We investigate the thermal evolution of implantation-induced defects in single-crystal CVD diamond using depth-resolved positron annihilation lifetime spectroscopy (PALS). Samples were implanted with 0.5 MeV N⁺ ions at a fluence of 1 × 10¹⁴ cm⁻² and annealed between 600 °C and 1200 °C. We probe defect populations as a function of depth and quantify their types and concentrations. In the pristine material, small vacancies, predominantly divacancies, are detected at approximately ppm levels together with a low concentration of larger vacancy clusters. Nitrogen implantation increases the abundance of mono- and divacancies. In nitrogen-rich regions, fewer isolated vacancies are observed despite higher displacement damage. Upon annealing, small vacancies become mobile. In nitrogen-poor regions, they agglomerate and enlarge pre-existing clusters. In contrast, in nitrogen-rich zones, they are efficiently captured by substitutional nitrogen to form NV centers, which limits the formation of new vacancy clusters. After annealing above 1000 °C, positron annihilation occurs predominantly in the perfect bulk crystal or in small open-volume defects consistent with NV center-related positron lifetimes. These results reveal a nitrogen-content- and temperature-dependent competition between vacancy clustering and NV center formation.     «

We investigate the thermal evolution of implantation-induced defects in single-crystal CVD diamond using depth-resolved positron annihilation lifetime spectroscopy (PALS). Samples were implanted with 0.5 MeV N⁺ ions at a fluence of 1 × 10¹⁴ cm⁻² and annealed between 600 °C and 1200 °C. We probe defect populations as a function of depth and quantify their types and concentrations. In the pristine material, small vacancies, predominantly divacancies, are detected at approximately ppm levels togeth...     »