He Beam Annealing And Self-Healing Of Kr Implanted Bawo4 At Low Temperature

Damage formation in 370 keV Kr ion-implanted BaWO4 is investigated with Rutherford backscattering spectrometry in channeling mode (RBS/C), performed in a quasi-in situ modus at a cryogenic temperature of 16 K. The obtained results are compared to those for similar experiments done previously at room temperature. The significant differences observed for ion implantation into BaWO4 at these two temperatures can be explained by the mobility of WO3 impurities. Other authors found WO3 to become mobile at temperatures above 240 K. This defect mobility can further account for the strong damage annealing occurring during warming implanted samples from 16 K to room temperature. In this temperature range, only completely amorphized layers remain stable. However, these layers transform into much less damaged layers exhibiting a strong crystalline long-range order during storage at room temperature with time, revealing a kind of self-healing. Another very important finding is the strong damage annealing due to the analyzing He ions during the RBS/C analysis both at 16 K and at room temperature. The analyzing He ions deposit their energy mainly in the electronic system of the target atoms. By applying an analytical thermal spike model, it is shown that the local temperature increase along the trajectory of the analyzing He ions could be responsible for observed damage annealing. The high susceptibility to energy deposition in electronic processes may have implications for any analysis based on energetic electrons. BaWO4 reveals a high radiation resistance at room temperature, which may be relevant for practical application.