Multi-layer graphene and graphite nanoflakes were produced through graphite liquid exfoliation using organic solvents. The nanoflakes size distribution was statistically analyzed, with the number of ...measured samples being high enough (from ∼200 to 900) for reliable evaluation of the statistical model. The nanoflakes size data were found to follow a log-normal distribution, with higher fraction of large size flakes as compared to a conventional normal distribution. The same kind of distribution was also obtained for nanoflakes thickness. Based on these findings, the detailed mechanism of the pristine polycrystalline graphite exfoliation in a liquid phase due to formation and collapse of cavitation bubbles was discussed. The high quality of nanoflakes was confirmed by Raman spectroscopy.
•Ferromagnetic (Ga,Mn)As layers were obtained by pulsed laser deposition and annealing.•Results of X-ray diffraction, TEM and the magnetization study are presented.•Decomposition of MnAs inclusions ...is observed after laser annealing of thin (Ga,Mn)As layer.•The Curie temperature increased to 105–110 K in the annealed thin (Ga,Mn)As layer.
We have investigated the layers of the (Ga,Mn)As diluted magnetic semiconductor with the thickness in the range of 150 – 400 nm, which have been formed by the combination of the methods of a pulsed laser deposition and a post-growth pulsed laser annealing. It has been found that the laser annealing has a significant effect on the structural, magnetic, and electrical properties of the thinnest (∼150 nm) (Ga,Mn)As layer. For this layer the additional activation of the Mn impurity, the Curie temperature increase and the dissolution of the second phase MnAs clusters have been observed. The results of model calculations of heat spread in (Ga,Mn)As layer have shown that in thicker layers a MnAs melting point temperature is not achievable (for the chosen conditions of pulsed laser annealing) in the entire layer.
This article deals with the formation of coalitions for sustainable development and sustainable finance in developed countries and in Russia. In developed countries, broad national coalitions for ...sustainable development have been formed based on the initially established industry coalitions of investors and financial institutions for sustainable finance. The ideological core of such coalitions is the idea of new models of capitalism based on the principles of sustainable development as an ideal social structure. The concepts of stakeholder capitalism and the impact or caring economy are examples of such models. In Russia, similar coalitions are much narrower because of the imitation of following the environmental, social, and governance (ESG) principles and mass greenwashing. At the same time, there are objective factors that can lead to the expansion of ESG coalitions and strengthening incentives for the implementation of a sustainable development model in Russia.
The possibility of using implantation of 20-keV He
+
ions for modification of the domain structure and magnetic properties of CoPt films (formed by the electron-beam evaporation method) with ...different cobalt contents (Co
0.45
Pt
0.55
and Co
0.35
Pt
0.65
) has been investigated. A decrease in the coercive field (narrowing of the hysteresis loop in the magnetic-field dependences of the Faraday angle and magnetization) with an increase in the He
+
ion fluence from 2 × 10
14
to 4 × 10
14
cm
–2
has been found for the irradiated CoPt samples of both compositions. The residual magnetization of the Co
0.35
Pt
0.65
films coincides with the saturation magnetization, and a decrease in the residual magnetization is observed for Co
0.45
Pt
0.55
. It is shown by magnetic force microscopy that the largest number of round isolated domains (skyrmions) for the Co
0.45
Pt
0.55
alloy are formed when the ion fluence increases to 3 × 10
14
cm
–2
, while 360-degree domain walls (1D skyrmions) are observed along with round isolated domains for the Co
0.35
Pt
0.65
films irradiated with a He
+
fluence of 4 × 10
14
cm
–2
. An analysis of CoPt films by Mandelstam–Brillouin spectroscopy revealed an increase in the shift between the Stokes and anti-Stokes components of the spectrum and a significant enhancement of the Dzyaloshinski–Moriya interaction in the irradiated samples. Model calculations performed using the SRIM program showed that the ion irradiation facilitates asymmetric mixing of Co and Pt atoms in CoPt films, which may underlie the mechanism of the observed effects of ion irradiation on their magnetic properties and domain structure.
The possibility of modifying the properties of a (Ga,Mn)As layer on the surface of a quantum-size InGaAs/GaAs-structure by laser annealing with the conservation of its emitting properties is studied. ...To perform these studies by a combination of the methods of MOC-hydride epitaxy and pulsed laser deposition, the structures have been prepared with four quantum wells InGaAs/GaAs (indium contents from 0.08 to 0.25) located at various distances from the (Ga,Mn)As layer. The radiation energy density of an LPX-200 pulsed excimer laser was varied during the experiments from 200 to 360 mJ/cm
2
, and the depth of the laser action was determined from the changes in the photoluminescence spectra of the quantum wells. The results are described using the laser annealing model based on the solution of the problem of heat propagation in a one-dimensional GaAs system, taking into account a (Ga,Mn)As layer on the surface. The changes in the structural and galvanomagnetic properties of the samples under action of laser irradiation are analyzed. It is shown that the pulsed laser irradiation with the laser radiation energy density 250–300 mJ/cm
2
enable one to conserve the emitting properties of the active region (quantum wells InGaAs/GaAs) disposed at the distances 10–12 nm from the (Ga,Mn)As layer and to modify the ferromagnetic properties of the (Ga,Mn)As semiconductor, namely, to increase the ferromagnet–paramagnet phase transition temperature to values no lower than 120 K. The results are promising for the development of the technology of devices of spin optoelectronics.
GaAs diodes for TiT2-based betavoltaic cells Dorokhin, M.V.; Vikhrova, O.V.; Demina, P.B. ...
Applied radiation and isotopes,
January 2022, 2022-01-00, 20220101, Volume:
179
Journal Article
Peer reviewed
The GaAs semiconductor structures for the application as betavoltaic power sources were investigated. Three types of structures underwent a comparative study: a Schottky diode, a p-n junction and ...Schottky structure modified by deposition of a carbon layer. The power characteristics were estimated by Monte-Carlo simulation and collected current calculation using parameters obtained from the electron beam induced current technique. It was shown that carbon deposition on the top of n-GaAs allows passivating the surface states and thus improving betavoltaic performance.
•The GaAs diode part of TiT2-based betavoltaic cell was developed.•Thin carbon layer on the top of GaAs allowed improving the performance.•Characteristics of power supplies were estimated using the Monte-Carlo simulation.
Using a combination of MOC-hydride epitaxy and pulsed laser deposition, InGaAs/GaAs heteronanostructures with a (Ga,Mn)As layer on the surface are obtained, and the influence of the action of a ...pulsed excimer laser (with a wavelength of 248 nm, pulse duration of ~30 ns, and energy density in the range of 200–360 mJ/cm
2
) on their radiative, structural, and galvanomagnetic properties is studied. The study is carried out using photoluminescence spectroscopy complemented by the possibility of analyzing radiation polarization characteristics of the structures. The crystalline perfection of the initial and laser-irradiated samples was studied with the use of Raman scattering spectroscopy. The elementary composition of the structures and its distribution over the depth were studied by secondary ion mass spectrometry. The influence of pulsed laser annealing on ferromagnetic properties of heteronanostructures is characterized by the behavior of magnetic field dependences of the Hall resistance and magnetoresistance at temperatures of 10–300 K within the range of magnetic fields of ±3600 Oe. At room temperature, the study was carried out in magnetic fields reaching ±28 000 Oe. The calculated temperature distributions along the sample thickness and in time using the laser annealing model based on solving the problem about heat propagation in a one-dimensional GaAs system with allowance for the (Ga,Mn)As layer on the surface are obtained using original data on the thermal conductivity of structures with a (Ga,Mn)As layer. The data were obtained by the modified frequency division technique (the 3ω method).
The possibilities of doping carbon layers grown by pulsed laser deposition with transition-metal impurities are analyzed. The composition and optical and electrical parameters of structures on GaAs ...and Si/SiO
2
substrates are studied. It is shown that the introduction of such atoms as Fe ones modifies the magnetic properties of layers, which are responsible for nonlinear magnetic-field dependences of the Hall effect at temperatures of up to 300 K.
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