Interplay between atomic disorder, lattice swelling, and defect energy in ion-irradiation-induced amorphization of SiC

Abstract

A combination of experimental and computational evaluations of disorder level and lattice swelling in ion-irradiated materials is presented. Information obtained from X-ray diffraction experiments is compared to X-ray diffraction data generated using atomic-scale simulations. The proposed methodology, which can be applied to a wide range of crystalline materials, is used to study the amorphization process in irradiated SiC. Results show that this process can be divided into two steps. In the first step, point defects and small defect clusters are produced and generate both large lattice swelling and high elastic energy. In the second step, enhanced coalescence of defects and defect clusters occurs to limit this increase in energy, which rapidly leads to complete amorphization.2

Statistical Nature of Atomic Disorder in Irradiated Crystals

“…Concomitantly, as mentioned above, the elastic strain in the crystalline regions increases with the ion fluence. Therefore, these two findings indicate that the volume of the strained, crystalline regions decreases with irradiation dose, with the concomitant formation of amorphous regions (in perfect agreement with the results presented in [27] where only the 004 reflection was probed).…”

“…In the Gaussian case, even for the highest disorder level, atomic rows are still visible ( Fig. 2(e)), which is in contrast with the actual microstructure of the samples at this fluence, as previously shown in [22,27]. In the case of Lévy-stable distributions, the lowest level of disorder ( Fig.…”

“…This result leads to two important conclusions regarding the irradiation-induced atomic disorder in SiC: (i) it is actually highly non-Gaussian, (ii) its nature changes with increasing fluence, where large displacements become more likely to occur, probably as a consequence of the increasing fraction of amorphous (i.e. completely disordered) regions [27].…”

“…{001}-oriented 3C-SiC single crystals (with lattice parameter a 0 = 4.359 Å) were irradiated with 100 keV Fe ions with ion fluences in the 4 × 10 13 -2 × 10 14 cm -2 range, which corresponds to damage doses of ~0.072 to ~0.36 dpa (displacement per atom) at the damage peak, as determined with the SRIM code [24] using threshold displacement energies of 20 and 35 eV for the C and Si sublattices, respectively [25,26]. Details regarding the irradiation conditions can be found in [22,27].…”

Atomistic modeling of point defect contributions to swelling in Xe-implanted silicon carbide

“…In the case of SiC, irradiation at low temperature, i.e. lower than 250 • C, leads to amorphization [5][6][7]. At higher temperatures, amorphization is prevented by dynamic recovery.…”