Nanostructuring of the surface of Bi2Te3 epitaxial films during ion-plasma treatment

Abstract

The effect of ion plasma treatment on the surface morphology and optical properties of Bi2Te3 epitaxial films has been studied. Bismuth telluride films were grown by molecular beam epitaxy on (111)BaF2 substrates and had a thickness of 290nm. Ion-plasma treatment of the film surface was carried out in a high-density argon plasma reactor with a high-frequency induction discharge (13.56MHz) and low pressure. The energy of Ar+ ions was set in the range of 25−150eV, the duration of treatment was in the range of 10−120s. 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 13−40nm. From the optical transmission spectra, the value of the band gap Eg =0.87−1.29eV for nanostructured Bi2Te3 systems was determined. The obtained Eg values are several times higher than the values for bulk bismuth telluride (∼ 0.16eV), which can be explained by the implementation of quantum size effects.