Efficiency of macro- and micronutrients in spring wheat protection system

The work presents studies of preparative laboratory forms of preparations containing nanoparticles of macro- and micronutrients by inclusion of stabilizers and solution modifiers on growth and development of spring triticale plants in the first phases of ontogenesis and spring wheat under field conditions. The preparations and their rates positively affecting germination energy, germination rate with the effect of 4-6% and plant growth under the influence of preparations on daily seedlings were isolated in laboratory studies. The preparations Mn, 10 ml/t, Ca, 10 ml/t, Mo, 50 ml/t, Titan M, 50 ml/t, biogenic Fe, 5 ml/t had a positive effect on energy and germination, while the preparations Mn, 10 ml/t, Ca, 10 ml/t, Mo, 50 ml/t, Titan M, 50 ml/t, biogenic Fe, 5 ml/t, Bor 5 mg/g + GC (10%) had a positive effect on sprout length, 1ml/t, Potassium, 1000 ml/t of which the variants with Boron 5 mg/g + GC (10%), 1ml/t, Potassium, 1000 ml/t had the greatest and significant effect, where the increase in sprout length was 1.0-3.2 cm or 7.8-25%, mass 0.5-1.4 g or 6-8%. In field studies, we evaluated the use of biogenic iron in the plant protection system as a stimulant in the treatment of seeds together with a seed dressing and plants during the growing season. The effect of the preparation on the development of plants contributing to increased yield was determined, especially the treatment of wheat plants in the earing phase, which provided an increase of 0.5 t/ha.

Morphology, Structure, and Optical Properties of Semiconductor Films with GeSiSn Nanoislands and Strained Layers

The dependences of the two-dimensional to three-dimensional growth (2D-3D) critical transition thickness on the composition for GeSiSn films with a fixed Ge content and Sn content from 0 to 16% at the growth temperature of 150 °С have been obtained. The phase diagrams of the superstructure change during the epitaxial growth of Sn on Si and on Ge(100) have been built. Using the phase diagram data, it becomes possible to identify the Sn cover on the Si surface and to control the Sn segregation on the superstructure observed on the reflection high-energy electron diffraction (RHEED) pattern. The multilayer structures with the GeSiSn pseudomorphic layers and island array of a density up to 1.8 × 10¹² cm^-2 have been grown with the considering of the Sn segregation suppression by the decrease of GeSiSn and Si growth temperature. The double-domain (10 × 1) superstructure related to the presence of Sn on the surface was first observed in the multilayer periodic structures during Si growth on the GeSiSn layer. The periodical GeSiSn/Si structures demonstrated the photoluminescence in the range of 0.6-0.85 eV corresponding to the wavelength range of 1.45-2 μm. The calculation of the band diagram for the structure with the pseudomorphic Ge_0.315Si_0.65Sn_0.035 layers allows assuming that photoluminescence peaks correspond to the interband transitions between the X valley in Si or the Δ₄-valley in GeSiSn and the subband of heavy holes in the GeSiSn layer.

Influence of delta-doping on the hole capture probability in Ge/Si quantum dot mid-infrared photodetectors

We study the effect of delta-doping on the hole capture probability in ten-period p-type Ge quantum dot photodetectors. The boron concentration in the delta-doping layers is varied by either passivation of a sample in a hydrogen plasma or by direct doping during the molecular beam epitaxy. The devices with a lower doping density is found to exhibit a lower capture probability and a higher photoconductive gain. The most pronounced change in the trapping characteristics upon doping is observed at a negative bias polarity when the photoexcited holes move toward the δ-doping plane. The latter result implies that the δ-doping layers are directly involved in the processes of hole capture by the quantum dots.

Photovoltaic Ge/Si quantum dot detectors operating in the mid-wave atmospheric window (3 to 5 μm)

: Ge/Si quantum dots fabricated by molecular-beam epitaxy at 500°C are overgrown with Si at different temperatures Tcap, and effect of boron delta doping of Si barriers on the mid-infrared photoresponse was investigated. The photocurrent maximum shifts from 2.3 to 3.9 μm with increasing Tcapfrom 300°C to 750°C. Within the sample set, we examined devices with different positions of the δ-doping layer with respect to the dot plane, different distances between the δ-doping layer and the dot plane d, and different doping densities pB. All detectors show pronounced photovoltaic behavior implying the presence of an internal inversion asymmetry due to the placing dopants in the barriers. The best performance was achieved for the device with Tcap = 600°C, pB = 12 × 1011cm-2, and d = 5 nm in a photovoltaic regime. At a sample temperature of 90 K and no applied bias, a responsivity of 0.83 mA/W and detectivity of 8 × 1010 cm Hz1/2/W at λ = 3.4 μm were measured under normal incidence infrared radiation.

Formation of Ge-Sn nanodots on Si(100) surfaces by molecular beam epitaxy

The surface morphology of Ge0.96Sn0.04/Si(100) heterostructures grown at temperatures from 250 to 450°C by atomic force microscopy (AFM) and scanning tunnel microscopy (STM) ex situ has been studied. The statistical data for the density of Ge0.96Sn0.04 nanodots (ND) depending on their lateral size have been obtained. Maximum density of ND (6 × 1011 cm-2) with the average lateral size of 7 nm can be obtained at 250°C. Relying on the reflection of high energy electron diffraction, AFM, and STM, it is concluded that molecular beam growth of Ge1-xSnx heterostructures with the small concentrations of Sn in the range of substrate temperatures from 250 to 450°C follows the Stranski-Krastanow mechanism. Based on the technique of recording diffractometry of high energy electrons during the process of epitaxy, the wetting layer thickness of Ge0.96Sn0.04 films is found to depend on the temperature of the substrate.