Cathodoluminescence of rare earth implanted Ga₂O₃and GeO₂nanostructures

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(2)O(3) and GeO(2) structures implanted with Eu show the characteristic red luminescence peak centered at around 610 nm, due to the (5)D(0)-(7)F(2) Eu(3+) intraionic transition. Sharpening of the luminescence peaks after thermal annealing is observed in Eu implanted β-Ga(2)O(3), which is assigned to the lattice recovery. Gd(3+) as-implanted samples do not show rare earth related luminescence. After annealing, optical activation of Gd(3+) is obtained in both matrices and a sharp ultraviolet peak centered at around 315 nm, associated with the Gd(3+) (6)P(7/2)-(8)S(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.

Nanostructures and thin films of transparent conductive oxides studied by perturbed angular correlations

“…Thus, in this study, thin films of ZnO and Cd x Zn 1 x O (x = 0.16) were investigated. Gallium oxide (Ga 2 O 3 ) has the biggest band-gap among the transparent conductive oxides, 4.8 eV , making it interesting for photonics working in the UV and visible wavelength region [3,[10][11][12][13]. However, as in the case of ZnO, it is an intrinsic n-type semiconductor and it has been proven very difficult to obtain p-type doping, which is fundamental for technological applications.…”

“…However, as in the case of ZnO, it is an intrinsic n-type semiconductor and it has been proven very difficult to obtain p-type doping, which is fundamental for technological applications. Nonetheless, its nanowires could be used as effective waveguides and optical doping using rare earth ions in-situ or by ion implantation has been demonstrated [3,13]. In this work we study the viability of ion implantation to incorporate dopants into these nanowires.…”

“…Two different samples of -Ga 2 O 3 were used, a powder pellet and nanowires (both polycrystalline-like, consisting of a distribution of randomly oriented micro-crystals, from the point of view of the PAC measurement). The nanowires were grown from metallic gallium in a tube furnace using a vapour-solid growth mechanism reported elsewhere [3]. The grain size of the pellet was in the range of several microns whereas the nanowires' length and thickness was up to tens of microns and between tens to hundreds of nanometers, respectively.…”

“…PAC probes the charge density distribution in the surroundings of chosen radioactive nuclei, thus allowing characterizing the probe's real environment at the atomic scale. We have chosen to study ZnO and Cd x Zn 1 x O thin films -aimed to cover luminescence wavelengths from UV to yellow [2] -and the technologically relevant high -K factor Ga 2 O 3 nanostructures and Ga 2 O 3 pellets [3]. Both materials belong to the family of transparent conductive oxides and the used PAC probe, 111m Cd/ 111 Cd, is well suited to study the microscopic physical properties of these materials being an isoelectronic impurity in the case of ZnO and a possible ptype dopant in the case of Ga 2 O 3 .…”

Tailoring the shape of oxide complex nanostructures

“…We have successfully fabricated several oxide nanowires by simple evaporation-solidification mechanism [4][5][6][7][8] . The key parameters that control the growth process are the temperature, the duration, the gas flow and the source materials.…”