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SiO 2 /Ge:SiO 2 /SiO 2 sandwiched structure was fabricated for exploring efficient light emission. After annealed in N 2 (O 2 Ͻ1%), this structure shows three photoluminescence ͑PL͒ bands at 293, 395, and 780 nm. The intensity of the 395 nm band is largely enhanced in comparison with that from the monolayered Ge:SiO 2 film. Spectral analyses suggest that the three PL bands originate from S 1 →S 0 , T ͚ (T ͟)→S 0 , and T ͟ Ј →S 0 optical transitions in GeO color centers, respectively. The improvement of the GeO density resulting from the confinement on Ge diffusion is responsible for the enhanced ultraviolet PL. This structure is expected to have important applications in optoelectronics.

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