Nanocomposites and nanomaterials
Spatial confinement effect on the electronic and optical properties of the β-InSe hexagonal crystal

L.Yu. Kharkhalis1, K.E.Glukhov1, T.Ya.Babuka1,2,, M.V Liakh1 

1 Institute of Physics and Chemistry of Solid State, Uzhhorod National University, 
54 Voloshin St., 88000 Uzhhorod, Ukraine, 
E-mail: lkharkhalis@gmail.com

2 Institute of Physics, Faculty of Mathematics and Natural Science, Jan Dlugosz University in Czestochowa, Al. Armii Krajowej 13/15, 42-200 Czestochowa, Poland

Recently, two-dimensional (2D) layered semiconductors of indium selenide keep attracting increasing attention because of their especial layer-dependent physical properties. According to experimental data [1,2] few-layer InSe materials display high electron mobility and blue-shift of photoluminescence peaks that can be exploited for new wide applications in the optoelectronics devices development. In this context, it is of interest to investigate the electronic and optical properties of the slab and bulk β-InSe crystals which show the different peculiarities under spatial confinement influence.
In the present work, we carried out ab initio calculations of the evolution of the electronic and optical properties under transitions from bulk β-InSe layered crystal to its monolayers. We considered the models of one, two and three layers of β-InSe and studied the influence of the number layers on the band structure, the spatial distribution of the electron density and optical characteristics. It is shown that the changes of the band spectrum in the vicinity of the main extrema of the valence band and conduction band are observed. An analysis of the confinement effects on the energy gap has been performed. The spectral dependencies of the real and imaginary parts of the dielectric function and the absorption coefficient have been obtained.  Our calculations suggest a good agreement with results of known experimental investigations. 

1.	Bandurin D. A., Tyurnina A. V., Yu G. L.,  Mishchenko A., et.al. High Electron Mobility, Quantum Hall Effect and Anomalous Optical Response in Atomically Thin InSe// Nature Nanotech.-2017.-. 9.- P. 223-227.
2.	Mudd, G. W., Svatek, S. A.., Ren, T.,  Patanè, A., et.al. Tuning the bandgap of exfoliated InSe nanosheets by quantum confinement// Adv. Mater .- 2013.-  25.- P. 5714-5718.