Effect of B–O co-doping on the properties of HPHT diamond single crystals in the Fe–Ni–C system

Abstract

Boron-doped diamond (BDD) is highly valued for its excellent semiconductor properties, but high boron doping levels often cause lattice distortion and degraded electrical performance. To address this challenge, boron–oxygen (B–O) co-doping was employed to synthesize high-quality single crystals by a high pressure and high temperature (HPHT) method in the Fe–Ni–C system (5.8–6.2 GPa, 1360–1440 °C). Using amorphous boron and Fe₃O₄ as dopant sources, crystals with gradient boron concentrations were characterized by FTIR, Raman, XRD, XPS, EPMA and Hall effect measurements. Results confirmed successful B and O incorporation, with oxygen mitigating boron-induced stress. The sample with 5 wt% B and 5 wt% Fe₃O₄ achieved optimal electrical performance: a carrier concentration of 3.76 × 10¹⁸ cm⁻³ and a resistivity of 8.15 × 10⁻¹ Ω cm. Compared to pure BDD, B–O co-doping enhanced carrier mobility and reduced resistivity due to improved crystalline quality. This work provides experimental support for optimizing co-doping processes and advancing high-performance semiconductor diamond materials.