Ion implantation and cluster formation in silica

Abstract

Cathodoluminescence (CL), scanning transmission electron microscopy (STEM), and energy dispersive X-ray analysis (EDX) have been used to investigate Si and Ge cluster formation in amorphous silicon dioxide layers and their respective luminescence behavior. Commonly, CL emission spectra of pure SiO 2 are identified with particular defect centers within the atomic network of silica including the non-bridging oxygen-hole center (NBOHC) associated with the red luminescence (R) at 650 nm (1.9 eV) and the oxygen deficient centers (ODC) with the blue (B) (460 nm; 2.7 eV) and ultraviolet UV (295 nm; 4.2 eV) bands. In Ge + ion implanted SiO 2 an additional violet (V) Ge related emission band is identified at (410 nm; 3.1 eV). A post-implantation thermal annealing at temperatures T a = 700 –1100 ∘C in dry nitrogen leads up to 900 ∘C to a huge increase of the violet luminescence, followed by a decrease towards 1100 ∘C. The strong increase of the violet luminescence is associated with formation of low-dimension Ge aggregates like dimers, trimers and higher formations; the following decay of luminescence is due to further growing to Ge nanoclusters.