Radiative recombination in BiI₃(Mn) and BiI₃(Cr) layered single crystals

The photoluminescence spectra of BiI₃(Mn) and BiI₃(Cr) single crystals were studied. The new bands at λ = 1.1 and λ = 1.83 μm were registered at the temperature 4.2 K. It was shown that the first and second bands arise due to Mn²⁺ and Cr³⁺ ions, accordingly. The experimental results were explained using the configuration model. The energies between minima of configuration curves of excited and basic states for both centres were estimated

Mechanism of periodic height variations along self-aligned VLS-grown planar nanostructures

In this study we report in-plane nanotracks produced by molecular-beam-epitaxy (MBE) exhibiting lateral self-assembly and unusual periodic and out-of-phase height variations across their growth axes. The nanotracks are synthesized using bismuth segregation on the GaAsBi epitaxial surface, which results in metallic liquid droplets capable of catalyzing GaAsBi nanotrack growth via the vapor–liquid–solid (VLS) mechanism. A detailed examination of the nanotrack morphologies is carried out employing a combination of scanning electron and atomic force microscopy and, based on the findings, a geometric model of nanotrack growth during MBE is developed. Our results indicate diffusion and shadowing effects play significant roles in defining the interesting nanotrack shape. The unique periodicity of our lateral nanotracks originates from a rotating nucleation “hot spot” at the edge of the liquid–solid interface, a feature caused by the relative periodic circling of the non-normal ion beam flux incident on the sample surface, inside the MBE chamber. We point out that such a concept is divergent from current models of crawling mode growth kinetics and conclude that these effects may be utilized in the design and assembly of planar nanostructures with controlled non-monotonous structure

Analysis of exciton reflection spectrum of 2H-PbI₂ layered single crystals with atomically clean surface

We performed the computer modelling of the dispersion dependences of real ε₁(E) and imaginary ε₂(E) parts of complex dielectric function ε(E) for 2H-PbI₂ crystals with atomically clean surface at the temperature 5 K and the light polarization E⊥C and determined the energy position of the exciton bands and the parameters of the critical points. The obtained data allowed us to conclude the exciton spectra of this semiconductor can be described in terms of a single Wannier series with a large ground-state anomaly caused by a repulsive central-cell correction due to the cationic character of the exciton

Influence of Mn and Cr impurities on quasi-surface exciton states of BiI₃ layered single crystals

The influence of Mn and Cr impurities on quasi-surface excitons of BiI3 single crystals was studied. The broadening of their band was found which may be caused by ionization of quasi-surface excitons by the electric field of Mn²+ and Cr³+ ions