Synthesis and optical properties of Zn2GeO4 microrods

Abstract Zinc germanate (Zn 2 GeO 4 ) microrods have been grown by a catalyst free thermal evaporation-deposition method. The microrods, with lengths of up to hundreds of microns have hexagonal cross section and faceted tips with morphologies in agreement with the rombohedral crystal structure of the germanate. Photoluminescence (PL) of the structures shows a broad band centered at about 2.4 eV, which is found by Gaussian deconvolution to consist of three components. A luminescence band at higher energies, centered at about 3.45 eV, is revealed by excitation with 20 kV electrons in the scanning electron microscope (SEM) or by PL under high excitation conditions. Resonance peaks observed in the luminescence spectra have been interpreted by the formation of Fabry–Perot modes in the hexagonal cross section of the rods. The waveguiding behavior of the rods has been assessed by excitation with a 325 nm laser and by detection of the excited luminescence emission transmitted along the rod. Micro Raman spectra of the rods show four bands in the range 740 cm −1 –820 cm −1 , with the most intense one peaked at 801 cm −1 . Comparison with Raman spectra of GeO 2 and of other germanates suggests that this set of bands, characteristic of Zn 2 GeO 4 is related to vibrations of Ge–O bonds.