Design and Characterisation of Titanium Nitride Subarrays of Kinetic Inductance Detectors for Passive Terahertz Imaging

Abstract

We report on the investigation of titanium nitride (TiN) thin films deposited via atomic layer deposition (ALD) for microwave kinetic inductance detectors (MKID). Using our in-house ALD process, we have grown a sequence of TiN thin films (thickness 15, 30, 60 nm). The films have been characterised in terms of superconducting transition temperature , sheet resistance and microstructure. We have fabricated test resonator structures and characterised them at a temperature of 300 mK. At 350 GHz, we report an optical noise equivalent power , which is promising for passive terahertz imaging applications.

Applications for Microwave Kinetic Induction Detectors in Advanced Instrumentation

“…MKIDs are a promising technology for these applications because they allow large arrays of detectors due to their multiplexabiliy, with time responses of ~ 10 −4 s, while detecting frequencies from about 300 to 1000 GHz (1.0-0.3 mm), at which certain materials which are opaque at optical wavelengths become transparent. While active THz imaging is already used in airports around the world for security screening, MKIDs would, due to their improved sensitivity, allow for passive THz imaging with fast time responses, allowing for subjects to be scanned while simply walking past the camera, greatly reducing the time needed for each traveler to be screened [148][149][150][151][152]. Doyle et al in Cardiff University have developed a passive 350 GHz (860 µm) fieldscanning LEKID camera [148], operating at a "quasi-video" frame rate of 2 Hz, and noise equivalent temperature of ~0.1 K per frame based on a linear array of 152 LEKIDs.…”

“…Morozov et al [149] in Glasgow have investigated the use of atomic layer deposition (ALD) to deposit titanium nitride (TiN) thin films, for use in MKIDs for passive THz imaging. TiN thin films were the material of choice due to their greater than 300mK critical temperatures, allowing the use of compact cryogenic systems, reducing the overall complexity of the system.…”

High-uniformity atomic layer deposition of superconducting niobium nitride thin films for quantum photonic integration

“…This process, known as the 'ALD cycle' , can then be repeated until a desired thickness is attained, enabling Ångstrom-level thickness control [2] ALD is therefore highly uniform, conformal and scalable, with the deposition area being limited by the size of the reaction chamber [3,4]. Consequently, there has been significant interest from the superconducting device community, where uniform, pinhole-free films are a necessity for applications such as superconducting nanowire single-photon detectors (SNSPDs), microwave kinetic inductance detectors (MKIDs), superconducting resonators, superconducting qubits and superconducting through-silicon vias [5][6][7][8][9]. For MKIDs and SNSPDs in particular, large area uniformity is essential for scaling up to large area arrays and cameras [10].…”