Covert Properties of Diamonds

11 08 2008
Research team headed by Privatdozentin Dr. Natalia Dubrovinskaia (Institute of Earth Sciences, University of Heidelberg) casts light on some of the riddles surrounding boron-doped diamonds — Publication in the current edition of the journal Proceedings of the National Academy of Sciences of the United States (PNAS)
In itself, a diamond is of no interest for microelectronics. It is neither conductive nor superconductive (i.e. a material that conducts electricity without loss). Implanting boron atoms in the surface of a diamond makes it semiconductive, thus enhancing its interest for microelectronics. A German research team has now used ultra-modern investigation techniques to study the superconductive properties of this material. The results can be found in an article in the current edition of the journal Proceedings of the National Academy of Sciences of the United States (PNAS).

A “boron-doped” diamond not only becomes semiconductive, it also displays very good thermoelastic and mechanical properties. In 2004 the discovery was made that boron-doped diamond is in fact superconductive, but up till now the precise connections were unknown. Is superconductivity a universal property of all diamonds or is it the concentration of boron atoms in the diamond grains that determines the temperature at which the compound becomes superconductive? This temperature is known as the transition temperature. Superconductivity normally only manifests itself at very low temperatures.

A research team from Heidelberg, Bayreuth, Potsdam and Dresden has used investigative techniques like high-resolution transmission electron spectroscopy and electron energy-loss spectroscopy to cast light on some of the mysteries surrounding boron-doped diamonds. Mineral physicist Dr. Natalia Dubrovinskaia first exposed the compound to high pressure and very high temperatures, thus simulating the conditions prevailing in the interior of the Earth. With sophisticated investigation techniques the research team from the Universities of Heidelberg and Bayreuth, the GeoResearchCentre Potsdam (GFZ) and the Dresden-Rossendorf Research Centre (FZD) established that the superconductivity of boron-doped diamond is not dependent on the boron concentration in the diamond. In fact, the diamond grains studied only displayed a very small amount of boron, which contradicts hitherto prevailing scientific opinion. Also, close inspection of the microstructure revealed for the first time that the boron between the diamond grains is amorphous, i.e. has no ordered structure.

“These findings provide new insights into the superconductive properties of diamonds,” says Dr. Natalia Dubrovinskaia of the mineral physics research team at the Institute of Earth Sciences, University of Heidelberg. “This is a highly surprising and unexpected outcome. Our findings herald a complete change in the direction of investigations in the field of superconductive materials containing diamonds. It opens up entirely new perspectives for the synthesis of super-hard and superconductive nano-composites.”

Publication: N. Dubrovinskaia, R. Wirth, J. Wosnitza, T. Papageorgiou,
H.F. Braun, N. Miyajima, L. Dubrovinsky, “An insight into what superconducts in polycrystalline boron-doped diamonds based on investigations of microstructure”, in: PNAS — Proceedings of the National Academy of Sciences of the United States, August 2008 (

Priv.-Doz. Dr. Natalia Dubrovinskaia
Mineral Physics Research Group
Institute of Earth Sciences
University of Heidelberg
Im Neuenheimer Feld 236
D-69120 Heidelberg
phone: 06221/548633
mobile: 0160-92407359

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