Colloidally stable germanium nanocrystals for photonic applications.

We report the development of a straightforward synthesis for colloidally stable germanium nanocrystals for use as a solution-processable precursor for the bottom-up fabrication of functional thin films. SiO(2)-embedded germanium nanocrystals are produced by the reductive thermal processing of sol-gel glasses derived from mixtures of tetraethoxyorthogermanate (TEOG) and tetraethoxyorthosilicate (TEOS), and free-standing germanium nanocrystals are liberated from the encapsulating silicon dioxide through sequential chemical etching. The applicability of these germanium nanocrystals as a solution-processable thin film precursor is demonstrated by the fabrication of high refractive index thin films.