Microstructural evolution of ultrathin amorphous silicon films by real-time spectroscopic ellipsometry

Abstract
The nucleation of thin-film amorphous silicon (a-Si), sputter deposited on oxidized c-Si, is investigated by real-time spectroscopic ellipsometry from 1.5 to 4.5 eV with a resolution of 3 s and a repetition period of 15 s. Analysis of real-time spectra provides unprecedented sensitivity and quantitative information on the microstructural evolution. Under preparation conditions resulting in a-Si of the highest bulk Si-Si bond-packing density, an abrupt transition representing the onset of bulk film growth can be identified unambiguously when nuclei reach a thickness of 13±1 Å.