Synthesis, properties and applications of germanium nanocrystals

We present an overview of the synthesis, properties and applications of germanium (Ge) nanocrsytals, referring to our recent review article published in Encyclopedia of Nanoscience and Nanotechnology [1]. We developed two fabrication techniques; the cluster-beam evaporation and the gas evaporation with a supersonic jet nozzle, to obtain smaller Ge nanocrystals with a good size distribution and observed unique optical and electrical phenomena such as photooxidation, blue-light emission, coulomb blockade. and phase-transformation. Although light-emitting devices may be the first choice among the device applications of Ge nanocrystals similar to Si nanocrystals, the short-term development of such devices is hindered by a low luminescence efficiency and the broad peak of the luminescence spectra. A new application that makes the best use of the properties of Ge nanocrystals and that cannot be realized with any other material must be explored for Ge nanocrystals to become more industrially important.