Stable blue photoluminescence (PL) at 580 nm visible to the naked eye has been observed for the samples consisting of Ge nanocrystals (nc‐Ge) embedded in a silicon oxide (SiO2) solid matrix, fabricated by atmospheric pressure chemical vapor deposition techniques. Raman spectroscopy measurement strongly suggests the existence of Ge nanocrystal in the SiO2matrices. The size of nc‐Ge is dependent on aftergrowth thermal treatment under nitrogen ambient, and it is found that temperature above 700 °C for 1 h only exhibits the PL peak at the visible wavelength. The samples annealed for longer times at 700 °C do not exhibit any PL peak which is correlated with the change of the nanocrystal size. ©1996 American Institute of Physics.