Kavli Affiliate: Nathan Lewis
| First 5 Authors: Changsub Kim, Christina Bell, Jake Evans, Jonathan Greenfield, Emma Batson
| Summary:
Progress in superconducting device and detector technologies over the past
decade have realized practical applications in quantum computers, detectors for
far-infrared telescopes, and optical communications. Superconducting thin film
materials, however, have remained largely unchanged, with aluminum still being
the material of choice for superconducting qubits, and niobium compounds for
high frequency/high kinetic inductance devices. Magnesium diboride
($mathrm{MgB}_2$), known for its highest transition temperature
($mathrm{T}_c$ = 39 K) among metallic superconductors, is a viable material
for elevated temperature and higher frequency superconducting devices moving
towards THz frequencies. However, difficulty in synthesizing wafer-scale thin
films have prevented implementation of $mathrm{MgB}_2$ devices into the
application base of superconducting electronics. Here, we report ultra-smooth
(< 0.5 nm root-mean-square roughness) and uniform $mathrm{MgB}_2$ thin (< 100
nm) films over 100 mm in diameter for the first time and present prototype
devices fabricated with these films demonstrating key superconducting
properties including internal quality factor over $mathrm{10}^4$ at 4.5 K and
high tunable kinetic inductance in the order of tens of pH/sq in a 40 nm film.
This groundbreaking advancement will enable development of elevated
temperature, high frequency superconducting quantum circuits and devices.
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