2015-11 RFSiB4

2015-11 RFSiB4Edit

Left resonator (122 nm thickness), run 2015-11-28

No hint of SiB. Al has weird behavior (don't understand the multiple resonances seen, it may be a problem with fabrication)

Middle resonator (68 nm thickness), run 2015-12-11

Now the line is measured with an isolator + filter between sample and amplifier -> no more ripples
But still we can see nothing appearing / moving below 200mK. The resonances appear below 1.2K, which is pathological (not designed). Either SiB turns superconducting at 1.2K, or the Aluminium layer has a problem (discontinuities, not matched 50ohm, or else)

Comparison of the results of the 2 resonators: (one common feature at 9GHz -> probably extrinsic: ?bondings? ?box resonance?)

For comparison, below, a similar design of lambda/2 resonator in NbSi (except the Lk is much larger, so for the same frequency, resonator is much shorter), with Tc 900mK, Al ground plane, same measurement setup (even lighter, as there was no isolator nor filter!). (+ the resonator was there coupled to a gate on the side). Fundamental is 3.5GHz. "Troubles" (unsimulated features) appear only above 9GHz.