Materials with a small superconducting energy gap are expected to favor a high detection efficiency of low-energy photons in superconducting nanowire single-photon detectors. We developed a TaN detector with smaller gap and lower density of states at the Fermi energy than in comparable NbN devices, while other relevant parameters remain essentially unchanged. The observed reduction of the minimum photon energy required for direct detection is in line with model predictions of ≈ 1/3 as compared to NbN.

Ultra-thin films of superconducting tantalum nitride are deposited by reactive magnetron sputtering on heated sapphire substrates. The critical temperature T C=10.25 K is reached for films thicker than 10 nm. A superconducting nanowire single-photon detector in the form of a meander line with a width of 110 nm was made from 5 nm thick TaN film. The detector had a transition temperature of 8.3 K and a critical current density of 4 MA/cm2 at 4.2 K. A photon detection efficiency of 20% has been obtained for the detector with a filling factor of 0.55 at wavelengths up to 700 nm.

Several recent theoretical dosimetric studies above 6 GHz apply generic layered skin models. For this frequency range, new experimental phantoms for over‐the‐air performance of wireless devices were proposed that simulate the impedance matching effects of the stratum corneum layer (SCL) with a low‐loss coating layer. The aim of this study was to verify the skin models by comparing their reflection coefficients S11 with measurements of 37 human volunteers (21 males, 16 females, 5–80 years) at 21 body locations (10 at palm, 11 at arm/face) with different SCL thicknesses, using waveguides covering frequencies from 40 to 110 GHz. Such measurements were also carried out with the phantom material. The statistical analysis showed strong evidence that S11 depends on the SCL thickness and no evidence that S11 depends on sex. The measured S11 values for thin and thick skin can be represented by SCL layers of 15 and 140 μm, respectively. These values correspond well to the assumptions of previous studies. (The cohort did not include volunteers doing heavy manual work.) The phantom material mimics the matching effect of the SCL with deviations from the waveguide measurements of less than 0.85 dB (22%), which confirms the suitability of layered phantoms to represent the electromagnetic reflection/absorption of human skin. © 2021 Bioelectromagnetics Society.