Photoluminescence and Stability of Sputtered SiOx Layers

SiOx layers with thicknesses of about 300-1000 nm are produced by sputtering silicon onto glass and quartz substrates. Silicon is oxidized during deposition, and the refractive index of the sputtered layers vary from 1.63 to 1.86. Oxygen atomic concentration in SiOx is in the range of 1<1.54. Photoluminescence of SiOx layers is observed and assumed to originate from silicon nanocrystals embedded in a SiOx matrix that is formed after thermal treatment by a Xe flash-lamp. A layer on quartz substrate exhibits the strongest emission and shows Raman spectral peak at 507 cm-1, which is smaller than the value of 521 cm-1 of bulk silicon crystal. Based on this difference, the size of silicon nanocrystals is estimated to be equal to 1.2 nm. The photoluminescence spectrum consists of overlapping Gaussian functions indicating the size distribution of the silicon nanocrystals. Mean silicon nanocrystals size in the layer on a quartz substrate is estimated at 1.4 nm from the photoluminescence peak datasets reported in previous researches. Thus, sputtering of silicon in a low-pressure air and subsequent flash-heating seems to be a convenient method to produce silicon nanocrystals in SiOx layers. These could be useful to realize Si-LEDs or even silicon lasers. In addition, the aging of SiOx layers during 6 months is evaluated.

Automated summary

SiOx layers with thicknesses of 300-1000 nm are produced by sputtering silicon onto glass and quartz substrates. Silicon is oxidized during deposition, leading to the formation of silicon nanocrystals in SiOx matrix after flash heating. The photoluminescence of the layers indicates potential applications, such as Si-LEDs or silicon lasers.