Structural and optical properties of GaAs quantum dots formed in SiO2 matrix

A shallow sequential ion implantation of As and Ga ions into pure silica substrates was conducted to form GaAs quantum dots near the substrate surface. The main efforts were made to understand how the post thermal annealing affects the formation, thermal stability, and chemical composition of nanoparticles in a silica host. When the sample was annealed at 600 °C under 96% Ar + 4% H2, X-ray diffraction (XRD), infrared reflectance (IR reflectance), and tunneling electron microscopy (TEM) confirmed the formation of GaAs quantum dots near the silica surface. X-ray photoemission spectroscopy (XPS) showed 3d electron binding energies of Ga and As at 18.8 eV and 40.75 eV suggesting GaAs nanocrystal formation. An additional band was also observed at ∼ 20.12 eV which was attributed to the presence of GaOx. At 1000 °C, however, an additional peak is also observed near 44.1 eV indicating As2O3 formation. It was argued that the formation of GaOx at 600 °C and As2O3 at 1000 °C was primarily due to the volatile nature of the Ga and its related compounds. High resolution Rutherford back scattering (RBS) using 14N3+ ions showed that 1000 °C annealing resulted in 50% loss of Ga and a 35% position shift toward the surface while As concentration is unchanged with a 25% position shift toward the surface.