Cathodoluminescence of rare earth implanted Ga_2O_3 and GeO_2 nanostructures

Abstract

Rare earth (RE) doped gallium oxide and germanium oxide micro- and nanostructures, mostly nanowires, have been obtained and their morphological and optical properties have been characterized. Undoped oxide micro- and nanostructures were grown by a thermal evaporation method and were subsequently doped with gadolinium or europium ions by ion implantation. No significant changes in the morphologies of the nanostructures were observed after ion implantation and thermal annealing. The luminescence emission properties have been studied with cathodoluminescence (CL) in a scanning electron microscope (SEM). Both β-Ga_2O_3 and GeO_2 structures implanted with Eu show the characteristic red luminescence peak centered at around 610 nm, due to the 5ˆD0–7ˆF_2Euˆ3+ intraionic transition. Sharpening of the luminescence peaks after thermal annealing is observed in Eu implanted β-Ga_2O_3, which is assigned to the lattice recovery. Gd3+ as-implanted samples do not show rare earth related luminescence. After annealing, optical activation of Gdˆ3+ is obtained in both matrices and a sharp ultraviolet peak centered at around 315 nm, associated with the Gdˆ3+ 6P_7/2–8ˆS_7/2 intraionic transition, is observed. The influence of the Gd ion implantation and the annealing temperature on the gallium oxide broad intrinsic defect band has been analyzed.