title: Nickel-assisted growth and selective doping of spinel-like gallium oxide nanocrystals in germano-silicate glasses for infrared broadband light emission.
abstract: The target of taking advantage of the near-infrared light-emission properties of nickel ions in crystals for the design of novel broadband optical amplifiers requires the identification of suitable nanostructured glasses able to embed Ni-doped nanocrystals and to preserve the workability of a glass. Here we show that Ni doping of Li(2)O-Na(2)O-Ga(2)O(3)-GeO(2)-SiO(2) glass (with composition 7.5:2.5:20:35:35 and melting temperature 1480 °C, sensibly lower than in Ge-free silicates) enables the selective embedding of nickel ions in thermally grown nanocrystals of spinel-like gallium oxide. The analysis of transmission electron microscopy and x-ray diffraction data as a function of Ni-content (from 0.01 to 1 mol%) indicates that Ni ions promote the nanophase crystallization without affecting nanoparticle size (~6 nm) and concentration (~4 × 10(18) cm(-3)). Importantly, as shown by optical absorption spectra, all nickel ions enter into the nanophase, with a number of ions per nanocrystal that depends on the nanocrystal concentration and ranges from 1 to 10(2). Photoluminescence data indicate that fast non-radiative decay processes become relevant only at mean ion-ion distances shorter than 1.4 nm, which enables the incorporation of a few Ni ions per nanoparticle without too large a worsening of the light-emission efficiency. Indeed, at 0.1 mol% nickel, the room temperature quantum yield is 9%, with an effective bandwidth of 320 nm.
authors.affiliation: International Laboratory of Glass-Based Functional Materials, Mendeleev University of Chemical Technology of Russia, Moscow, Russia.
authors.forename: V N
authors.initials: VN
authors.lastname: Sigaev
authors.forename: N V
authors.initials: NV
authors.lastname: Golubev
authors.forename: E S
authors.initials: ES
authors.lastname: Ignat'eva
authors.forename: V I
authors.initials: VI
authors.lastname: Savinkov
authors.forename: M
authors.initials: M
authors.lastname: Campione
authors.forename: R
authors.initials: R
authors.lastname: Lorenzi
authors.forename: F
authors.initials: F
authors.lastname: Meinardi
authors.forename: A
authors.initials: A
authors.lastname: Paleari