Structural Analysis and Electrical Characterization of Heavily Phosphorus‐Implanted Diamond at Elevated Temperature

Heavy phosphorus‐ion implantation into single‐crystal diamond is performed at room temperature and 800 °C, followed by annealing at 1300 °C. The sheet resistance of phosphorus‐implanted diamond is measured using the van der Pauw method. Under room‐temperature implantation, the sheet resistance drastically decreases to 1.5 × 10 ²  Ω/□ at a phosphorus concentration of 8 × 10 ¹⁹  cm ⁻³ due to graphitization of the implanted layer. In contrast, under implantation at 800 °C, the sheet resistance gradually decreases with increasing phosphorus concentration, reaching 5 × 10 ¹⁰  Ω/□ at 4 × 10 ²¹  cm ⁻³ . Raman scattering spectroscopy reveals that the diamond phase remained after heavy phosphorus implantation at 800 °C. However, n‐type conduction due to phosphorus donors is not observed by Hall effect measurements. Rutherford backscattering spectrometry reveals that the concentration of phosphorus atoms at substitutional sites is estimated to be 3–5 × 10 ²⁰  cm ⁻³ for the sample implanted at 8 × 10 ²⁰  cm ⁻³ , whereas accurate estimation becomes difficult at higher implantation concentrations due to substantial lattice disorder. Comparison with heavily carbon‐implanted diamond indicates that electrical conduction in heavily phosphorus‐implanted diamond is dominated by hopping conduction through the defects induced by the ion implantation.