"Nanocomposites and nanomaterials"

Comparative investigation of bulk and nanolayered properties of perspective TlInS2 ferroelectric
T. Babuka1, K.E. Glukhov1, L.Yu. Kharkhalis1, O.O. Gomonnai2, M. Makowska-Janusik3
1 Institute for Physics and Chemistry of Solid State, Uzhhorod National University, 54 Voloshin St., 88000 Uzhhorod, Ukraine
E-mail: tanya.babuka@gmail.com
2 Uzhhorod National University, 46 Pidhirna Str., 88000 Uzhhorod, Ukraine
3 Institute of Physics, Faculty of Mathematics and Natural Science, Jan Dlugosz University in Czestochowa, Al. Armii Krajowej 13/15, 42-200 Czestochowa, Poland

Nanomaterials occupy one of the leading places in searching for new promising materials suitable for functional electronics and alternative energy sources. Triple thallium chalcogenides with a strongly anisotropic structure in the form of tightly bonded layer packages separated by weakly van der Waals interacted gaps, are favorable for the formation of the wide variety of nanostructures for different applications [1]. Therefore, at the stage of searching for new materials that would be characterized by predictable and controlled physical properties, we propose to investigate the evolution of electronic properties of TlInS2 material depending on its thickness (the number of monolayers). 
Physical properties of the TlInS2 crystal in nanolayered form have been investigated theoretically using the DFT method augmented by Hubbard correction are reported and the obtained results are compared to the bulk material parameters. The dependences of electronic and optical properties of the modeled material versus its thin-film thickness were simulated. The significant influence of the TlInS2 slab thickness on its bandgap value was found. In addition, the absorption edge shifts as a function of layers number giving the absorption peak at the position below a value of bandgap were shown. It's worth noting that the magnitude of the spontaneous polarization of the TlInS2 crystal was calculated for the first time. The firstly proposed structure of the low-temperature ferroelectric phase was treated within the Berry phase formalism, allowing to estimate the electronic and ionic dipole moments for this and all here investigated structures. 
1.	Guler, I., Gasanly, N.   Structural and optical properties of thermally annealed thallium indium disulfide thin films // Thin Solid Films.-2020.-704.-p.137985.