Research Area – Sensorics and Spectrometry
Research Area: Sensorics
Major research activities in sensorics concern the development of high-Tc Josephson junctions and superconducting quantum interferometer devices (dc-SQUIDs) based on epitaxial YBaCuO films. The Josephson junctions are mainly bicrystal and used for Hilbert spectroscopy (single junction sensors) as well as for dc-SQUIDs (two junction sensors such as the one displayed in the picture on the right). The development of dc-SQUIDs also includes the development of epitaxial superconducting multilayer flux transformers based on YBaCuO, PrBaCuO, SrTiO, and BaZrO perovskite films.
Dc-SQUIDs designed and fabricated by PGI-5 are used as very sensitive magnetic field sensors. In combination with a superconducting multilayer flux transformer, PGI-5 has achieved a record magnetic field resolution of approximately 4 fT/sqrt(Hz) at 77 K. By constructing an electronic gradiometer comprising of two such magnetometers, a gradient resolution of about 1 fT/cm sqrt(Hz) at 77 K has been achieved. High-Tc dc-SQUID sensors from PGI-5 have been made available to internal and external clients since 1995 and used, for example, in biomagnetic and geomagnetic sensing, or in non-destructive evaluations as well as in the study of elementary particles and materials science.
The highest quality of epitaxial growth in multilayer perovskite heterostructures is vital to ensure the low noise performance of the sensors. This is strongly connected with further development work taking place in deposition technology (sputtering machines) and microscopic methods (HRTEM) at PGI-5..
Research Area: Spectrometry
PGI-5, in collaboration with the Kotelnikov Institute of Radio Engineering & Electronics of RAS is active in developing Josephson detectors and spectroscopic applications of the ac Josephson effect to fill a spectral gap between microwave and infrared ranges. Two types of spectroscopy are under study, namely, admittance spectroscopy and Hilbert spectroscopy, based on a modification of the dc I-V curve of a Josephson junction by external environment and external radiation, respectively. These spectroscopies may possess a unique combination of broad spectral span, high dynamic power range and fast electrically-driven scanning.
The development of special types of junctions, which should demonstrate Josephson oscillations with the narrowest line width and the broadest voltage-controlled frequency span, is a great challenge in this field. Due to the high energy gap of high-Tc superconductors, these materials have been chosen for junction development and, due to their small coherence lengths, only high-Tc grain-boundaries are considered for the development of high-quality artificial junctions. An improvement of cation ordering and oxygen content at the grain-boundary region plus its impact on nonlinear static and dynamic characteristics of the high-Tc Josephson junctions are among the main goals of our research.
Admittance spectroscopy investigates, for example, spectral losses in the junction environment associated with oxygen mobility in the grain boundary, optical phonon modes in high-Tc superconducting electrodes, substrate resonant modes, and antennas integrated within the junction, to name but a few of the possible applications.. Further development of admittance spectroscopy to the stage where it might be applied to any external sample in the junction environment, is one of the great challenges facing research scientists in this area today.
Spectra of various cw and pulsed radiation sources within frequencies ranging from a few GHz to a few THz are studied using Hilbert spectroscopy. Using radiation sources with continuous and polychromatic spectra, Hilbert spectroscopy may be utilised for the spectroscopic study of solid-state, liquid and gas samples in applications where a high dynamic power range and high-speed measurements are required. A promising application of Hilbert spectroscopy presently under study is the identification of bottled liquids in security systems, where both the speed and reliability of measurements are of great importance.