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Emelianov, A. V., Nekrasov, N. P., Moskotin, M. V., Fedorov, G. E., Otero, N., Romero, P. M., et al. (2021). Individual SWCNT transistor with photosensitive planar junction induced by two‐photon oxidation. Adv. Electron. Mater., 7(3), 2000872.
Abstract: The fabrication of planar junctions in carbon nanomaterials is a promising way to increase the optical sensitivity of optoelectronic nanometer-scale devices in photonic connections, sensors, and photovoltaics. Utilizing a unique lithography approach based on direct femtosecond laser processing, a fast and easy technique for modification of single-walled carbon nanotube (SWCNT) optoelectronic properties through localized two-photon oxidation is developed. It results in a novel approach of quasimetallic to semiconducting nanotube conversion so that metal/semiconductor planar junction is formed via local laser patterning. The fabricated planar junction in the field-effect transistors based on individual SWCNT drastically increases the photoresponse of such devices. The broadband photoresponsivity of the two-photon oxidized structures reaches the value of 2 × 107 A W−1 per single SWCNT at 1 V bias voltage. The SWCNT-based transistors with induced metal/semiconductor planar junction can be applied to detect extremely small light intensities with high spatial resolution in photovoltaics, integrated circuits, and telecommunication applications.
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Samsonova, A., Zolotov, P., Baeva, E., Lomakin, A., Titova, N., Kardakova, A., et al. (2021). Signatures of surface magnetic disorder in thin niobium films. IEEE Trans. Appl. Supercond., , 1.
Abstract: We present our studies on the evolution of the normal and superconducting properties with thickness of thin Nb films with a low level of non-magnetic disorder (kFl 150 for the thickest film in the set). The analysis of the superconducting behavior points to the presence of magnetic moments, hidden in the native oxide on the surface of Nb films. Using the Abrikosov-Gorkov theory, we obtain the density of surface magnetic moments of 1013 cm-2, which is in agreement with the previously reported data for Nb films.
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Baeva, E. M., Titova, N. A., Veyrat, L., Sacépé, B., Semenov, A. V., Goltsman, G. N., et al. (2021). Thermal relaxation in metal films bottlenecked by diffuson lattice excitations of amorphous substrates. arXiv:2101.07071v1 [cond-mat.mtrl-sci]. Retrieved May 15, 2024, from https://arxiv.org/abs/2101.07071v1
Abstract: Here we examine the role of the amorphous insulating substrate in the thermal relaxation in thin NbN, InOx, and Au/Ni films at temperatures above 5 K. The studied samples are made up of metal bridges on an amorphous insulating layer lying on or suspended above a crystalline substrate. Noise thermometry was used to measure the electron temperature Te of the films as a function of Joule power per unit of area P2D. In all samples, we observe the dependence P2D∝Tne with the exponent n≃2, which is inconsistent with both electron-phonon coupling and Kapitza thermal resistance. In suspended samples, the functional dependence of P2D(Te) on the length of the amorphous insulating layer is consistent with the linear T-dependence of the thermal conductivity, which is related to lattice excitations (diffusons) for the phonon mean free path smaller than the dominant phonon wavelength. Our findings are important for understanding the operation of devices embedded in amorphous dielectrics.
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Baksheeva, K., Ozhegov, R., Goltsman, G., Kinev, N., Koshelets, V., Kochnev, A., et al. (2021). The sub THz emission of the human body under physiological stress. IEEE Trans. Terahertz Sci. Technol., .
Abstract: We present evidence that in the sub-THz frequency band, human skin can be considered as an electromagnetic bio-metamaterial, in that its natural emission is a product of skin tissue geometry and embedded structures. Radiometry was performed on 32 human subjects from 480 to 700 GHz. Concurrently, the subjects were exposed to stress, while heart pulse rate (PS) and galvanic skin response (GSR) were also measured. The results are substantially different from the expected black body radiation signal of the skin surface. PS and GSR correlate to the emissivity. Using a simulation model for the skin, we find that the sweat duct is a critical element. The simulated frequency spectra qualitatively match the measured emission spectra and show that our sub-THz emission is modulated by our level of mental stress. This opens avenues for the remote monitoring of the human state.
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Goltsman, G. N. (2021). Development and applications of terahertz hot electron bolometers. In 1st Moscow Int. Conf. on Submillimeter and Millimeter Astronomy: Objectives and Instruments.
Abstract: The development of techniques and technologies for the deposition of ultrathin superconducting films, the creation of superconducting structures on a nanometer scale is the basis of significant progress in the field of superconducting receiving systems. Ultrathin NbN films are the basis for a wide range of record-breaking hot electron devices: direct and heterodyne terahertz detectors. Terahertz receivers are especially in demand in high-resolution spectroscopy for astronomical, atmospheric, and medical research. HEB receivers are widely used in terahertz radio astronomy. For example, the Dutch SRON Institute is preparing a project for the GUSTO hot air balloon telescope with a HEB mixer array at 1.4 THz and 1.9 THz. A 5-meter Chinese terahertz telescope DATE5 with HEB mixers at 1.4 THz is installed at the South Pole. The Stratospheric Observatory (SOFIA) uses HEB mixer matrices in the GREAT instrument operating in the 1.2 – 4.7 THz range. It is planned to implement the international project Origins Space Telescope (OST) in the far infrared region based on HEB receivers. The Japanese project Smiles-2 will allow measurements at 1.8 THz in the upper layers of the stratosphere and mesosphere. The development of the Millimetron space observatory continues in Russia.
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