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Experimental evidence of a very thin superconducting layer in epitaxial indium nitride
摘要： Indium nitride is one of the very few semiconductors which is known to have a superconducting phase at temperatures of Tc > 1 K. Superconductivity occurs in a window of carrier densities of approximately 1018–1020 cm?3. This is a very low density when compared to other superconductors (i.e. metals, alloys, high Tc oxides) and thus raises interesting fundamental questions as well as technological possibilities. In this paper we address one key question about the dimensionality of the superconducting state of InN by using angle dependent critical field measurements. Our samples were grown by two different growth techniques (chemical vapour deposition and plasma-assisted molecular beam epitaxy) on c-oriented sapphire, with and without a GaN buffer layer. In both cases we find that for film thicknesses much larger than the coherence length d ? ξ, the angle dependence of the critical field (down to T < 280 mK) with respect to the c-axis continues to be clearly two-dimensional, demonstrating a characteristic cusp when the angle crosses 90° with respect to the c-axis. This indicates that the superconducting electrons are most likely confined to a layer much thinner than the thickness of the InN film. Further we find the magnitude of the gap to be 2Δ(0)/kBTc = 3.6, very close to the BCS prediction.
关键词： indium nitride,penetration depth,angle dependent critical field,coherence length,critical current,superconductivity
更新于2025-09-09 09:28:46
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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Penetration Depth Evaluation of Split Ring Resonator sensor using In-Vivo Microwave Reflectivity and Ultrasound Measurements
摘要： This article focuses on the application of split ring resonator based sensor for follow up recovery of lower extremity trauma patients. The proposed sensor mainly monitors the changes of dielectric properties of lower limb tissues such as skin, fat, muscle and bone. As part of the characterization of microwave sensor, it is crucial to assess the signal penetration in in-vivo tissues. This work presents a new approach for investigating the penetration depth of Split Ring Resonator sensor in in-vivo context of the femoral area. The method is based on the measurement of skin, fat, and muscle tissue thicknesses from ultrasound images. The microwave reflectivity, S11 measurements are done in conjunction with ultrasound measurements on four volunteers to deduce the effective permittivity of the in-vivo tissues. The tissue thickness information derived from ultrasound measurements were used to create 3D simulation model in CST studio 2017. The measured S11 values are used to optimize the effective permittivity of that model. The penetration depths are calculated from the simulation of electric field distribution in the optimized model. The analysis on measured data shows that the thigh region contributes highest penetration depth up to 17.5mm. This result has higher significance in demonstrating the in-vitro penetration depth measurements and other tests which are going to be performed in the future.
关键词： Microwave,Ultrasound,Sensor,Penetration depth,Split Ring Resonator
更新于2025-09-04 15:30:14