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High-temperature growth of ultra thin NbTiN films on lithium niobate for integrated single photon detection

Sjoerd Telkamp1,2,*, Odiel Hooybergs1,3,2,*, Myriam Rihani3,2, Giovanni Finco3,2, Tummas Napoleon Arge3,2, Robin N. Dürr4, Victor Mougel4, Daniel Scheffler5, Filip Krizek5 et al.

Rachel Grange3,2, Robert J. Chapman3,2, and Werner Wegscheider1,2

  • 1Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
  • 2Quantum Center, ETH Zurich, CH-8093 Zurich, Switzerland
  • 3Optical Nanomaterials Group, Institute for Quantum Electronics, ETH Zurich, CH-8093 Zurich, Switzerland
  • 4Department of Chemistry and Applied Biosciences, ETH Zurich, CH-8093 Zurich, Switzerland
  • 5Institute of Physics, Czech Academy of Sciences, 162 00 Prague, Czech Republic

  • *These authors contributed equally to this work.
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Phys. Rev. Materials 10, 066202 – Published 22 June, 2026

DOI: https://doi.org/10.1103/r4xx-y1qj

Abstract

Lithium niobate-on-insulator (LNOI) is an emerging photonic platform with high potential for scalable quantum information processing due to its strong second-order nonlinearity. However, little progress has been made in developing on-chip single-photon detectors on LNOI. Niobium titanium nitride (NbTiN) superconducting nanowire single-photon detectors (SNSPDs) are a promising candidate for this application. In this work, we use DC reactive magnetron sputtering to grow high-quality NbTiN thin films using an ultrahigh vacuum deposition system with a base pressure lower than 2×10−10 mbar. Enabled by the low concentration of background impurities in this system, we investigate the impact of substrate temperature during NbTiN growth. We achieve four nm thick superconducting films with a critical temperature (Tc) of 12.3 K grown at a substrate temperature of 825 K. We find that the NbTiN films grow in the (111) orientation and evolve from a porous pillar structure when grown at low temperatures to densely packed fibrous grains at higher temperatures. Furthermore, we demonstrate that the increased substrate temperature reduces the oxygen concentration in our films and improves the overall stoichiometry. In addition, we integrate these films with the LNOI platform and investigate the obtained interface quality. Lastly, we fabricate SNSPDs from the NbTiN film on LNOI and characterize the detector performance.

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Phys. Rev. Materials 10, 066202– Published 22 June, 2026
  • Received 22 September 2025
  • Accepted 25 March 2026
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