Luminescence study of Si ^- and Ge ^- implanted (1̄102) sapphires

Implantation with 30 keV Si ^- or Ge ^- and subsequent annealing at 1100°C create nanocrystalline Si or Ge (nc-Si or nc-Ge) in host materials such as (1̄102) sapphire and fused silica. Photoluminescence (PL) and cathodluminescence (CL) have been used to investigate luminescence properties of nc-Si or nc-Ge embedded in the host materials. Light emissions from Si ^-- or Ge ^-- implanted samples are compared with those from O ^-- and Al ^-- implanted ones in order to investigate whether they are from nc-Si (or nc-Ge) or defect-related. The CL band at 574 nm and the PL band at 1380 nm are interpreted as Si- and Ge-nanocrystal-related, respectively, and the CL bands at 328 and 411 nm as defect-related. Especially, the 411-nm band is found after annealing as well as before annealing and sharply increases on increasing the implant dose. This indicates that even high-temperature annealing cannot completely rule out implantation-induced defect luminescence.