Erratum: Effects of alloy disorder and confinement on phonon modes and Raman scattering in SixGe1-x nanocrystals: A microscopic modeling

Erratum: “Effects of alloy disorder and confinement on phonon modes and Raman scattering in SixGe1-x nanocrystals: A microscopic modeling” [J. Appl. Phys. 115, 143505 (2014)].info:eu-repo/semantics/publishedVersio

Effects of alloy disorder and confinement on phonon modes and Raman scattering in SixGe1-x nanocrystals : a microscopic modeling

Confinement and alloy disorder effects on the lattice dynamics and Raman scattering in Si1-xGex nanocrystals (NCs) are investigated numerically employing two different empirical inter-atomic potentials. Relaxed NCs of different composition (x) were built using the Molecular Dynamics method and applying rigid boundary conditions mimicking the effect of surrounding matrix. The resulting variation of bond lengths with x was checked against Vegard's law and the NC phonon modes were calculated using the same inter-atomic potential. The localization of the principal Raman-active (Si-Si, Si-Ge and Ge-Ge) modes is investigated by analysing representative eigenvectors and their inverse participation ratio. The dependence of the position and intensity of these modes upon x and NC size is presented and compared to previous calculated results and available experimental data. In particular, it is argued that the composition dependence of the intensity of the Si-Ge and Ge-Ge modes does not follow the fraction of the corresponding nearest-neighbour bonds as it was suggested by some authors. Possible effects of alloy segregation are considered by comparing the calculated properties of random and clustered SixGe1-x NCs. It is found that the Si- Si mode and Ge-Ge modes are enhanced and blue-shifted (by several cm-1for the Si-Si mode), while the intensity of the Si-Ge Raman mode is strongly suppressed by clustering.Portuguese Foundation or Science and Technology (FCT) and FEDER through Projects PTDC-FIS-113199-2009 and PEst-C/FIS/UI0607/201

Optically controlled spin-polarization memory effect on Mn delta-doped heterostrucutres

We investigated the dynamics of the interaction between spin-polarized photo-created carriers and Mn ions on InGaAs/GaAs:Mn structures. The carriers are confined in an InGaAs quantum well and the Mn ions come from a Mn delta-layer grown at the GaAs barrier close to the well. Even though the carriers and the Mn ions are spatially separated, the interaction between them is demonstrated by time-resolved spin-polarized photoluminescence measurements. Using a pre-pulse laser excitation with an opposite circular-polarization clearly reduces the polarization degree of the quantum-well emission for samples where a strong magnetic interaction is observed. The results demonstrate that the Mn ions act as a spin-memory that can be optically controlled by the polarization of the photocreated carriers. On the other hand, the spin-polarized Mn ions also affect the spin-polarization of the subsequently created carriers as observed by their spin relaxation time. These effects fade away with increasing time delays between the pulses as well as with increasing temperatures.Comment: 12 pages, 5 figure

Acceleration of the precession frequency for optically-oriented electron spins in ferromagnetic/semiconductor hybrids

Time-resolved Kerr rotation measurements were performed in InGaAs/GaAs quantum wells nearby a doped Mn delta layer. Our magneto-optical results show a typical time evolution of the optically-oriented electron spin in the quantum well. Surprisingly, this is strongly affected by the Mn spins, resulting in an increase of the spin precession frequency in time. This increase is attributed to the variation in the effective magnetic field induced by the dynamical relaxation of the Mn spins. Two processes are observed during electron spin precession: a quasi-instantaneous alignment of the Mn spins with photo-excited holes, followed by a slow alignment of Mn spins with the external transverse magnetic field. The first process leads to an equilibrium state imprinted in the initial precession frequency, which depends on pump power, while the second process promotes a linear frequency increase, with acceleration depending on temperature and external magnetic field. This observation yields new information about exchange process dynamics and on the possibility of constructing spin memories, which can rapidly respond to light while retaining information for a longer period.Comment: 7 pages, 5 figure

Reduction of technogenic impact on the soil by increasing the stability of road trains movement within the field

The outcomes of assessing the possibility of reducing the technogenic impact on the soil during field operations in crop production are presented by increasing the stability of the transport movement and technological means in agricultural fields. An increase in the number of passes, a distortion of the tramline shape, an increase in slippage, wobbling and sliding of technical equipment on the field lead to a significant deterioration in the topography and structure of the soil layer, which causes soil destruction and a decrease in its productivity. Transport work performed on agricultural fields leads to a significant negative technogenic impact on the soil due to the numerous passes, large transported weight, and the application of trailers. The impact on the stability of the road trains movement is considered in the paper. Characteristics of damped oscillations are used to evaluate the efficiency of impacts on stability. The method of changing the inclination angle of the turntable kingpin of the road train trailer is chosen by the method of influencing the movement stability. It is established that changing the inclination angle of the turntable kingpin of the road train trailer allows reducing the average amplitude of oscillations of the trailer front side by 26.5-28%, increasing the period of oscillations by 33.3%, and also slightly changing the decrement of oscillations by 0.5-2.5%. Therefore, structural changes in the towing device of vehicles, by providing better directional stability, will reduce the technogenic load on the soil: decrease compaction and destruction of the soil layer. © 2023 Institute of Physics Publishing. All rights reserved.This research was funded by the Indonesian Research Center of Marine and Fisheries Product Processing and Biotechnology. The authors thank Umi Anissah, Ajeng Kurniasari Putri, and Fairdiana Andayani for their assistance in sampling fresh Bombay ducks