Infoscience

Journal article

Low-temperature indium-bonded alkali vapor cell for chip-scale atomic clocks

A low-temperature sealing technique for micro-fabricated alkali vapor cells for chip-scale atomic clock applications is developed and evaluated. A thin-film indium bonding technique was used for sealing the cells at temperatures of <= 140 degrees C. These sealing temperatures are much lower than those reported for other approaches, and make the technique highly interesting for future micro-fabricated cells, using anti-relaxation wall coatings. Optical and microwave spectroscopy performed on first indium-bonded cells without wall coatings are used to evaluate the cleanliness of the process as well as a potential leak rate of the cells. Both measurements confirm a stable pressure inside the cell and therefore an excellent hermeticity of the indium bonding. The double-resonance measurements performed over several months show an upper limit for the leak rate of 1.5 x 10(-13) mbar.l/s. This is in agreement with additional leak-rate measurements using a membrane deflection method on indium-bonded test structures. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4789942]

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