Detection Limit of Phosphorus in Diamond by High Mass Resolution Secondary‐Ion Mass Spectrometry

In diamond, secondary‐ion mass spectrometry (SIMS) is usually performed in order to detect and measure the depth distribution of impurities. The SIMS measurements are then performed using parameters allowing high sensitivities. In the classical configuration for diamond analysis, the mass resolution is usually set at the lowest value and gives access to the concentration of most dopants. In the case of phosphorus, the detection limit is then in the range of a few 1015 at cm−3 (≈20 ppb).Herein, several diamond samples are studied and the SIMS detection on the secondary ions of masses 12 (carbon) and 31 (phosphorus) is focused. It is shown that SIMS analyses require high mass resolution (HMR) to accurately separate unexpected molecular ions detected at 31 a.m.u. In such HMR–SIMS analyses, the detection limit of phosphorus by one decade is improved and the value of 3 × 1014 at cm−3 is achieved. Surprisingly, the detection of phosphorus in diamond by secondary‐ion mass spectrometry (SIMS) is limited by unexpected and not yet identified ions located at the exact mass of phosphorus. The use of high mass resolution (HMR) settings is then essential to measure ultralightly phosphorus‐doped diamond thanks to very low detection limit of phosphorus: 3 × 1014 at cm−3 (≈1–2 ppb).