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Semiconductor Industry Uses Colorful Diamonds to Measure Magnetic Fields in Semiconductors
While they may be flawed due to their color, colorful diamonds are among the most sensitive detectors of magnetic fields. University of California, Berkeley, physicist Dmitry Budker, Ron Folman of Ben-Gurion University of the Negev in Israel, and colleagues from UCLA have demonstrated how diamond sensors can measure tiny magnetic fields in high-temperature semiconductors. While high-temperature semiconductors were discovered in the late 1980s, and their discoverers won the Nobel Prize, they are not yet truly understood. “Diamond sensors will give us measurements that will be useful in understanding the physics of high temperature superconductors,” Budker said.
High-temperature semiconductors are mixes of materials like yttrium or bismuth. When cooled to -170 degrees Celsius they loose all resistance to electricity. Low-temperature semiconductors on the other hand have to be chilled to just several degrees above absolute zero. When high-temperature semiconductors were discovered in 1987, it was predicted that room-temperature semiconductors would be a reality in the near future. Room-temperature semiconductors could lead to lossless electrical transmissions or magnetically levitated trains. Neither has yet to be a reality. Colorful diamond sensors could allow researchers to take steps forward to making room-temperature semiconductors a reality.
Colored diamonds range from yellow and orange to even purple. The color comes from flaws in the gem’s carbon structure. Some of the carbon atoms have been replaced by an element, such as boron, that emits or absorbs a specific color of light. After scientists learned that they could create synthetic diamonds, they found they could alter a diamond’s optical properties by injecting impurities. Budker, Folman, and their colleagues bombarded a synthetic diamond with nitrogen atoms to displace some of the carbon atoms, leaving left holes in some places and nitrogen atoms in others. The crystal was then heated, forcing the holes to move and pair with nitrogen atoms, leaving a diamond with a nitrogen vacant center. The amount of light the negatively charged centers re-emit when excited with light becomes sensitive to magnetic fields, allowing them to be used as sensors that are read out by laser spectroscopy. Folman noted that they color centers in diamonds uniquely exhibit quantum behavior, whereas most other solids at room temperature do not. “This is quite surprising, and is part of the reason that these new sensors have such a high potential,” Folman said.
Possible Applications For Colored Diamonds
Researchers hope that nitrogen-vacant centers will be able to probe for cracks in metal, such as bridge structures or jet engine blades, be the building blocks for quantum computers, or even have homeland security applications. Budker works on sensitive magnetic field detectors, and Folman builds atom chips to probe and manipulate atoms, so they have focused on using these magnetometers to study new materials. “These diamond sensors combine high sensitivity with the potential for high spatial resolution, and since they operate at higher temperatures than their competitors – superconducting quantum interference device, or SQUID, magnetometers – they turn out to be good for studying high temperature superconductors,” Budker said. “Although several techniques already exist for magnetic probing of superconducting materials, there is a need for new methods which will offer better performance.” This team of researchers used the diamond sensors to measure properties of a thin layer of yttrium barium copper oxide (YBCO), which is one of the two most popular types of high-temperatures superconductor. The diamond sensor was integrated with the superconductor on one chip and used it to detect the transition from normal conductivity to superconductivity. Tiny magnetic vortices, which appear and disappear as the material becomes superconducting, were also detected.
“Now that we have proved it is possible to probe high-temperatures superconductors, we plan to build more sensitive and higher-resolution sensors on a chip to study the structure of an individual magnetic vortex,” Folman said. “We hope to discover something new that cannot be seen with other technologies.” Researchers are looking into other areas that could benefit from magnetic sending. The possibilities are limitless.
Sanders, Robert. “Colored Diamonds Are a Superconductor’s Best Friend.” UC Berkeley NewsCenter. N.p., 6 Mar. 2014. Web. 17 Apr. 2014.