Raman spectroscopy was used to investigate the structure of ion-irradiated α-SiC single crystals at room temperature and 400 °C. Irradiations induce a decrease of the Raman line intensities related to crystalline SiC, the appearance of several new Si–C vibration bands attributed to the breakdown of the Raman selection rules, and the formation of homonuclear bonds Si–Si and C–C within the SiC network. For low doses, the overall sp3 bond structure and the chemical order may be almost completely conserved. By contrast, the amorphous state shows a strong randomization of the Si–Si, Si–C and C–C bonds. The relative Raman intensity decreases exponentially versus increasing dose due to the absorption of the irradiated layer. The total disorder follows a sigmoidal curve, which is well fitted by the direct impact/defect stimulated model. The chemical disorder expressed as the ratio of C–C bonds to Si–C bonds increases exponentially versus the dose. A clear correlation is established between the total disorder and the chemical disorder. The increase of temperature allows the stabilization of a disordered/distorted state and a limitation of damage accumulation owing to the enhancement of the dynamic annealing.

https://iopscience.iop.org/article/10.1088/0953-8984/18/22/022/pdf

Raman spectroscopy study of heavy-ion-irradiated α-SiC

This review is devoted to the analysis of the problems related to fabrication of the Si porous layers. The review was motivated by a great interest to Si-based porous materials from nano- to macro-scale for various applications in electronics, optoelectronics, photonics, chemical sensors, biosensors, etc. The peculiarities of the silicon porosification and the principles of preparing porous layers are considered in the present article. Various methods used for Si porosification such as chemical stain etching, chemical vapor etching, laser-induced etching, metal-assisted etching, spark processing and reactive ion (plasma) etching were analyzed. However, the main attention was focused on electrochemical porosification of Si. The review discusses in detail the influence of parameters such as electrolyte composition and pH, current density, etching time, temperature, wafer doping and orientation, lighting, magnetic field, and ultrasonic agitation on the process of Si porosification. It was shown that the stru...

Silicon Porosification: State of the Art

Raman spectroscopy was used to investigate the structure of ion-irradiated α-SiC single crystals at room temperature and 400 ◦ C. Irradiations induce a decrease of the Raman line intensities related to crystalline SiC, the appearance of several new Si–C vibration bands attributed to the breakdown of the Raman selection rules, and the formation of homonuclear bonds Si–Si and C–C within the SiC network. For low doses, the overall sp 3 bond structure and the chemical order may be almost completely conserved. By contrast, the amorphous state shows a strong randomization of the Si–Si, Si–C and C–C bonds. The relative Raman intensity decreases exponentially versus increasing dose due to the absorption of the irradiated layer. Th et otaldisorder follows a sigmoidal curve, which is well fitted by the direct impact/defect stimulated model. The chemical disorder expressed as the ratio of C–C bonds to Si–C bonds increases exponentially versus the dose. A clear correlation is established between the total disorder and the chemical disorder. The increase of temperature allows the stabilization of a disordered/distorted state and a limitation of damage accumulation owing to the enhancement of the dynamic annealing.

Raman spectroscop ys tudy of heavy-ion-irradiated α-SiC

The Raman spectra of silicon nanoparticles in the size range between d = 3.5 – 60 nm have been studied experimentally. Scattering processes up to second order are being observed. The experimental results are analyzed in the framework of the phonon confinement model. While this model describes qualitatively the observations for first-order scattering processes, it is not applicable for scattering processes of higher order. From the analysis of second-order scattering, we determine a redshift of the TO phonon at the X and L points.

Raman properties of silicon nanoparticles

The red shift and the broadening of the Raman signal from microcrystalline silicon films is described in terms of a relaxation in the q-vector selection rule for the excitation of the Raman active optical phonons. The relationship between width and shift calculated from the known dispersion relation in c-Si is in good agreement with available data. An increase in the decay rate of the optical phonons predicted on the basis of the same model is confirmed experimentally.

The one phonon raman spectrum in microcrystalline silicon

Raman, photoluminescence (PL) and optical absorption results on silicon nanocrystals in SiO2 matrices prepared by RF sputtering method are presented. The samples have varying Si/SiO2 compositional fraction and are annealed at different temperature and duration. The average size of the nanocrystals is determined by the lineshape analysis of the first-order Raman spectra. Raman results further indicate the existence of a threshold annealing temperature for the formation of nanocrystals and increase in the nanocrystal size with increasing temperature and duration. Size-dependent blue shift of the absorption edge is observed from absorption experiments and is supported by Raman results. Room temperature and temperature dependent PL results are analyzed with the help of a phenomenological model. The PL results in conjunction with the Raman and absorption results indicate the involvement of both the core states and the interfacial states in the luminescence process.

K.P Jain

Papers

Raman, photoluminescence and optical absorption studies on nanocrystalline silicon