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

The evolution of helium bubbles in purity Mo was investigated by in-situ transmission electron microscopy (TEM) during 30 keV He+ irradiation (at 673 K and 1173 K) and post-irradiation annealing (after 30 keV He+ irradiation with the fluence of 5.74 × 1016 He+/cm2 at 673 K). Both He+ irradiation and subsequently annealing induced the initiation, aggregation, and growth of helium bubbles. Temperature had a significant effect on the initiation and evolution of helium bubbles. The higher the irradiation temperature was, the larger the bubble size at the same irradiation fluence would be. At 1173 K irradiation, helium bubbles nucleated and grew preferentially at grain boundaries and showed super large size, which would induce the formation of microcracks. At the same time, the geometry of helium bubbles changed from sphericity to polyhedron. The polyhedral bubbles preferred to grow in the shape bounded by {100} planes. After statistical analysis of the characteristic parameters of helium bubbles, the functions between the average size, number density of helium bubbles, swelling rate and irradiation damage were obtained. Meanwhile, an empirical formula for calculating the size of helium bubbles during the annealing was also provided.

In-situ TEM observation of the evolution of helium bubbles in Mo during He+ irradiation and post-irradiation annealing*

Effect of helium and its synergism with displacement damage on microstructure of CLAM steel investigated by single, sequential and simultaneous Fe and He ion irradiations

A good understanding of the chemical disorder in silicon carbide (SiC) after ion irradiation is crucial for evaluating structural stability in both semiconductor and nuclear power systems. In this study, 6H-SiC single-crystal was irradiated with 500 keV He and 2.5 MeV Fe ions at room temperature, followed by annealing at 1500 °C for 2 h. The chemical disorders were investigated by electron energy-loss spectroscopy with the transmission electron microscopy at 200 kV. Facetted voids were found in the end region of the damaged layer. Compared with the substrate region, the Si at.% was lower, while the values of C and O at.% were higher, in particular in inner voids. SiCOx (x < 1) bonds at the inner surface of the voids were detected. The energy losses of Si, C edges shifted to be lower in the damaged layer. The possible reason is discussed, and the research results will be used for understanding the ion irradiation-induced damage in SiC.

/pdf/chemical-disorder-in-6h-sic-irradiated-with-both-he-and-fe-1tx5lg85.pdf

Chemical Disorder in 6H-SiC Irradiated with Both He and Fe Ions Followed by 1500 °C Annealing: Electron Energy-Loss Spectroscopy Analysis

Helium and strontium co-implantation into SiC at room temperature and isochronal annealing: Structural evolution of SiC and migration behaviour of strontium

https://iopscience.iop.org/article/10.1088/1674-1056/abc2b4/pdf

Comparison of helium bubble formation in F82H, ODS, SIMP and T91 steels irradiated by Fe and He ions simultaneously

Optical spectroscopy study of damage evolution in 6H-SiC by {{H}}_{2}(+) implantation

Silicon carbide (SiC) is an important material used in semiconductor industries and nuclear power plants. SiC wafer implanted with H ions can be cleaved inside the damaged layer after annealing, in order to facilitate the transfer of a thin SiC slice to a handling wafer. This process is known as “ion-cut” or “Smart-Cut”. It is worth investigating the exfoliation efficiency and residual lattice defects in H-implanted SiC before and after annealing. In the present paper, lattice damage in the 6H-SiC implanted by H2+ to a fluence of 5 × 1016 H2+/cm2 at 450 and 900 °C was investigated by a combination of Raman spectroscopy and transmission electron microscopy. Different levels of damage caused by dynamic annealing were observed by Raman spectroscopy and transmission electron microscopy in the as-implanted sample. Atomic force microscopy and scanning white-light interferometry were used to observe the sample surface morphology. Surface blisters and exfoliations were observed in the sample implanted at 450 °C and then annealed at 1100 °C for 15 min, whereas surface blisters and exfoliation occurred in the sample implanted at 900 °C without further thermal treatment. This finding can be attributed to the increase in the internal pressure of platelets during high temperature implantation. The exfoliation efficiency, location, and roughness after exfoliation were investigated and possible reasons were discussed. This work provides a basis for further understanding and improving the high-efficiency “ion-cut” technology.

Lattice Defects and Exfoliation Efficiency of 6H-SiC via H2+ Implantation at Elevated Temperature.

The effect of cavities on recrystallization growth of amorphous SiC induced by a high fluence He implantation was investigated. 300 keV He ions were used to implant the 6H-SiC (0001) wafer to a fluence of 4.4 × 1017/cm2 at room temperature. A buried amorphous layer with a width of approximately 468 nm was formed. Moreover, many spherical bubbles with diameters over 25 nm were observed by transmission electron microscopy. Recrystallization of the buried amorphous layer was visible after 900 °C annealing for 30 min. Some irregular cavities were found in the damaged layer. The recrystallization started from the amorphous/crystalline interface, and the formed cavities retarded the epitaxial growth. Nanocrystalline SiC was formed in the cavity layer. Extended defects were also characterized by transmission electron microscopy. The research results will give an insight into the recrystallization process in amorphous SiC.

Shuai Xu

Papers

Comparison of helium bubble formation in F82H, ODS, SIMP and T91 steels irradiated by Fe and He ions simultaneously

Optical spectroscopy study of damage evolution in 6H-SiC by {{H}}_{2}(+) implantation

Lattice Defects and Exfoliation Efficiency of 6H-SiC via H2+ Implantation at Elevated Temperature.

The effect of cavities on recrystallization growth of high-fluence He implanted-SiC

Effect of irradiation temperature on radiation hardening of CLF-1 steel