Defect evolution in nitrogen-implanted CVD diamond during thermal annealing
The formation of NV centers and vacancy clusters
Marcel Dickmann (Université d'Orléans, University of the Federal Armed Forces Munich)
Ricardo Helm (University of the Federal Armed Forces Munich)
Werner Egger (University of the Federal Armed Forces Munich)
Johannes Mitteneder (University of the Federal Armed Forces Munich)
Peter Sperr (University of the Federal Armed Forces Munich)
Michael Mayerhofer (University of the Federal Armed Forces Munich)
Maik Butterling (TU Delft - RID/TS/Instrumenten groep)
Eric Hirschmann (Helmholtz Zentrum Dresden Rossendorf)
Maciej Oskar Liedke (Helmholtz Zentrum Dresden Rossendorf)
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Abstract
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 0.5MeVN+ ions at a fluence of 1×1014cm−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 ∼ppm levels together with a low concentration of larger vacancy clusters. Nitrogen implantation increases the abundance of mono-/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 grow 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. At annealing above 1000∘C, positron annihilation occurs predominantly in perfect bulk or 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.
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