The reduction in the area and volume of glaciation in all mountain regions of the Earth has strongly accelerated for the last decades. In this work, we analysed the trends of the main climatic ...parameters which caused the glacier recession in the Kamchatka Peninsula. It was shown that the glaciers of the northern part of the Sredinny Range decreased by 125 km2 (35.6%) from 1950 to 2016–2017. The average rate of their reduction in the period from 2002 to 2016–2017 (1.45%/year) increased approximately 4.3 times compared to the period 1950–2002 (0.34%/year). The greatest reduction is observed in small glaciers with an area of less than 0.1 km2 and in glaciers with southeastern and southern expositions. On the Kronotsky Peninsula, the glacier area reduction for 1957–2019 was equal to 32.1 km2 (35.6%), and the rates were almost the same in the periods of 1957–2000 (0.61%/year) and 2000–2019 (0.67%/year). According to the data of weather stations and ERA5 reanalysis, it was shown that, in the ablation (summer) period the warming rate was minimal (0.3°C/10 years) and in the accumulation period a significant decrease in precipitation (5%–10%/10 years) was revealed in some areas. At the same time, a significant increase in the radiation balance was revealed in the warm season along with a tendency in downward shortwave radiation increase for the last two decades due to a decrease in cloud amount. These trends are in good agreement with the growth of the geopotential height over the North Pacific during the warm season in the 21st century, and with the growth of velocity divergence in the middle troposphere and the intensification of downward air movements. All this confirms an increase in anticyclone frequency in the warm season, which could be the cause of a radiation balance increase and, consequently, an increase in glacier ablation.
Kamchatka glaciers shrank significantly in recent decades: the glacier area of the northern part of the Middle Range (NpMR) and Kronotsky Peninsula (KP) decreased by 35.6% from the middle of the XX century. The most likely reasons for this strong reduction are the winter precipitation decrease and surface radiation balance increase in the warm season (May–September), partly due to the cloud cover decrease, associated with the anticyclone's frequency increase in the North Pacific region at the beginning of the XXI century.
Changes in the structure and elemental composition of the surface of the epitaxy-ready InP(001) substrate in an As flux in ultrahigh vacuum are studied in situ by the reflection high-energy electron ...diffraction (RHEED) technique. It is shown that, during annealing of the oxide layer at the surface, an InP
1 –
x
As
x
layer is formed as a result of the substitution of phosphorus by arsenic. The dependence of the degree of substitution on the annealing temperature and time is established. The degree of the substitution of phosphorus by arsenic in the surface layer is 7% at the annealing temperature 480°C and, reaches 41% at the temperature 540°C. The annealing time influences the degree of substitution only slightly.
Transient photoluminescence (PL) characteristics and localization phenomena in InGaN/GaN core-shell nanorods (NRs) were investigated from 6 K up to 285 K. The NRs exhibit three well-defined PL bands ...in the near-UV, blue, and green range ascribed to the emission of quantum well (QW) areas situated at the (1.00) sidewalls, (10.1) top facets, and (00.1) tip, respectively. At low temperature, time-resolved PL shows a fast decay time of about 0.5 ns for the semi- and non-polar QWs, while the polar QWs exhibit at least a twice-longer time. Rapid delocalization of carriers above 50 K indicates shallow potential fluctuations in the QWs. At room temperature, the characteristic fast PL decay time of the three QW bands stabilizes around 300 ps. The slow decaying PL components have different characteristic decay times that are explained by additional localization at basal stacking faults (BSFs), taking into account the quantum confined Stark effect. In addition, narrow excitonic luminescence lines are observed in the BSF-enriched polar QWs, providing direct evidence of the impact of the BSF/QW crossings on the optical properties of the NRs. A PL rise time of about 100 ps does not show any deviation between bands. These findings are suggestive of similar transport mechanisms in temperature equilibrium without inter-facet transport between different QWs. We believe that predictable transient characteristics can play a key role in creating uniform NR ensembles for device applications.
Transient photoluminescence (PL) characteristics and localization phenomena in InGaN/GaN core-shell nanorods (NRs) were investigated from 6 K up to 285 K.
The results of investigations of the optical characteristics of nonclassical light sources based on selectively positioned microlens structures and single (111) In(Ga)As quantum dots grown on a (111) ...BGaAs substrate are presented. The single-photon nature of the radiation is confirmed by measuring and analyzing second-order correlation functions
g
(2)
(τ);
g
(2)
(0) = 0.07. The fine structure of the exciton states of (111) In(Ga)As quantum dots is investigated. It is shown that, in the energy range of 1.320–1.345 eV, the splitting of exciton states is comparable to the natural width of the exciton lines, which is of interest for developing photon-pair emitters based on them.
The adsorption properties of titanium powders with an effective particle size of 18–32 μm mechanoactivated in a planetary ball mill in a protective atmosphere of n-hexane have been studied at ...different activation times. It has been established that indicators of the specific surface area, Henry’s constant, monolayer capacity, and particle size for activated titanium powders pass through the zones of extreme (min–max) activation values. In this case, the heat of adsorption and the energy of the surface during the adsorption of standard benzene vapor depend on the amount of surface coverage with adsorbed benzene molecules and on the degree of mechanoactivation of the titanium powder. It was found that, at all times of mechanoactivation, the filling of the surface adsorption monolayer has an endothermic sign of the differential molar isosteric heat of adsorption. The reversal of the sign of the heat of adsorption from endothermic to exothermic for all powders corresponds to the completion of the filling of the monolayer and surface nanopores. The observed effect of negativity of the heat of adsorption in the initial region of fillings of the surface of activated titanium powders is explained by the endothermic contribution of the adsorption deformation of the expansion of powder particles with surface nanocracks.
Deterministically integrating semiconductor quantum emitters with plasmonic nano-devices paves the way towards chip-scale integrable, true nanoscale quantum photonic technologies. For this purpose, ...stable and bright semiconductor emitters are needed, which moreover allow for CMOS-compatibility and optical activity in the telecommunication band. Here, we demonstrate strongly enhanced light-matter coupling of single near-surface (< 10 nm) InAs quantum dots monolithically integrated into electromagnetic hot-spots of sub-wavelength sized metal nanoantennas. The antenna strongly enhances the emission intensity of single quantum dots by up to ~ 16×, an effect accompanied by an up to 3.4× Purcell-enhanced spontaneous emission rate. Moreover, the emission is strongly polarised along the antenna axis with degrees of linear polarisation up to ~ 85 %. The results unambiguously demonstrate a pronounced coupling of individual quantum dots to state-of-the-art nanoantennas. Our work provides new perspectives for the realisation of quantum plasmonic sensors, step-changing photovoltaic devices, bright and ultrafast quantum light sources and efficient nano-lasers.
Based on the research work on the use of various alcohols as an alternative motor fuel for various internal combustion engines, a number of conclusions were drawn on the stages of formation of the ...main combustion products. This article presents a part of theoretical studies when using methyl alcohol in the form of a fuel emulsion as an alternative motor fuel. One of the most dangerous toxic components of liquid fuel combustion products is soot. Therefore, it is necessary to find ways to reduce its content. To do this, you need to know the methods and stages of soot formation, which affect the final concentration by weight. The most important task can be called the determination of the prevailing mechanisms of the appearance of soot in the combustion of liquid fuels in the cylinders of engines. A variable zonal model of soot formation in a 4 H 11.0 / 12.5 high-speed diesel engine is presented when working on an alternative emulsified alcohol fuel - methanol-fuel emulsion. The stages of the formation of carbon particles during the oxidation of fuel inside the cylinder are considered.
A biexciton radiative cascade was recorded in the photoluminescence spectra of an InAs/GaAs QD embedded in a λ-cavity with a relatively high-quality factor of 4600, formed in a micropillar with ...GaAs/AlGaAs distributed Bragg reflectors. The spectrum and kinetics of the radiation, measured under conditions of two-photon excitation, demonstrated a significant effect of the microcavity on the emission process. A possible improvement based on this effect in the generation of entangled photon pairs is discussed.
The design and fabrication technology of high-power Schottky-barrier microwave mesa photodiodes from 10 to 40 μm in diameter back-illuminated through the substrate are described. The diodes were made ...on MBE-grown InAlAs/InGaAs/InP heterostructures. The operating frequency of photodiodes 10 μm in diameter has been found to be 40 GHz, and the maximal microwave output at 20 GHz for photodiodes 15 μm in diameter have been found to reach 58 mW. The coefficient of amplitude-to-phase conversion has been determined to be 1.5 rad/W. This value outperforms the available literature data and makes the given design of photodiodes promising for systems of analog microwave signal generation and transmission, which are very sensitive to phase noise.
Abstract
In this work, the process of phosphorus desorption from
epi-ready
InP(001) substrates during high-temperature annealing in an arsenic flux was experimentally investigated. An InPAs solid ...solution and InAs islands were formed on the surface upon annealing. The composition of the solid solution, the surface area fraction occupied by InAs islands, and its height depend on the annealing temperature. The phosphorus desorption rate was determined from the dependence of the arsenic atoms number on the substrate surface on the annealing temperature and the holding time in the arsenic flux. The phosphorus desorption rate increased from 6.03×10
10
s
−1
⋅ cm
−2
at an annealing temperature of 500 °C to 4.38×10
11
s
−1
⋅ cm
−2
at 540 °C. The activation energy of the phosphorus desorption process was 2.7 ± 0.2 eV.
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