The synthesis of diamonds in traditional growth systems based on Fe, Co and Ni does not allow overcoming the semiconductor level of boron doping of diamond, presumably because of a high affinity of boron to boride-forming metals. For the first time, noble metals that do not form borides—silver and gold—are used as growth media for the synthesis of heavily boron-doped diamonds at 8–9 GPa. Gold and silver are not catalysts for the transformation of graphite to diamond, whereas elemental boron is catalytically active at eutectic melting temperatures above 2500 K. It is found that the synthesis of diamond in AgB and AuB growth media starts at temperatures close to the melting temperatures of Ag and Au, 1600 and 1800 K, respectively. Calculations show that molten Au and Ag dissolve boron atoms without a significant change in the electronic structure of the solution, suggesting that the metal melts serve as a carrier for the boron catalyst. The resulting polycrystalline diamond contains dispersed inclusions of Ag and Au, as well as traces of boron carbide; the formation of borides is not detected. The transport measurements of the diamond samples reveal a transition to a superconducting state in the temperature range from 4.5 to 2.5 K. Raman spectroscopy confirms the heavy boron doping of diamond. Thus, we show that melts of “non-catalytic” metals that do not form borides can be effectively used to synthesize boron-doped conductive/superconducting diamonds at relatively low temperatures.

在基于 Fe、Co 和 Ni 的传统生长系统中合成金刚石无法克服金刚石硼掺杂的半导体水平，大概是因为硼对硼化物形成金属的高亲和力。首次使用不形成硼化物的贵金属（银和金）作为生长介质，在 8-9 GPa 的压力下合成重度硼掺杂金刚石。金和银不是石墨转变为金刚石的催化剂，而元素硼在共晶熔化温度高于 2500 K 时具有催化活性。研究发现，Ag B 和 Au B 生长介质中金刚石的合成开始于接近Ag 和 Au 的熔化温度分别为 1600 K 和 1800 K。计算表明，熔融的金和银溶解了硼原子，而溶液的电子结构没有发生显着变化，这表明金属熔体可以作为硼催化剂的载体。所得的多晶金刚石含有分散的 Ag 和 Au 夹杂物，以及微量的碳化硼；没有检测到硼化物的形成。金刚石样品的传输测量揭示了在 4.5 至 2.5 K 温度范围内向超导态的转变。拉曼光谱证实了金刚石的重硼掺杂。因此，我们表明，不形成硼化物的“非催化”金属熔体可以有效地用于在相对较低的温度下合成掺硼导电/超导金刚石。