FTIR study of silicon carbide amorphization by heavy ion irradiations

Abstract

We have measured at room temperature (RT) the Fourier-transform infra-red (FTIR) absorption spectra of ion-irradiated thin epitaxial films of cubic silicon carbide (3C–SiC) with 1.1 µm thickness on a 500 µm thick (1 0 0) silicon wafer substrate. Irradiations were carried out at RT with 2.3 MeV 28Si+ ions and 3.0 MeV 84Kr+ ions for various fluences in order to induce amorphization of the SiC film. Ion projected ranges were adjusted to be slightly larger than the film thickness so that the whole SiC layers were homogeneously damaged. FTIR spectra of virgin and irradiated samples were recorded for various incidence angles from normal incidence to Brewster’s angle. We show that the amorphization process in ion-irradiated 3C–SiC films can be monitored non-destructively by FTIR absorption spectroscopy without any major interference of the substrate. The compared evolutions of TO and LO peaks upon ion irradiation yield valuable information on the damage process. Complementary test experiments were also performed on virgin silicon nitride (Si3N4) self-standing films for similar conditions. Asymmetrical shapes were found for TO peaks of SiC, whereas Gaussian profiles are found for LO peaks. Skewed Gaussian profiles, with a standard deviation depending on wave number, were used to fit asymmetrical peaks for both materials. A new methodology for following the amorphization process is proposed on the basis of the evolution of fitted IR absorption peak parameters with ion fluence. Results are discussed with respect to Rutherford backscattering spectrometry channeling and Raman spectroscopy analysis.

Transmission electron microscopy study of extended defect evolution and amorphization in SiC under Si ion irradiation

“…In order to address these issues, transmission electron microscopy (TEM/HRTEM) results are reported on virgin and ion‐irradiated 3C‐SiC epilayers on a Si substrate. Those data are found to be consistent with the previous FTIR spectroscopy data 28 . The evolution of native SFs of the pristine 3C polytype and its impact on radiation damage are discussed.…”

“…This was also accompanied by an increase in the backscattering yield in Rutherford backscattering spectroscopy‐channeling (RBS/C) experiments on 6H‐SiC single crystals, corresponding to disorder build‐up in the Si sublattice 23,27 . FTIR spectroscopy data have also shown a progressive decrease and broadening of the TO (at 790 cm −1 ) and LO (at 970 cm −1 ) phonon peaks of 3C‐SiC epilayers that are consistent with the former results by Raman spectroscopy finding a threshold amorphization fluence corresponding to ~0.3‐0.4 displacement per atom (dpa) 28 …”

Raman study of amorphization in nanocrystalline 3C–SiC irradiated with C+ and He+ ions

“…The amorphous Si–C band is composed of two broad peaks at 766 and 870 cm −1 , as assumed in a previous report . These two peaks are most likely induced by the progressive broadening and redshift of the Si–C TO and LO peaks with ion fluence . Therefore, the Si–C band areas (except for the 655‐cm −1 peak) were used to estimate the damage level in SiC, as discussed below.…”

“…[15] These two peaks are most likely induced by the progressive broadening and redshift of the Si-C TO and LO peaks with ion fluence. [26] Therefore, the Si-C band areas (except for the 655-cm −1 peak) were used to estimate the damage level in SiC, as discussed below. For homonuclear C-C bonds, it is not clear whether the D and G peaks involving graphite structures are first produced at low fluences, as observed in the case of the ion-irradiated 6H-SiC, [14] because the signalto-noise ratio of the C-C bands is quite low in this study.…”

Influence of the free-electron concentration on the optical properties of zincblende GaN up to 1×1020cm−3

“…The final results of our spectroscopic ellipsometry analysis are DFs (model and pbp fitted) for the differently high doped c-GaN layers. The substrate was already thoroughly investigated earlier [43][44][45][46][47].…”