Impurity analysis of synthetic diamond for electronics and quantum physics

Diamond is an ultrawide bandgap semiconductor with exceptional physical properties, making it highly suitable for various advanced applications. However, precise doping control remains a challenge, particularly for n-type conductivity due to doping asymmetry. Additionally, in quantum applications, phosphorus donors enhance nitrogen-vacancy center coherence times, requiring precise impurity level control. This work presents a secondary ion mass spectrometry (SIMS) study on impurities analysis in diamond, focusing on hydrogen, boron, carbon isotope, nitrogen, and phosphorus. Using four implanted standards and two lab-grown samples, we optimized SIMS conditions to improve the detection limits and isotopic ratio measurements. We measured a 13C/12C isotopic ratio of ∼0.004% in a 13C-depleted diamond layer. At low mass resolution, we showed detection limits of up to 1.5 × 1016 and 3.0 × 1015 at/cm3 for boron and phosphorus, respectively. For hydrogen, the increase in the sputtering rate enabled us to move from 4.7 × 1018 to 6.3 × 1017 at/cm3. High mass resolution settings enabled phosphorus detection limits to reach above 3.0 × 1014 at/cm3. Concerning nitrogen, we use an ultrapure lab-grown layer to achieve the measurement of a detection limit of 2.3 × 1016 at/cm3, thanks to the raster size reduction. These results provide crucial insights into impurities’ characterization in diamond, supporting advancements in diamond-based electronic and quantum applications.