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GaInP microdisks contained InP/GaInP quantum dots having lateral size ∼150 nm and 1-5 μm−2 were investigated with help of microphotoluminescence technique. Experiments carried out in confocal, time-resolved and low-temperature modes. Comparison of results allowed to conclude that overlap of quantum dot emission area with whispering gallery mode antinode results in faster luminescence lifetime (Purcell effect). Whispering gallery mode lasing was detected. Obtained threshold power values were following 6 µW (Q=4500, T=8.5 K) and 0.4 µW (Q=7400, T=80 K).

In this work, we demonstrate the possibility of using local anodic oxidation (LAO) for fabricating optical devices based on thin transition metal dichalcogenides (TMDC) layers. By LAO we fabricated an optical cavity from 6-layered MoSe2 flake transferred on Si/Au substrate. Optical properties were investigated by measuring microphotoluminescence. The cavity exhibits three order of magnitude enhancement of the flake's photoluminescence, which is only one order of magnitude lower than the monolayer on a SiO2 substrate. Here we show that LAO is a high-precision lithography method suitable for fabricating optoelectronic devices made of thin TMDC layers.

Multilayer (Ni/ZrO2)45 nanostructures are obtained by the simultaneous sputtering of two Ni and ZrO2 targets and the deposition of material on moving substrates. The multilayer nature of the obtained samples was confirmed by small-angle X-ray reflectometry. It has been established that with a change in the thickness of nickel layers (from 1.5 to 10.8 nm), their morphology changes from discrete to continuous. A change in the morphology of nickel layers radically changes the electrical and magnetoresistive properties of multilayer nanostructures. Magnetoresistive effect is observed in the multilayer structures with discreet nickel layers.

We study the optical properties of MoS2 nanotubes (NTs) with walls comprising dozens of monolayers. We reveal strong peaks in micro-photoluminescence (l-PL) spectra when detecting the light polarized along the NT axis. We develop a model describing the optical properties of the nanotubes acting as optical resonators which support the quantization of whispering gallery modes inside the NT wall. The experimental observation of the resonances in l-PL allows one to use them as a contactless method of the estimation of the wall width. Our findings open a way to use such NTs as polarization-sensitive components of nanophotonic devices.

We report on co-doping of high-quality AlN single crystals by group II Beryllium acceptors by means of diffusion from the vapour phase at a temperature of 1850 °C. We discovered that Be is characterized by the high diffusion length, allowing one to produce Be co-doping of sub-mm-thick AlN wafers. We show that Be diffusion led to the quenching of the visible (VIS) 450 nm (2.75 eV) and deep ultraviolet (UV) 265 nm (4.7 eV) optical absorption bands with simultaneous induction of the absorption band peaked at 248 nm (5 eV). By means of electron paramagnetic resonance (EPR), we also found that the presence of Be impurities compensated the donor type paramagnetic centers. Correlation of the EPR data with the optical absorption allowed us to conclude that Be produced in the AlN via diffusion acted predominantly as an acceptor, inducing the shift of the Fermi level to the lower part of the AlN bandgap. This shift of the Fermi level results in recharging of the deep level defects in the AlN bandgap, which explains the observed quenching of the VIS and UV absorption bands.

We study structural and chemical transformations induced by focused laser beam in GaAs nanowires with axial zinc-blende/wurtzite (ZB/WZ) heterostucture. The experiments are performed using a combination of transmission electron microscopy, energy-dispersive X-ray spectroscopy, Raman scattering, and photoluminescence spectroscopy. For the both components of heterostructure, laser irradiation under atmospheric air is found to produce a double surface layer which is composed of crystalline arsenic and of amorphous GaO$_{x}$. The latter compound is responsible for appearance of a peak at 1.76 eV in photoluminescence spectra of GaAs nanowires. Under increased laser power density, due to sample heating, evaporation of the surface crystalline arsenic and formation of $\beta$-Ga$_{2}$O$_{3}$ nanocrystals proceed on surface of the zinc-blende part of nanowire. The formed nanocrystals reveal a photoluminescence band in visible range of 1.7-2.4 eV. At the same power density for wurtzite part of the nanowire, total amorphization with formation of $\beta$-Ga$_{2}$O$_{3}$ nanocrystals occurs. Observed transformation of WZ-GaAs to $\beta$-Ga$_{2}$O$_{3}$ nanocrystals presents an available way for creation of axial and radial heterostuctures ZB-GaAs/$\beta$-Ga$_{2}$O$_{3}$ for optoelectronic and photonic applications., Comment: 12 pages, 5 figures

The effect of biaxial strain on optical phonons in high-quality GaN epitaxial layers grown on 6H–SiC substrates by metal organic chemical vapor deposition has been studied. The deformation potential constants for the E2(1), A1(TO), E1(TO), and E2(2) optical phonon modes in hexagonal GaN have been obtained. A method for calculating strain in hexagonal GaN layers from Raman data alone is suggested. A comparative analysis of the strain measured by x-ray diffraction and Raman spectroscopy shows that these data agree well. It is found that the biaxial stress of 1 GPa results in a shift of the excitonic photoluminescence lines of 20±3 meV.

The vibrational spectra of group 12 difluorides, MF2 (M = Zn, Cd, Hg), were investigated via coupled cluster singles, doubles, and perturbative triples, CCSD(T), including core correlation, with a series of correlation consistent basis sets ranging in size from triple-zeta through quintuple-zeta quality, which were then extrapolated to the complete basis set (CBS) limit using a variety of extrapolation procedures. The explicitly correlated coupled cluster method, CCSD(T)-F12b, was employed as well. Although exhibiting quite different convergence behavior, the F12b method yielded the CBS limit estimates closely matching more computationally expensive conventional CBS extrapolations. The convergence with respect to basis set size was examined for the contributions entering into composite vibrational spectroscopy, including those from higher-order correlation accounted for through the CCSDT(Q) level of theory, second-order spin-orbit coupling effects assessed within four-component and two-component relativistic formalisms, and vibrational anharmonicity evaluated via a perturbative treatment. Overall, the composite results are in excellent agreement with available experimental values, except for the CdF2 bond-stretching frequencies compared to spectral assignments proposed in a matrix isolation infrared and Raman study of cadmium difluoride vapor species [Loewenschuss et al., J. Chem. Phys. 50, 2502 (1969); Givan and Loewenschuss, J. Chem. Phys. 72, 3809 (1980)]. These assignments are called into question in the light of the composite results.

We propose to use a Tornado-type closed magnetic trap for creation of a source of multicharged ions with plasma heating by microwave radiation. Plasma loss in closed traps is determined by diffusion across the magnetic field, which increases substantially plasma confinement time as compared to the classical mirror trap. The Tornado trap also possesses merits such as: an opportunity to produce high magnetic fields up to 3 T, which makes possible heating and confinement of plasma with a high density of electrons; an opportunity to use supplementary coils for ion extraction; plasma stability to magnetohydrodynamic perturbations because the magnetic field structure corresponds to the “min B” configuration; and relatively low costs. All estimates and calculations were carried out for the existing Tornado-322 pulse installation (maximal magnetic field 2.8 T) with plasma heating at 53 GHz frequency. The numerical simulation has shown that, by the end of the magnetic field pulse, ion distribution over charge stat...

The first- and second-order Raman scattering and IR reflection have been studied for hexagonal InN layers grown on (0001) and (1102) sapphire substrates. All six Raman-active optical phonons were observed and assigned: E2(low) at 87 cm−1, E2(high) at 488 cm−1, A1(TO) at 447 cm−1, E1(TO) at 476 cm−1, A1(LO) at 586 cm−1, and E1(LO) at 593 cm−1. The ratio between the InN static dielectric constants for the ordinary and extraordinary directions was found to be e⊥0/e∥0=0.91. The phonon dispersion curves, phonon density-of-state function, and lattice specific heat were calculated. The Debye temperature at 0 K for hexagonal InN was estimated to be 370 K.

Raman studies of Mg-doped InN films with a Mg content from NMg=3.3×1019to5.5×1021cm−3 are reported. Raman and secondary ion mass spectroscopy data on the Mg content have been found to correlate well. Lattice dynamics of hexagonal InN with substitutional impurities and vacancies has been investigated in the framework of the cluster approach. Energy positions of local vibrational modes in InN have been calculated and compared with experimental findings. It is concluded that Raman spectroscopy is a good tool for quantitative characterization of Mg-doped InN.