Synthesis of Germanium Dioxide Microclusters on Silicon Substrate in Non-aqueous Solution by Electrochemical Deposition

<p>We report the formation of crystalline germanium dioxide (GeO₂) microclusters on n-Si (100) electrodeposited in non-aqueous electrolyte (a mixture of 5 vol.% germanium tetrachloride (GeCl₄) and dipropylene glycol (C₆H₁₄O₃) ) at current density of 20 mA/cm² for 200 sec. Pt, C and Ge are used as an anode while Si acts as a cathode. Field- emission scanning electron microscopy (FESEM) images show that the deposited GeO₂ microclusters are having rounded-mushroom-shaped particles with the smallest size of 660 nm. Energy dispersive x-ray (EDX) spectra reveal that the particles are only composed of Ge and O elements. Raman spectra confirm the formation of crystalline GeO₂ with trigonal bonding structures in all samples. The photoluminescence (PL) spectra show two significant emission peaks in visible range at 2.27 eV and 2.96 eV, which seems to be attributed by GeO₂ and Si defects. C₆H₁₄O₃seems to contribute to the formation of GeO₂ due to its hygroscopic nature. Such microcluster structures shall provide some potential applications for electronic and optical devices on Si platform.</p>

Electrodeposited Germanium On Silicon Substrate Using A Mixture Of Germanium Tetrachloride And Propylene Glycol

We report the deposition of germanium (Ge) film on silicon (Si) substrate by a simple and low cost electrochemical deposition using a mixture of germanium tetrachloride (GeCl4) and propylene glycol (C3H8O2). The effects of deposition environment and applied current density on the properties of deposited Ge films were investigated. Ge film containing germanium dioxide (GeO2) microclusters was obtained for deposition in air-exposed environment while high purity Ge film with no impurity detectable by energy-dispersive x-ray spectroscopy (EDS) was obtained in nitrogen (N2) filled environment. In Raman spectra, N2 exposed sample shows smaller full width at half maximum (FWHM) values of Ge-Ge peak compared to air exposed sample, thereby indicating better crystallinity of Ge. Relatively flat and smooth Ge surfaces with the average roughnesses of 0.828-1.069 nm were obtained for all tested current densities of 10, 20 and 60 mAcm-2. The mean Ge crystallite grain sizes were determined to be in the range of 2-4 nm. In qualitative voltammetry study, two reduction peaks were observed in cyclic voltammograms measurement which confirms that the deposition of Ge at cathode occurs via two reduction processes. It is expected that the impurity-free Ge film on Si is promising for various device application towards heterogeneous integration on Si platform.