Researchers at NIST have developed tiny chip-scale refrigerators that can cool large objects to extremely low temperatures. The refrigerators, each about 25 by 15 micrometers in size, are made of layers of normal metal, insulator, and superconducting metal. When a voltage is applied, the hottest electrons tunnel through the insulator to the superconductor, causing the temperature in the normal metal to drop dramatically.
The researchers used four pairs of these tiny refrigerators to cool a silicon nitride membrane and a cube of germanium, which were about 11,000 times larger than the combined volume of the refrigerators. Both objects were cooled down to about 200 milliKelvin. The refrigerators are fabricated using common chip-making lithography methods, making production and integration with other microscale devices straightforward.
These tiny refrigerators have potential applications in cooling cryogenic sensors for semiconductor defect analysis and astronomical research. The work was supported in part by NASA and NIST’s Office of Microelectronics Programs.
Source: https://www.nist.gov/news-events/news/2005/04/chip-scale-refrigerators-cool-bulk-objects
Keywords: Refrigeration, Cryogenic sensors, Electron-tunneling, Superconducting metal, Semiconductor
