Microstructure of swift heavy ion irradiated SiC, Si{sub3N{sub}4 and AIN

摘要

Cross-section transmission electron microscopy was used to investigate the microstructure of single crystal silicon carbide and polycrystalline silicon nitride and aluminum nitride following room temperature irradiation with either 245 MeV Kr or 710 MeV Bi ions. The fluences ranged from 1×10{sup}12/cm{sup}2 (single truck regime) to 1×10{sup}13/cm{sup}2. Ion truck formation was observed in the Bi ion-irradiated Si{sub}3N{sub}4 specimen in regions where the electronic stopping power exceeded a critical value of ～15 keV/nm (depths <24 μm). Ion truck formation was not observed at any depth in 245 MeV Kr ion-irradiated Si{sub}3N{sub}4, in which the maximum electronic stopping power was 14.5 keV/nm. There was no evidence for track formation in either SiC or AlN irradiated with 710 MeV Bi ions, which indicates that the threshold electronic stopping power for track formation in these two ceramics is >34 keV/nm. The high resistance of SiC and AlN to truck formation may be due to their high thermal conductivity, but further study is needed to quantitatively evaluate the suitability of the various truck formation models.