**5. Conclusions**

The exfoliation e fficiency of H2 + implantation at 450 ◦C and 900 ◦C to a fluence of 5 × 10<sup>16</sup> H2/cm<sup>2</sup> in 6H-SiC was investigated. A lattice swelling of 5% was observed in the H2 +-implanted 6H-SiC at 450 ◦C. Reverse dynamic annealing was observed in the H2 +-implanted 6H-SiC at 900 ◦C. This is related to the rapid growth of hydrogen and vacancy clusters (HnV m), following by emitting interstitials around HnV m. A microcrack was observed in the front of the damage band in the sample implanted with H2 + ions at 450 ◦C and subsequently annealed at 1100 ◦C for 15 min. In the sample implanted with H2 + ions at 900 ◦C, a microcrack occurred between the displacement damage peak and the maximum hydrogen deposition. The change in specific interface energy γ can explain the location of the microcrack. Despite a high e fficiency of exfoliation in the sample implanted at 900 ◦C, this procedure is not considered optimal for the fabrication of the SiCOI structure due to a wide damage band formed during H2 + implantation. Instead, we propose hydrogen implantation at a temperature lower than the critical temperature for vacancy migration as a more suitable method for this purpose.

**Author Contributions:** Data curation and funding acquisition, T.W.; data curation and concepturalization, Z.Y.; original writing & editing, supervision and project administration, B.L.; data curation, S.X. and Q.L.; formal analysis, F.G.; data curation and resources, T.Z. and J.L. All authors have read and agreed to the published version of the manuscript.

**Funding:** The work was funded by the National Natural Science Foundation of China (Grant Nos. U1832133, 11905206), Sichuan Science and Technology Program (Grant No. 2020ZYD055), and the Doctor Research Foundation of Southwest University of Science and Technology (Grant No. 18zx714101).

**Conflicts of Interest:** The authors declare no conflict of interest.
