Light-emitting Si nanostructures formed in SiO2 on irradiation with swift heavy ions

SiO2 layers containing implanted excess Si are irradiated with Xe ions with an energy of 130 MeV and doses of 3 x 1012-1014 cm-2. In the samples irradiated with a dose of 3 x 1012 cm-2, ∼1012 cm-2 segregated clusters 3-4 nm in dimension are detected by transmission electron microscopy. With increasing dose, the dimensions and number of these clusters increase. In the photoluminescence spectrum, a 660- to 680-nm band is observed, with the intensity dependent on the dose. After passivation of the sample with hydrogen at 500 deg. C, the band disappears, but a new ∼780-nm band typical of Si nanocrystals becomes evident. On the basis of the entire set of data, it is concluded that the 660- to 680-nm band is associated with imperfect Si nanocrystals grown in the tracks of Xe ions due to high ionization losses. The nonmonotonic dependence of the photoluminescence intensity on the dose is attributed to the difference between the diameters of tracks and the diameters of the displacements' cascades responsible for defect formation.