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Serhii Shafraniuk

Serhii Shafraniuk

Northwestern University, USA

Title: THz applications of atomic monolayer materials

Biography

Serhii Shafraniuk has completed his PhD from Kiev State University and Postdoctoral studies from Academy of Sciences of Ukraine. He is the Research Associate Professor at Physics and Astronomy Department, Northwestern University, a premier educational and research institution. He has published more than 100 papers in reputed journals and is serving as an organizer of various international conferences.

Abstract

Recent discovery and study of novel atomic monolayer materials has attracted a significant interest in their feasibility for photonics and optoelectronics. It also motivates the efforts of nanotechnology which are directed toward their applications industry, medicine, security, defence, and space research. The recnt tendency in technology of various nanodevices like nanosensors, digital logic elements, quantum dots, THz signal processors and sensors, quantum bits and circuits, etc. is to implement the new materials. Our activity in the aforementioned respect involves the following topics. (i) Quantum dots as elements of the THz and magnetic field nanosensors. (ii) Andreev reflection as a probe of interface properties. (iii) Efficient thermoelectric nanocoolers and energy generators based on atomic monolayer (AM) materials and nanotubes. We implement the AM materials which are represented by graphene and transition metal dichalcogenides. The aim of our work is to exploit the unique intrinsic properties of novel AM materials to design the devices which were not available in the past. In particular, resonant character the chiral tunnelling and low inelastic scattering rates in graphene both are serving as reasons why the electric current density can be much higher than in ordinary semiconducting devices. Another example is Klein tunnelling paradox which makes graphene and nanotubes as being intrinsically "clean" and perspective for electronic applications. Our experimental devices are based on multi-terminal AM field effect transistors (A-FET). An important stage of the A-FET fabrication process assumes obtaining the good quality AM sheets and nanotubes. The obtained quantum dot devices had been used for experimental testing in respect of their performance and suitability for the aforementioned purposes. The A-FET is controlled with source-drain and gate voltages applied via the metallic electrodes deposited on AM. The voltages affect the low energy electronic spectrum and hence they modify the transport properties of AM material. When exposing the A-FET device to an external THz field we have found that the resonant a.c. transport strongly depends on the polarity and magnitude of the source-drain and gate voltages. Besides, the THz field induces transitions between the quantized levels which are pronounced in the experimental current voltage characteristics. By measuring the d.c. current-voltage curves of A-FET quantum dots which are exposed to an external THz field we are able to determine the THz field parameters. In this way we are utilizing the A-FET which actually works as a very sensitive and efficient THz field sensor. Besides we study the thermoelectric cooling and energy co-generating phenomena in AM. We conclude that the AM based setups can perform much better than other known devices.

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