Reduction of helium permeation in microfabricated cells using aluminosilicate glass substrates and Al2O3 coatings

International audienceThe stability and accuracy of atomic devices can be degraded by theevolution of their cell inner atmosphere. Hence,<br /&gtthe undesired entrance or leakage of background or buffer gas,respectively, that can permeate through the cell walls,<br /&gtshould be slowed down. In this work, we investigate heliumpermeation in microfabricated alkali vapor cells filled<br /&gtwith He and whose windows are made of borosilicate glass (BSG) oraluminosilicate glass (ASG). The permeation is<br /&gtthen derived from routine measurements of the pressure-shiftedhyperfine transition frequency of an atomic clock. We<br /&gtfirst confirm that ASG reduces He permeation rate by more than twoorders of magnitude, in comparison with BSG.<br /&gtIn addition, we demonstrate that Al2O3 thin-film coatings, known toavoid alkali consumption in vapor cells, can also<br /&gtsignificantly reduce He permeation. The permeation through BSG isthereby reduced by a factor 110 whereas the one<br /&gtthrough ASG is decreased by a factor up to 5.8 compared to uncoatedsubstrates. These results may contribute to the