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Heterogeneous integration of NbTiN by universal room temperature deposition
KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics. (Quantum Nano Photonics)ORCID iD: 0000-0003-1831-2208
(Quantum Nano Photonics)
KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics. (Quantum Nano Photonics)
KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics. (Quantum Nano Photonics)
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Being the Nb-based compound with the highest known critical temperature, NbTiN is of particular interest for many applications. It is used in Josephson junctions for single flux quantum logic gates, as a superconducting electrode to contact semiconductor devices, and one important use is in superconducting nanowire single photon detectors. These detectors are the ideal candidate for on-chip integration in photonic circuits, offering near-unity detection efficiency, low noise and excellent time resolution, therefore it is desirable to implement them on a wide variety of platforms. However, it remains a challenge to deposit the superconducting material with a process suitable for heterogeneous integration, as the most widespread material, NbN, is associated with a deposition at a high temperature. Taking advantage of the possibility to deposit superconducting NbTiN with various stoichiometries by co-sputter deposition at room temperature, we demonstrate growth on six different substrates – silicon dioxide, silicon nitride, gallium arsenide, lithium niobate, [Pb(Mg1/3Nb2/3)O3]-x[PbTiO3] or PMN-PT, and aluminum nitride – in the same deposition run, and show that all the films exhibit superconducting properties with similar critical temperatures. We fabricated waveguide-compatible superconducting nanowire single photon detectors on five substrates, report short dead times for all devices with a narrow spread of performances, and discuss their different photon detection saturation behavior. Our method simplifies the fabrication of superconducting devices on a wide range of materials.

National Category
Condensed Matter Physics
Identifiers
URN: urn:nbn:se:kth:diva-251751OAI: oai:DiVA.org:kth-251751DiVA, id: diva2:1316864
Note

QC 20190521

Available from: 2019-05-21 Created: 2019-05-21 Last updated: 2019-05-21Bibliographically approved
In thesis
1. NbTiN for improved superconducting detectors
Open this publication in new window or tab >>NbTiN for improved superconducting detectors
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The physics of single photons is fascinating, by manipulating them we can observe and probe quantum effects. Doing so requires the fabrication and utilization of single photon sources, of which many types have been developed including quantum dots, trapped atoms and ions, and color centers. On the other end of the experiments, single photon detectors play a role of utmost importance, and while several types of detectors exist, superconducting nanowire single photon detectors are now the state-of-the-art technology. By offering near unity detection efficiency from the ultra-violet to the mid-infrared light spectrum, with negligible noise and excellent time resolution, they made possible many experiments that were previously technologically unfeasible. The same appealing characteristics have found a use in applications outside of the quantum optics framework, with notably light detection and ranging, biomedical imaging or CMOS circuits testing.In this thesis a controlled growth method for tailoring the characteristics of niobium titanium nitride in the framework of superconducting nanowire single photon detectors was developed. Reactive co-sputter deposition of niobium titanium nitride was shown to be a versatile method, both in terms of the degree of control over the material composition, and in the choice of substrates that it allows. Unity internal detection efficiency of detectors at telecom wavelengths was achieved by optimizing the niobium content in the material. The influence of lattice matching on the critical temperatures of films deposited at room temperature was investigated. The fabrication of superconducting nanowire single photon detectors on aluminum nitride-on-sapphire, on lithium niobate nano-waveguides, on gallium arsenide, and the integration on SiN waveguides was achieved. The material was used to fabricate detectors with optimized response for any linear polarization of the incoming photons by using a fractal architecture. Another method was proposed to achieve the same results by encapsulating meandering detectors in a high index dielectric material, resulting in a decrease of the permittivity mismatch between the nanowire material and its surrounding and therefore optimizing the efficiency for both orthogonal linear polarizations.Finally, detectors were fabricated from films developed in this work, and were operated to enable the implementation of polarization-based entanglement distribution in optical fibers in a real-conditions scenario, over a record distance of 96 km. This paves the way for the development of quantum communication networks using existing optical fiber links.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2019. p. iii-xviii, 66
Series
TRITA-SCI-GRU ; 2019:34
Keywords
superconducting nanowire sngle photon detector, SNSPD, niobium titanium nitride, NbTiN, reactive co-sputtering, quantum communications, quantum sensing
National Category
Condensed Matter Physics
Research subject
Physics
Identifiers
urn:nbn:se:kth:diva-251759 (URN)978-91-7873-192-3 (ISBN)
Public defence
2019-06-14, FB42, Roslagstullbacken 21, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
EU, European Research Council, 307687Swedish Research Council, 638-2013-7152
Note

QC 20190521

Available from: 2019-05-21 Created: 2019-05-21 Last updated: 2019-05-22Bibliographically approved

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Gyger, SamuelLettner, ThomasErrando-Herranz, CarlosJöns, Klaus D.Zwiller, Val

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