Enhanced 395nm ultraviolet photoluminescence(PL) has been obtained from the SiO

2

/Ge:SiO

2

/SiO

2

sandwiched structure.As light source for optical data storage system

this structure will be very useful in optoelectronic integration.Simultaneously

infrared light emission peaked at 780nm was also observed in this novel structure.In this paper

we discussed the origin of the infrared PL in terms of infrared spec-troscopy(FT-IR) and FL excitation(PLE) spectra.The constancy of the 780nm PL band with annealing temperature does suggest that it can not arise from both the quantum confinement on Ge

Si nanocrystals and the oxygen deficient defects of Ge and Si

because PL from these radiative centers all have peak shifts to some extent.The experimental results from FT-IR strongly suggest that the Ge-O-Ge vibration intensity and the 780nm PL intensity have a similar behavior with annealing temperature.So it is reasonable to be-lieve that the infrared PL band is very related to Ge oxides.Further PLE examination results indicate that it has the similar excitation process to the 395nm ultraviolet PL which comes from TⅡ'(T)→S

0

optical transitions in GeO color centers

which has been confirmed by many research groups.So we believe that the 780nm PL should also originate from GeO color centers.The schematic diagram of electronic states of GeO molecule is presented to describe the carriers' excitation and recombination process in this kind of centers.The TⅡ'→S0 optical transitions in GeO color center is responsible for the infrared PL.In GeO molecules

all radiative transitions are intramolecular.Thus the PL bands from the GeO color centers are hardly influ-enced by the SiO

2

network.That is why 780nm infrared PL has no wavelength change with different annealing temperature.Our work paves the way for the sandwiched structure's device applications.