Preparation And Optical Properties Of One-Dimensional Germanium Dioxide Nanostructures

Nanowires and nanocones of GeO₂ have been prepared by using the in-situthermal oxidation, atmospheric pressure chemical vapor deposition and hydrothermalmethods. The morphologies, crystal structures, Raman and photoluminescenceproperties of nanowires and nanocones of GeO₂ were investigated, and the possiblegrowth mechanisms were also proposed to account for the formation of nanowires andnanocones of GeO₂. A strong UV emission with peak at 355nm was observed in GeO₂nanowires. The structure-property relations were discussed. These investigative resultswould provide a base for research of Photoelectric properties and application of GeO₂nanostructures.(1) GeO₂ nanowires have been in-situ grown on the surface of germaniumsubstrates on a large scale by heating germanium wafers coated with an Au film at550-800℃in an air atmosphere. These GeO₂ nanowires with a hexagonal structurehad a controllable diameter in the range of 110-170 nm with lengths of up to 30micrometers by varying the heating temperature. A possible mechanism was proposedto account for the growth of GeO₂ nanowires, and the effects of phonon confinementon the Raman spectra of GeO₂ nanowires was also observed.(2) GeO₂ nanowires have been in-situ grown on the surface of germaniumsubstrates on a large scale by heating germanium wafers coated with an Au film at600-800℃under the flow of O₂.The GeO₂ nanowires are single crystalline phase withthe hexagonal structure and typical diameters of 65-340 nm and lengths of up to 50micrometers. The influences of the thickness of Au film and the reaction temperatureand time on the diameter development were experimentally investigated, and apossible mechanism was also proposed to account for the formation of GeO₂nanowires. Control over the diameter of nanowire was achieved by adjusting thethickness of Au film and the heating temperature and time. The GeO₂ nanowiresexhibited a strong UV emission with peak at 355nm and a weak blue emission withpeaks at 400 and 485 nm. The UV and blue emissions may be assigned to transitionbetween the oxygen vacancy and interstitial oxygen and radiative recombination between an electron on an oxtygen vacancy and a hole on an germanium-oxygenvacancy center in the GeO₂ nanowires, respectively.(3) GeO₂ nanowires have been in-situ grown on the surface of germaniumsubstrates on a large scale by heating germanium wafers coated with an Au film at600-800℃under the flow of H₂O. The GeO₂ nanowires are single crystalline phasewith the hexagonal structure and had a controllable diameter in the range of 110-160nm with lengths of up to 30 micrometers by varying the thickness of Au film and theheating temperature and time. The growth of GeO₂ nanowires is under the control ofthe Vapor-Liquid-Solid mechanism. A strong UV emission with peak at 355nm and aweak blue emission with peaks at 400 and 485 nm were observed in the GeO₂nanowires. The UV and blue emissions may be assigned to transition between theoxygen vacancy and interstitial oxygen and radiative recombination between anelectron on an oxtygen vacancy and a hole on an germanium-oxygen vacancy center inthe GeO₂ nanowires, respectively.(4) GeO₂ nanowires have been grown on the surface of silicon substrates on alarge scale by an atmospheric pressure chemical vapor deposition method. Theas-synthesized products were characterized by means of powder X-ray diffraction,scanning electron microscopy and transmission electron microscopy. The resultsshowed that the GeO₂ nanowires are single crystalline phase with the hexagonalstructure and typical diameters of 270-500 nm and lengths of up to 13 micrometers.The influences of the heating temperature and time on the diameter development wereexperimentally investigated, and a possible mechanism was also proposed to accountfor the formation of GeO₂ nanocones.(5) GeO₂ nanowires have been prepared through a hydrothermal reaction ofGe(OH)₂ in aqueous solution at 420 or 450℃for 1h. The as-synthesized products werecharacterized by means of powder X-ray diffraction, scanning electron microscopy andtransmission electron microscopy. The results showed that the GeO₂ nanowiresobtained at 420℃are single crystalline phase with the cubic structure and typicaldiameters of 100-190 nm and lengths of up to 3.5 micrometers. The GeO₂ nanowiresobtained at 450℃are hexagonal-cubic GeO₂ heterostructure. The diameters and lengths of the nanowire are 30 nm and 1.5 micrometers, respectively. A possiblemechanism was also proposed to account for the formation of GeO₂ nanowires.