Structural and optical study of Ge nanocrystals embedded in Si3N4 matrix

Ge nanocrystals were fabricated in Si3N4 matrix by rf (radio frequency) magnetron sputtering, followed by post-annealing in a conventional tube furnace filled with N2. Ge content was varied between 30-50vol% in Ge-rich silicon nitride (GRN) layer with variation of annealing temperature between 600-900 °C were applied to study the crystallization properties. The structure of the Ge nanocrystals was studied by Raman spectroscopy, glancing incidence x-ray diffraction (GIXRD) and transmission electron microscope (TEM). The composition and bonding status of Ge nanocrystals was confirmed by x-ray photoelectron spectroscopy (XPS). TEM images, Raman and XRD results show that the crystallization transition is dependent on temperature and Ge content. Crystals in 50vol% annealed at 900 °C were found as partially oxidized with 2at% of oxygen during the annealing process. This was shown by the XPS result. However, absorption measurement did not show evidence of quantum confinement of the Ge crystals.