Surface physics, thin films

Nanostructuring of the surface of Bi$_2$Te$_3$ epitaxial films during ion-plasma treatment

S. P. Zimin^ab, I. I. Amirov^a, V. V. Naumov^a, M. S. Tivanov^c, L. S. Lyashenko^b, O. V. Korolek^c, E. Abramof^d, P. H. O. Rappl<sup>d

a</sup> Yaroslavl branch of the Institute of physics and technology, Institution of Russian academy of sciences, Yaroslavl, Russia
^b P.G. Demidov Yaroslavl State University, Yaroslavl, Russia
^c Belarusian State University, Minsk, Republic of Belarus
^d Materials and plasma research and development group (GPDMP), National Institute for Space Research (INPE), São José dos Campos, 12227-010, Brazil

Abstract: The effect of ion plasma treatment on the surface morphology and optical properties of Bi$_2$Te$_3$ epitaxial films has been studied. Bismuth telluride films were grown by molecular beam epitaxy on (111)BaF$_2$ substrates and had a thickness of 290 nm. Ion-plasma treatment of the film surface was carried out in a high-density argon plasma reactor with a high-frequency induction discharge (13.56 MHz) and low pressure. The energy of Ar$^+$ ions was set in the range of 25–150 eV, the duration of treatment was in the range of 10–120 s. Effective nanostructuring of the surface of bismuth telluride was discovered, leading to the appearance of nanostructures of various shapes and architectures with geometric sizes of 13–40 nm. From the optical transmission spectra, the value of the band gap $E_g$ = 0.87–1.29 eV for nanostructured Bi$_2$Te$_3$ systems was determined. The obtained $E_g$ values are several times higher than the values for bulk bismuth telluride ($\sim$0.16 eV), which can be explained by the implementation of quantum size effects.

Keywords: bismuth telluride, epitaxial films, ion-plasma treatment, nanostructures, Raman scattering, reflection and transmission spectra.

Received: 20.05.2024
Revised: 06.06.2024
Accepted: 10.06.2024

DOI: 10.61011/FTT.2024.08.58608.131