Photoluminescence from Interface of SiO/SiO2 Superlattices

SiO/SiO2 superlattices, with different thickness of SiO and SiO2 films were deposited on the Si substrates at 200 degrees C by thermo-evaporation technology. The photoluminescence (PL)spectrum centers of the samples shifted from 400 nm to 600 nm with the increase in SiO films thickness. Similar phenomena were also found when increasing the thickness Of SiO2 film but forming SiO film. It was found that the PL was attributed to the defects located at the interfaces between SiO and SiO films. The de-convolution of the PL spectra showed that the WOB(O-3 Si-O-O center dot), NOV(O-3 Si-Si O-3), the E' center(O Si center dot) and NBOHC (O-3 Si-O center dot)defects contributed to the PL spectra. A mass of Si-O dangling bonds formed on the interfaces of the SiO and SiO2 during the deposition process, could provide many free O atoms and intrinsic defects. When the SiO film was thin (such as 1 nm), most of the S rings were broken, and more WOB defects(415 nm) would be formed because of the combination of the intrinsic NBOHC defects and the diffusing O atoms on the interfaces. With the increase in the SiO film thickness, more Si-6 rings were formed in the SiO films, that is the number of the Si-O dangling bonds decreased, less of WOB defects could be formed as both of the free O atoms and intrinsic defects decreased, but the NOV defects(470 nm) increased because of more E' center defects would be combined in pairs. With increasing of the SiO film thickness, the combination of the intrinsic defects became more difficult, so the E' center defects(520 nm)and NBOHC defects(630 nm)would dominate the PL of the SiO/SiO2 superlattices in turn. In conclusion, the evolution of the defects located at the interfaces induced the red shift of the PI..