Photo-oxidation of Ge Nanocrystals: Kinetic Measurements by InSitu Raman Spectroscopy

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Ge nanocrystals are formed in silica by ion beam synthesis and are subsequently exposed by selective HF etching of the silica. Under ambient conditions, the exposed nanocrystals are stable after formation of a protective native oxide shell of no more than a few monolayers. However, under visible laser illumination at room temperature and in the presence of O{sub 2}, the nanocrystals rapidly oxidize. The oxidation rate was monitored by measuring the Raman spectra of the Ge nanocrystals in-situ. The intensity ratio of the anti-Stokes to the Stokes line indicated that no significant laser-induced heating of illuminated nanocrystals occurs. Therefore, the ... continued below

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Sharp, I.D.; Xu, Q.; Yuan, C.W.; Beeman, J.W.; Ager III, J.W.; Chrzan, D.C. et al. November 22, 2006.

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Ge nanocrystals are formed in silica by ion beam synthesis and are subsequently exposed by selective HF etching of the silica. Under ambient conditions, the exposed nanocrystals are stable after formation of a protective native oxide shell of no more than a few monolayers. However, under visible laser illumination at room temperature and in the presence of O{sub 2}, the nanocrystals rapidly oxidize. The oxidation rate was monitored by measuring the Raman spectra of the Ge nanocrystals in-situ. The intensity ratio of the anti-Stokes to the Stokes line indicated that no significant laser-induced heating of illuminated nanocrystals occurs. Therefore, the oxidation reaction rate enhancement is due to a photo-chemical process. The oxidation rate varies nearly linearly with the logarithm of the laser intensity, and at constant laser intensity the rate increases with increasing photon energy. These kinetic measurements, along with the power dependencies, are described quantitatively by an electron active oxidation mechanism involving tunneling of optically excited electrons through the forming oxide skin and subsequent transport of oxygen ions to the Ge nanocrystal surface.

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  • 2006 Materials Research Society (MRS) FallMeeting, Boston, MA, November 27-December 1, 2006

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  • Report No.: LBNL--62294
  • Grant Number: DE-AC02-05CH11231
  • Office of Scientific & Technical Information Report Number: 928233
  • Archival Resource Key: ark:/67531/metadc896403

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  • November 22, 2006

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  • Sept. 27, 2016, 1:39 a.m.

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  • Oct. 31, 2016, 3:55 p.m.

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Sharp, I.D.; Xu, Q.; Yuan, C.W.; Beeman, J.W.; Ager III, J.W.; Chrzan, D.C. et al. Photo-oxidation of Ge Nanocrystals: Kinetic Measurements by InSitu Raman Spectroscopy, article, November 22, 2006; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc896403/: accessed November 12, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.