Study of thermoluminescence property of C⁺ ion doped anodized alumina

The application of thermoluminescence (TL) has created immense interest due to their potential to determine radiation doses for food-safety, radiation therapy, personal dosimetry, environmental monitoring, etc. However, the performance of a phosphor relies on thermally stimulated light emission from luminescent centres created during the exposure to an ionizing radiation. Aluminum oxide (Al₂O₃) is one of the promising materials for dosimetry. Although this material was forgotten for a long time due to its low sensibility compared with that of TLD-100, it recently regained interest owing to the development of anion defects in Al₂O₃:C single crystals. It was reported to be highly sensitive, even more than TLD-100, though conventional crystal growth technique requires high temperature in the presence of a high tumbling atmosphere. Nevertheless, the TL sensitivity of crystalline Al₂O₃ can be enhanced by doping with carbon, but this is only good for low dose radiation monitoring (typically 0.1-100 Gy). Interestingly, a prominent TL sensitivity can be achieved from nanocrystals with increasing surface-to-volume ratio because of increasing surface states. Therefore, judicial use of Al₂O₃ nanocrystallites will give a fertile ground for offline dose monitoring. The nanotrenches of anodized alumina in this respect can also give additional path for improving efficiency, which can be enhanced further by controlled introduction of C in Al₂O₃ matrix. Since ion beam implantation is known to be a powerful method because of its ability to control over distribution of dopants and residual defects, it is therefore important to understand the impact of C⁺ ions in controlling the formation of traps in anodized alumina and also to explore its suitability for ion beam dosimetry by following the TL glow curves with increasing fluence (i.e. ions/cm²).
To execute this plan, after optimizing the porosity, the penetration depth of C⁺ ions in Al₂O₃ layers have been calculated by SRIM. Typical porous structure in the present set of samples is shown in Figs. 1 and 2. Based on this understanding, the anodized alumina has been exposed to 50 keV C⁺ ions in the fluence range of 2.33×10¹⁵ to 1.3×10¹⁶ ions/cm². Following the initial structural analysis by XRD, TL response of the ion irradiated samples was characterized, showing a systematic rise in intensity with increasing fluence (Figure 3). For understanding of the underlying process, the anodized alumina before and after irradiation have now been studied by various techniques, like SEM, TEM, XRD, RBS, and XPS.