device-quality a-Si:H films. We have developed visualization tools for monitoring the evolution of surface morphology, atomic coordination, and bond strain distribution during radical precursor migration on a-Si:H surfaces; these tools are used here to study the mechanisms of SiH₃ diffusion on the a-Si:H surface and elucidate valley-filling phenomena leading to smooth a-Si:H films. We present surface characterization results during a radical migration trajectory representative of the early stage of plasma deposition: the SiH₃ precursor is impinged on a hill and migrates until it is incorporated into a nearby valley on the a-Si:H surface.