SiO/SiO_2超晶格结构界面发光的研究

利用热蒸发技术在硅衬底上制备了层厚不同的SiO/SiO2超晶格样品.对其光致发光谱进行研究发现,随着SiO/SiO2超晶格中SiO层厚度的增加,发光峰在400～600 nm之间移动.研究表明,样品的发光中心来自于SiO/SiO2界面处的缺陷发光(界面态发光).即在样品沉积的过程中,在SiO/SiO2的界面处由于晶格的不连续性,会形成大量的Si-O悬挂键,这些悬挂键本身相互结合可以形成一定数量的缺陷,同时由于O原子容易脱离Si原子的束缚而产生扩散,因此,这些悬挂键可以与扩散的O原子结合,随着SiO层厚度的增加,在SiO/SiO2的界面处先后出现WOB(O3<≡Si-O-O·),NOV(O3≡Si-Si≡O3),E'中心(O≡Si·),NBOHC(O3≡Si-O·)等缺陷,这些缺陷在SiO层厚度增大的过程中对发光先后起到主导作用,从而使得发光峰产生红移.

Photoluminescence from Interface of SiO/SiO_2 Superlattices

SiO/SiO2 superlattices with different thickness of SiO and SiO2 films were deposited on the Si substrates at 200 ℃ 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 SiO2 films. The deconvolution of the PL spectra showed that the WOB(O3≡Si—O—O·), NOV(O3≡Si—Si≡O3), the E′center(O≡Si·)and NBOHC (O3≡Si—O·)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 Si6 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 Si6 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 PL.