Synthesis of germanium nanocrystals in hafnium aluminum oxide matrix

An examination on the effect of annealing temperature and duration, and the germanium (Ge) concentration on the growth of Ge nanocrystals in hafnium aluminum oxide (HfAlO) matrix, was carried out using a combination of Raman spectroscopy, transmission electron microscopy, and secondary ions mass spectrometry techniques. We found Ge nanocrystals in the HfAlO matrix with a Ge content of 10.5 at. % when annealed at 800 degrees C. At a relatively higher content of Ge at 23.3 at. % in HfAlO film, a significant outdiffusion of Ge at the film surface or diffusion into the Si substrate occurred, and this imposes a narrow annealing condition for the formation of nanocrystals. We attribute the different nanocrystal formation characteristics in the HfAlO and silicon oxide matrices to the difference crystallization temperatures of HfAlO and silicon oxide films. (c) 2007 American Institute of Physics.