Improvement of the critical temperature of NbTiN films on III-nitride substrates

Machhadani, H.; Zichi, Julien; Bougerol, Catherine; Lequien, S.; Thomassin, Jean-Luc; Mollard, Nicolas; Mukhtarova, Anna; Zwiller, Val; Gérard, Jean‐Michel; Monroy, E.

doi:10.1088/1361-6668/aaf99d

Cited by 15 publications

(10 citation statements)

References 34 publications

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“…We also note that there is no temperature range where the Arrhenius plot reveals linear behavior over an extended temperature range, indicating that there is no well-defined activation energy. Interestingly, figure 3 structures, strain, and alloying [18,19,30,31]. Growth of Aucatalyzed SiGe NWs on polycrystalline NbTiN could facilitate the interdiffusion of atoms (e.g.…”

Section: Resultsmentioning

confidence: 99%

Direct growth of crystalline SiGe nanowires on superconducting NbTiN thin films

Wang

Thomas²,

Baldwin³

et al. 2023

Nanotechnology

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Novel heterostructures created by coupling one-dimensional semiconductor nanowires with a superconducting thin film show great potential toward next-generation quantum computing. Here, by growing high-crystalline SiGe nanowires on a NbTiN thin film, the resulting heterostructure exhibits Ohmic characteristics as well as a shift of the superconducting transition temperature (Tc). The structure was characterized at atomic resolution showing a sharp SiGe/NbTiN interface without atomic interdiffusion. Lattice spacing, as calculated from large-area X-ray diffraction experiments, suggests an out-of-plane compressive strain within the NbTiN films upon growth of SiGe nanowires, which explains the downward shift of the superconductivity behavior. The present results provide scientific insights into heterostructure coupling from multi-dimensions showing tunable of superconducting properties that provide benefits for quantum science application.

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Section: Resultsmentioning

confidence: 99%

Direct growth of crystalline SiGe nanowires on superconducting NbTiN thin films

Wang

Thomas²,

Baldwin³

et al. 2023

Nanotechnology

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“…Employing single-crystal NbN films could reduce the variation in device performance of SNSPDs. Recently, AlN was proposed as a substrate for the epitaxial growth of NbN films. − The distance between Nb (or N) atoms on the (111) plane of rock-salt-type NbN is 0.310 nm, which is close to the a -axis lattice constant of AlN (0.3112 nm). This small lattice mismatch facilitates the growth of high-quality NbN films on AlN substrates.…”

Section: Introductionmentioning

confidence: 90%

Reduction of Twin Boundary in NbN Films Grown on Annealed AlN

Kihira

Kobayashi

Ueno

et al. 2022

Crystal Growth & Design

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Superconducting nanowire single-photon detectors (SNSPDs) based on ultrathin niobium nitride (NbN) films have attracted much attention owing to their high superconducting transition temperature and fast response time. AlN is a suitable substrate for obtaining high-quality single-crystal NbN films because of the small lattice mismatch between them. However, NbN(111) grown on AlN(0001) suffers from the formation of high-density twin boundaries. In this study, we reduce the NbN twin boundaries using atomically flat AlN substrates annealed at 1700 °C. The twin-boundary-free region of the NbN grown on the annealed AlN is extended to ∼1 × 1 μm2. The epitaxial growth elucidated in this study may contribute to the fabrication of large-area NbN/AlN SNSPDs without structural defects.

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“…However, NbN is generally deposited on amorphous or highly-mismatched substrates, which leads to polycrystalline structure with degraded critical temperature and film inhomogeneities that limit the fabrication yield and reproducibility of SNSPDs. In order to improve the crystalline quality of NbN, low-mismatch substrates such as sapphire, TiN, MgO, SiC, GaN, Nb 5 N 6 or AlN [29,30,38,[45][46][47][48][49][50] have been proposed, but they are not well-suited for large-scale applications compared to silicon. On the other hand, the beneficial effects of a sputtered AlN buffer layer have been demonstrated in the case of using quartz [51] or GaAs [52] as carrier wafer.…”

Section: Introductionmentioning

confidence: 99%

Improvement of critical temperature of niobium nitride deposited on 8-inch silicon wafers thanks to an AlN buffer layer

Rhazi¹,

Machhadani²,

Bougerol³

et al. 2021

Supercond. Sci. Technol.

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In this paper, we study the crystalline properties and superconducting critical temperature of ultra-thin (5–9 nm) NbN films deposited on 8-inch silicon wafers by reactive sputtering. We show that the deposition of NbN on a thin (10–20 nm) AlN buffer layer, also synthesized by reactive sputtering, improves the critical temperature by several Kelvin, up to 10 K for 9 nm NbN on 20 nm AlN. We correlate this improvement to the higher-crystalline quality of NbN on AlN. While NbN deposited directly on silicon is polycrystalline with randomly oriented grains, NbN on AlN(0001) is textured along (111), due to the close lattice match. The superconducting properties of the NbN/AlN stack are validated by the demonstration of fibre-coupled normal-incidence superconducting nanowire single photon detectors. The whole fabrication process is CMOS compatible, with a thermal budget compatible with the integration of other passive and active components on silicon. These results pave the way for the integration of a large number of surface or waveguide-integrated detectors on large-scale silicon wafers. Furthermore, as AlN is transparent over a broad wavelength range from the visible to the near-infrared, the optimized superconducting NbN/AlN stack can be used for a wide variety of applications, from imaging to quantum communications and quantum computing.

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Improvement of the critical temperature of NbTiN films on III-nitride substrates

Cited by 15 publications

References 34 publications

Direct growth of crystalline SiGe nanowires on superconducting NbTiN thin films

Direct growth of crystalline SiGe nanowires on superconducting NbTiN thin films

Reduction of Twin Boundary in NbN Films Grown on Annealed AlN

Improvement of critical temperature of niobium nitride deposited on 8-inch silicon wafers thanks to an AlN buffer layer

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