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.

Tuneable Nanostructuring of Highly Transparent Zinc Gallogermanate Glasses and Glass‐Ceramics

“…This trend has been also observed in germanate-based materials for which the authors have shown by optical absorption measurements that Ni ions are fully embedded in the crystalline phase. [ 53 ] No emission in the near-infrared could be obtained in our glass material, even for a 980 nm excitation, as previously reported for several glass systems. [ 48,54,55 ] In the glass ceramic, the emission observed at around 1300 nm for a similar excitation corresponds to octahedral coordinated Ni 2+ ions ( 3 T 2 → 3 A 2 transition).…”

“…[ 48,54,55 ] In the glass ceramic, the emission observed at around 1300 nm for a similar excitation corresponds to octahedral coordinated Ni 2+ ions ( 3 T 2 → 3 A 2 transition). [53][54][55] The Ni 2+ luminescence emission around 1300 nm in the octahedral site has already been reported. [ 48,54,55 ] In Figure 4 b, the emission maximum is located at 1325 nm.…”

Light-emitting Ga-oxide nanocrystals in glass: a new paradigm for low-cost and robust UV-to-visible solar-blind converters and UV emitters

“…Particularly, no data are available on the intrinsic properties of g-Ga 2 O 3 NCs in glass, since the only studies on embedded variants were essentially aimed at obtaining convenient hosts for IR-emitting ions, such as Ni 2+ and Cr 4+ . 15,17,34 As a result, the data in Fig. 2 constitute the rst quantitative insight into the absorption edge of g-Ga 2 O 3 as a nanophase in a solid matrix.…”

“…Doping the investigated glass with Ni 2+ ions gives rise, in fact, to full incorporation of Ni 2+ into g-Ga 2 O 3 NCs upon nanocrystallization, as we found in a previous work by registering the changes of Ni 2+ crystal eld absorption and IR luminescence. 15 The selective doping of NCs with Ni 2+ ions gives a tool for lowering N A by means of heterovalent cations with oxidation state smaller than Ga 3+ . Bearing in mind that acceptors consist of (V O , V Ga ) 0 complexes -and that the presence of native V Ga is somewhat related to the oxygen deciency determined by the synthesis conditions -we expect that Ni 2+ ions could lower the number of Ga 3+ vacancies required by charge neutrality at a xed oxygen defectiveness.…”

“…[15][16][17] At present, however, data on light emission properties of nanosized Ga oxides are only available for nanopowders and nanowires, or NCs in colloidal solutions. 14,[18][19][20][21][22][23][24][25] A large fraction of those results regard the b-Ga 2 O 3 phase, 4,6,7,[10][11][12][13][14]22 whereas only a few studies concern the metastable polymorph g-Ga 2 O 3 .…”