Randomized trial reveals dielectric functions of tantalum nitride films for tunnel barriers in Josephson junctions, suggesting improved qubit design.
Key Points
This research aims to evaluate the dielectric functions of tantalum nitride films deposited by atomic layer deposition for use as tunnel barriers in Josephson junctions.
Measured temperature-dependent ellipsometric angles for 13 and 25 nm TaN films over photon energy ranges of 0.03–0.7 eV and 0.5–6.5 eV.
Developed a dispersion model using a Tauc–Lorentz oscillator with an optical bandgap of 1.5–1.8 eV.
Conducted transmission electron microscopy and x-ray diffraction analyses.
ALD TaN films demonstrated insulating behavior with mid-infrared transparency at all temperatures tested.
No infrared absorption due to free carriers was observed, confirming their suitability as JJ tunnel barriers.
The N/Ta ratio was found to be ∼1.2, indicating uniform film composition.