Density-Functional Study of the Si/SiO2 Interfaces in Short-Period Superlattices: Vibrational States and Raman Spectra

Raman spectroscopy has proven its effectiveness as a highly informative and sensitive method for the nondestructive analysis of layered nanostructures and their interfaces. However, there is a lack of information concerning the characteristic phonon modes and their activity in Si/SiO2 nanostructures. In order to overcome this problem, the phonon states and Raman spectra of several Si/SiO2 superlattices (SL) with layer thicknesses varied within 0.5-2 nm are studied using DFT-based computer modeling. Two types of structures with different interfaces between crystalline silicon and SiO2 cristobalite were studied. A relationship between the phonon states of heterosystems and the phonon modes of the initial crystals was established. Estimates of the parameters of deformation potentials are obtained, with the help of which the shifts of phonon frequencies caused by elastic strains in the materials of the SL layers are interpreted. The dependence of intense Raman lines on the SL structure has been studied. Several ways have been proposed to use this information, both for identifying the type of interface and for estimating the structural parameters. The obtained information will be useful for the spectroscopic characterization of the silicon/oxide interfaces.

Automated summary

Raman spectroscopy is an effective method for analyzing layered nanostructures and their interfaces. However, there is a lack of information on the phonon modes and their activity in Si/SiO2 nanostructures. This study uses computer modeling to investigate the phonon states and Raman spectra of Si/SiO2 superlattices with varying layer thicknesses. The obtained information can be used to characterize the silicon/oxide interfaces spectroscopically.