Atomic layer deposition of titanium nitride for quantum circuits

Abstract

Superconducting thin films with high intrinsic kinetic inductance are of great importance for photon detectors, achieving strong coupling in hybrid systems, and protected qubits. We report on the performance of titanium nitride resonators, patterned on thin films (9-110 nm) grown by atomic layer deposition, with sheet inductances of up to 234 pH/ . For films thicker than 14 nm, quality factors measured in the quantum regime range from 0.4 to 1.0 million and are likely limited by dielectric two-level systems. Additionally, we show characteristic impedances up to 28 kΩ, with no significant degradation of the internal quality factor as the impedance increases. These high impedances correspond to an increased single photon coupling strength of 24 times compared to a 50 Ω resonator, transformative for hybrid quantum systems and quantum sensing.

Implementation of a Transmon Qubit Using Superconducting Granular Aluminum

“…Granular aluminum, similarly to other materials such as NbN [21], NbTiN [22], or TiN [23], is an attractive choice for superconducting hybrid systems operating at radio frequencies, due to its large critical magnetic field [24,25], high coherence in the microwave domain [26][27][28][29], and intrinsic nonlinearity [30,31]. The constituent Al grains, about 3-5 nm in diameter [32], are separated by thin oxygen barriers; therefore, grAl structures can be modeled as arrays of JJs [30].…”

Cryogenic characterization of titanium nitride thin films

“…Needless to say that the sudden drop of ε 2 below 4 K comes from the drop of ω p (T) as discussed above. Another tempting, seemingly plausible explanation could be using the known fact of the superconducting phase transition in thin TiN films at T<1 K [17,18] as a factor to drastically affect the low-T electron plasma oscillation frequency. However, the superconducting coherence length of Cooper pairs does not typically exceed a few nanometers, which is a too tiny scale to be able to affect the long-wavelength plasmon dispersion and the plasmon coherence length on the order of a micrometer (let alone the fact of T c being much less than 4 K at which we start seeing the effect here).…”

“…It has been shown previously that the permittivity of TiN films of variable thickness is greatly dependent on temperature and fabrication methods [14,15], however, only the range above 20 • C was analyzed in the temperature-dependent studies. Moreover, aside from the dc conductivity measurements for superconductor applications [16][17][18], no studies of the dielectric response function and its plasmonic implications at low temperatures were reported so far to the best of our knowledge.…”

Fluxonium Steps up to the Plate

“…It is important to realize that the effective loss tangent of the inductance must be in the 10 −7 -10 −8 range in order to reach the coherence times reported in this experiment. Whether such a low loss can be reached with dirty superconductors is an interesting question [52][53][54][55][56]. Our specific Josephson tunnel junction chain design [ Fig.…”