Synthesis, luminescence and micro-Raman study of In₂Ge₂O₇ nanobelts and nanowires

Highlights: • Luminescence of indium germanate nanostructures grown by VS has been investigated. • Measurements show complex emission bands with several components at 2.4 eV and 3.28 eV. • Some emissions are related to Ge–O features and not to the suggested In–O groups. • Micro-Raman spectra have peaks different from those of germanium or indium oxide. • First results on the waveguiding behaviour of In₂Ge₂O₇ wires are also reported. - Abstract: Indium germanate (In₂Ge₂O₇) nanobelts and nano- and microwires have been synthesized by a thermal evaporation–deposition method and their luminescence properties have been investigated. High-resolution transmission electron microscopy shows the growth direction of the nanobelts. Cathodoluminescence in the scanning electron microscope and photoluminescence show the existence of a broad complex emission band with several components in the range 1.70–2.80 eV and a band at 3.20–3.30 eV. Comparison of the observed luminescence with the luminescence of GeO₂ suggests that some of the components are related to the presence of Ge₂O₇ groups in the germanate crystal structure and not to the sheets of InO₆ octahedra of the structure. Waveguiding behaviour of In₂Ge₂O₇ nano- and microwires has been demonstrated under excitation with 325 nm light. Raman spectra of the nanobelts have characteristic peaks which could enable to correlate specific Raman features with the presence of In₂Ge₂O₇ and to use this technique for indium germanate assessment