Recovery of ion-damaged 4H-SiC under thermal and ion beam-induced ultrafast thermal spike-assisted annealing

Abstract

The recovery effect of isochronal thermal annealing and inelastic energy deposited during 100 MeV Ag swift heavy ion (SHI) irradiation is demonstrated in the case of 4H-SiC pre-damaged by elastic energy deposition of 300 keV Ar ion. The Ar-induced fractional disorder follows a nonlinear two-step damage build-up. The fractional disorder level of 0.3 displacements per atom (dpa) is established as the threshold above which the lattice rapidly enters the amorphous phase, characterized by the presence of highly photo-absorbing defects. The SHI-induced recovery suggests that the damage annealing, in the pre-damaged region (∼350 nm) where the Se for 100 MeV Ag is almost constant (∼16.21 keV/nm), is more pronounced than the damage creation by SHI. This allows the disorder values to saturate at a lower value than the present initial disorder. Furthermore, the thermal effect due to SHI irradiation of an amorphous nano-zone embedded in a crystalline host matrix has been evaluated using the 3D implementation of the thermal spike. The recovery process by SHI is ascribed to the thermal spike-induced atomic movements resulting from the melting and the resolidification of the crystalline–amorphous interface.

Monitoring of the recovery of ion-damaged 4H-SiC with in situ synchrotron X-ray diffraction as a tool for strain-engineering

“…The extent of recovery is found to depend on the amount of surrounding crystalline regions around the amorphous/disordered regions, as evident from the higher recovery observed at the boundaries of the crystalline-amorphous region as compared to the centre. This is consistent with previous studies where it has been concluded that epitaxial recrystallization requires a sufficient amount of crystalline surroundings that acts as the deciding factor for the extent of observed damage recovery [10,11,29,30]. Annealing at 1273 K for 30 min recovers significant damage, however, the RBS/C yield remains much greater than that of the pristine.…”

“…A last result to point out is the difference between the 0.7 and 1 dpa irradiated crystals. Indeed, both exhibit an amorphous structure, as shown by RBS/C [11] but, as mentioned earlier, due to the high sensitivity of the synchrotron measurement, it is here possible to discriminate between the two, as a clear difference in the Debye-Wallor factor is readily observed in the 20-180 nm region (see Figure 2(c)).…”

“…Before and after thermal annealing, the calculated disorder values from Raman data are 0.39 and 0.18, respectively. The disorder from Raman is estimated as 1-A, where A is the sum of the area under the first-order Raman modes in the irradiated material normalized with respect to that of the pristine crystal [10,11,17]. The percentage of recovery calculated in this case is 52.1%.…”

“…Also, we recently verified that the rapid thermal-spike caused by the strong ionizing energy deposited by 100 MeV Ag ions results in structural and chemical damage recovery in 4H-SiC [10]. Besides, the role of swift heavy ion irradiation in the generation of controlled defects has also been studied [11]. Further, we have also investigated thermal and ion beam-induced ultrafast thermal spike-assisted annealing of pre-damaged 4H-SiC with initial damage as 0.3 dpa (dpa; displacement per atom, 1 dpa = all atoms are displaced at least once from their respective lattice sites) [12,13].…”

“…Annealing at 1273 K for 30 min recovers significant damage, however, the RBS/C yield remains much greater than that of the pristine. To quantitatively assess damage annealing, recovery percentage [10,11] is estimated to be 54.4%. The recovery percentage is evaluated using the data shown in Figure 1(b).…”