Chemistry Nexus

Workers in Russia and Los Alamos, USA report in Nature¹ superconductivity in boron-doped diamond synthesized at high pressure (nearly 100,000 atmospheres) and temperature (2500-2800 K). Electrical resistivity, magnetic susceptibility, specific heat and field-dependent resistance measurements show that boron-doped diamond (carbon) is a bulk, type-II superconductor below the superconducting transition temperature T_c 4 K.

Boron has one less electron than carbon and, because of its small atomic radius, is relatively easily incorporated into diamond. The boron acts as a charge acceptor and the resulting diamond is effectively hole-doped.¹

Abstract: Diamond is an electrical insulator well known for its exceptional hardness. It also conducts heat even more effectively than copper, and can withstand very high electric fields. With these physical properties, diamond is attractive for electronic applications, particularly when charge carriers are introduced (by chemical doping) into the system. Boron has one less electron than carbon and, because of its small atomic radius, boron is relatively easily incorporated into diamond; as boron acts as a charge acceptor, the resulting diamond is effectively hole-doped. Here we report the discovery of superconductivity in boron-doped diamond synthesized at high pressure (nearly 100,000 atmospheres) and temperature (2,500–2,800 K). Electrical resistivity, magnetic susceptibility, specific heat and field-dependent resistance measurements show that boron-doped diamond is a bulk, type-II superconductor below the superconducting transition temperature T_c about 4 K; superconductivity survives in a magnetic field up to H_c2(0) 3.5 T. The discovery of superconductivity in diamond-structured carbon suggests that Si and Ge, which also form in the diamond structure, may similarly exhibit superconductivity under the appropriate conditions.

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