GeO_2 Nanowires Doped with Optically Active Ions

Abstract

GeO_2 nanowires doped with Eu, Er, or Mn, as well as codoped with each of these ions and Sri, have been grown by a catalyst-free vapor-solid process. The incorporation of Sri has been found, in all cases, to favor the formation of straight wires, which make them more appropriate for waveguiding purposes. Cathodoluminescence (CL.) in the scanning electron microscope (SEM) has been used to investigate the complex light emission from the nanowires. Rare earth ion emission lines and defect related bands have been observed in Eu- and Er-doped nanowires. Optical coupling and waveguiding behavior of Er-doped GeO_2 nanowires have been demonstrated for green laser light and for Er excited luminescence in the wires. In Mn-doped GeO_2 nanowires a band centered at 1.75 eV had been detected. X-ray photoemission measurements show the presence of GeO oxide in the surface of the GeO_2 wires, which influences their native defect structure.