Celesta S. Chang

High-Q superconducting microwave resonators using MBE titanium nitride

  1. Anand Ithepalli,
  2. Haoran Lu,
  3. Eegene Clara Chung,
  4. Xiangqin Wang,
  5. Amit Rohan Rajapurohita,
  6. Keun-Yeol Park,
  7. Celesta S. Chang,
  8. Peter McMahon,
  9. Huili Grace Xing,
  10. David Muller,
  11. Valla Fatemi,
  12. and Debdeep Jena
Using molecular beam epitaxy, we have realized thin films of titanium nitride (TiN) on c-plane sapphire that exhibit the lowest observed full-width at half maximum X-ray rocking curve
width of 18 arcsec. Though the (111) oriented TiN exhibits an abrupt and crystalline interface with sapphire, for the first time we observe sub-surface defects in the sapphire substrate, which nucleate structural defects in the epitaxial TiN layer. Using quarter-wavelength coplanar waveguide (CPW) resonators in a 3 \textmu m/6 \textmu m/3 \textmu m gap/strip/gap lines in a hanger geometry, we find the internal quality factor of the TiN resonators to be >106 in the single-photon ⟨n⟩∼1 limit at 5.8 GHz and 10 mK, rising to >20×106 at ⟨n⟩∼106. The results are of high interest for applications of superconducting TiN in several areas, and provide a path towards epitaxial Josephson junctions with crystalline barriers in the future for high coherence qubits.
arxiv pdf