Ultrathin Layer of Rhenium Is the New Superconductor

The superconductor has potential applications in the next generation of circuit boards, which could result in ultrafast computing devices. (Image courtesy of David Parker/IMI/University of Birmingham High Tc Consortium/Science Photo Library.)

Superconductor materials conduct electricity with zero resistance when external magnetic fields will not penetrate the superconductor.With zero resistance, there is practically no energy loss via the heating of material when the electrical current flows. The application of superconductors could result in more efficient electrical devices and much faster and powerful computer systems. The superconductor material needs to be cooled to a very low—and hardly obtained—critical temperature to achieve superconductive properties.

Researchers from the Cooperative Institute for Research in Environmental Sciences (CIRES)at the University of Colorado Boulder recently published an paper in Applied Physics Letters about their discovery of a potential new superconductor. The scientists experimented with and made new superconductor material by using an ultrathin layer of rhenium (Re), which is placed between layers of gold (Au) one-thousandth the diameter of a human hair. Significantly, the material becomes a superconductor at a temperature of approximately 6° K, which is higher than the boiling temperature of liquid helium (at approximately 4°K).

Rhenium is an oxidation-resistant metal that has a melting temperature of 3459 K [9]. It is used widely in various industrial and scientific applications, such as for strengthening materials and high-degree Kelvin temperature thermocouples. Rhenium is a generally expensive but is still attractive as a material since it is a refractory metal that is highly suitable for high temperature, energy, and electrical and biomedical applications.

Generally, the biggest issue with otherwise promising research in this area is in the production, which is sometimes very expensive, complicated or difficult to adapt to mass production. In contrast, there are different manufacturing processes for obtaining thin rhenium semiconducting alloy films, such as powder metallurgy, chemical vapor deposition, and partially electroless plating. However, the most promising is an electroplating process that allows an alloy of high purity to be produced. This method enables easily control of the thickness of the material and could be simply scaled for use in mass production. An additional benefit is that it does not require expensive and sophisticated equipment. The different methods are presented and analyzed in the research published in Researchgate: The Electrochemical Deposition of Rhenium Chalcogenides from Different Electrolytes by Elza Salakhova.

Three high-purity forms of rhenium metal: a single crystal (99.999% pure) made by the floating-zone process, an e-beam remelted bar (99.995% pure), and a 1 cm3 cube (99.99% pure) for comparison. (Image courtesy of Alchemist-hp (talk) (www.pse-mendelejew.de.)

The ability to electroplate the material gives this new superconductor great potential for use in the next generation of circuit boards that could result in ultrafast computing devices.

The greatest advantage of rhenium superconductors is superconductivity at a higher critical temperature, which can be achieved more easily, is easy to mechanically process, and uses a nontoxic material. Unlike rhenium, other superconductor materials, such as mercury and lead, are difficult to mechanically process and do not have good soldering properties.

Since its publication, the research garnered interest from both technology giants and government sponsors, providing an excellent confirmation of the potential of rhenium superconductors.