STUDIES ON ROOM-TEMPERATURE CHARACTERISTICS AND MECHANISM OF VISIBLE LUMINESCENCE OF GE-SIO2 THIN-FILMS

Photoluminescence (PL) characteristics of Ge nanocrystallites of diffe rent grain sizes embedded in SiO2 thin films prepared by the ion-beam sputtering technique have been further studied at room temperature und er different exciting radiations. The dominant fluorescent band, with a peak at similar to 420 nm under the exciting radiation of lambda=300 nm, and two new luminescence peaks at about 420 and 470 nm under lamb da=633 nm radiation are observed in the wavelength region of 380-520 n m for the first time. Results indicate that the PL intensity depends o n the size of the Ge nanocrystallites, but the position of the PL peak s is not closely related to the size of the Ge nanocrystallites. It is suggested that the mechanism of the visible PL can be discussed by a quantum size effect which is also related to the new microstructure of the embedded Ge nanocrystallites. (C) 1997 American Institute of Phys ics.