Impact of defects on photoexcited carrier relaxation dynamics in GeSn thin films.

We report the results of a study that was conducted to investigate the recombination paths of photoexcited charge carriers in GeSn thin films. The charge carrier lifetime was predicted as a function of temperature from a description of photoconductivity transients, assuming co-influence of Shockley-Read-Hall and radiative carrier recombination paths. We identify that dislocations are the source of a band of electronic states with the highest occupied state at E V + (85÷90) meV that acts as Shockley-Read-Hall centers determining the charge carrier lifetime. The photoluminescence (PL) and photoconductivity spectroscopy have been applied to distinguish between the contribution of both band-to-band and dislocation-related electron transitions. The PL band was found to demonstrate a low-energy shift of about 80 ± 20 meV relative to the edge of the photoconductivity spectra in the indirect bandgap GeSn films with dislocations. The role of a different nature deeper acceptor level at E V + (140 ÷ 160) meV in the recombination processes of the GeSn layers with better structural quality and the Sn content higher than 4% was discussed. This detailed understanding of the recombination processes is of critical importance for developing GeSn/Ge-based optoelectronic devices.

Magnetic and structural changes in the near-surface epitaxial Y2.95La0.05Fe5O12 films after high-dose ion implantation.

The method of magnetic force microscopy was used to study the domain structure of various-thickness epitaxial Y2.95La0.05Fe5O12 iron-yttrium garnet films modified by high-dose implantation of N+ nitrogen ions. The results of multi-crystal x-ray diffractometry were analyzed, and a possible defect structure of garnets prior to and after implantation was identified. It was established that the reduction of magnetic losses observed after high-dose ion implantation is accompanied by the essential ordering of magnetic domains on the surface of implanted films. There is a direct dependence of electromagnetic properties on the dose of implanted atoms followed by a considerable sputtering and amorphization of the near-surface film layer and formation of a well-defined electromagnetic structure.

[TESTING USING ATOMIC FORCE MICROSCOPY OF ALLOGRAFT INDIVIDUAL COMPATIBILITY WITH RECIPIENT BODY].

The specificity of the test networks for hernia repair using an atomic force microscopy was studied. The method allows to determine the compatibility of allograft material with the body of the patient, and select the appropriate implant support optimal patient after surgery.

Engineering of 3D self-directed quantum dot ordering in multilayer InGaAs/GaAs nanostructures by means of flux gas composition.

Lateral ordering of InGaAs quantum dots on the GaAs (001) surface has been achieved in earlier reports, resembling an anisotropic pattern. In this work, we present a method of breaking the anisotropy of ordered quantum dots (QDs) by changing the growth environment. We show experimentally that using As(2) molecules instead of As(4) as a background flux is efficient in controlling the diffusion of distant Ga adatoms to make it possible to produce isotropic ordering of InGaAs QDs over GaAs (001). The control of the lateral ordering of QDs under As(2) flux has enabled us to improve their optical properties. Our results are consistent with reported experimental and theoretical data for structure and diffusion on the GaAs surface.