| 1. |
- Ivanov, S.V., et al.
(författare)
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MBE growth and properties of bulk BeCdSe alloys and digital (BeSe : CdSe)/ZnSe quantum wells
- 2000
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Ingår i: Journal of Crystal Growth. - 0022-0248 .- 1873-5002. ; 214, s. 109-114
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Tidskriftsartikel (refereegranskat)abstract
- We report for the first time on MBE growth, structural and optical properties of single layers, quantum well structures and short-period superlattices based on BexCd1-xSe ternary alloys on GaAs. Both the conventional MBE growth mode and the sub-monolayer digital alloying technique (SDA) have been employed for the fabrication of the structures. Compositional boundaries of an instability region 0.03 < x < 0.38, calculated in a regular solution approximation for the completely coherent system, agree well with available experimental data. A suppression of the phase separation in BeCdSe by elastic stress in the layer, accompanied by a strong reduction of the Cd incorporation coefficient has been found. Ultrathin 2.8 ML BeCdSe SDA QWs with x approx. 0.15 demonstrate about an order of magnitude increase in the PL intensity with respect to the pure CdSe one, probably resulting from an enhanced carrier localization efficiency. Eg as a function of the Be content reveals a strong bowing in optical data, which allows one to consider BeCdSe alloys with compositions nearly lattice-matched to GaAs as potential materials for the active region of blue-green lasers.
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| 2. |
- Jmerik, V.N., et al.
(författare)
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Optically pumped lasing at 300.4 nm in AlGaN MQW structures grown by plasma-assisted molecular beam epitaxy on c-Al2O3
- 2010
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Ingår i: PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE. - : WILEY-V C H VERLAG GMBH. - 1862-6300. ; 207:6, s. 1313-1317
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Tidskriftsartikel (refereegranskat)abstract
- We have demonstrated optically pumped room-temperature pulse lasing at 300.4 nm from an AlGaN-based multiple-quantum-well (MQW) structure grown by plasma-assisted molecular beam epitaxy on a c-sapphire substrate. The lasing was achieved at the threshold peak power of similar to 12 MW/cm(2). The MQW structure involved AlGaN/AlN short-period super-lattices to decrease the threading dislocation densities from 10(11) down to 10(9)-10(10) cm(-2). Studies of time-resolved photoluminescence (TRPL) spectra and cw PL temperature dependences (10-300K) of different MQW structures, as well as numerical calculations of the optical gain and confinement in the laser structure allowed us to conclude about the optimum design of AlGaN-based MQW structures for the lower threshold UV lasing.
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| 3. |
- Toropov, A.A., et al.
(författare)
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Coexistence of type-I and type-II band lineups in Cd(Te,Se)/ZnSe quantum-dot structures
- 2006
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 89:12
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Tidskriftsartikel (refereegranskat)abstract
- The authors report on transmission electron microscopy, cathodoluminescence, and time resolved photoluminescence studies of thin Cd(Te,Se) layers in a ZnSe matrix, grown by molecular beam epitaxy. All observations confirm strain-induced self-assembly of quantum dots (QD's), induced primarily by the 14% lattice mismatch between CdTe and ZnSe. The emission spectrum of the structure is the superposition of a relatively narrow luminescence line originating from CdSe-enriched type-I QD's and a broad band attributed to the emission of an ultrathin ZnTeSe/ZnSe layer with type-II band lineup, formed in between the QD's. © 2006 American Institute of Physics.
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| 4. |
- Toropov, A. A., et al.
(författare)
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Suppression of the quantum-confined Stark effect in AlxGa1-xN/AlyGa1-yN corrugated quantum wells
- 2013
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Ingår i: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 114:12
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Tidskriftsartikel (refereegranskat)abstract
- We report comparative studies of 6-nm-thick AlxGa1-xN/AlyGa1-yN pyroelectric quantum wells (QWs) grown by plasma-assisted molecular beam epitaxy on c-sapphire substrates with a thick AlN buffer deposited under different growth conditions. The Al-rich growth conditions result in a 2D growth mode and formation of a planar QW, whereas the N-rich conditions lead to a 3D growth mode and formation of a QW corrugated on the size scale of 200-300 nm. Time-resolved photoluminescence (PL) measurements reveal a strong quantum-confined Stark effect in the planar QW, manifested by a long PL lifetime and a red shift of the PL line. In the corrugated QW, the emission line emerges 200 meV higher in energy, the low-temperature PL lifetime is 40 times shorter, and the PL intensity is stronger (similar to 4 times at 4.5K and similar to 60 times at 300 K). The improved emission properties are explained by suppression of the quantum-confined Stark effect due to the reduction of the built-in electric field within the QW planes, which are not normal to the [0001] direction, enhanced carrier localization, and improved efficiency of light extraction.
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| 5. |
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| 6. |
- Shanina, B D, et al.
(författare)
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Magnetism of palladium clusters in nanoporous carbon
- 2009
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Ingår i: Journal of Experimental and Theoretical Physics. - : MAIK Nauka/Interperiodica distributed exclusively by Springer Science+Business Media LLC.. - 1063-7761 .- 1090-6509. ; 109:4, s. 609-18
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Tidskriftsartikel (refereegranskat)abstract
- To determine the electronic properties of metal-carbon clusters, palladium clusters are introduced into nanoporous carbon samples. The structural and magnetic properties of the nanocomposite thus obtained are investigated. A ferromagnetic resonance (FMR) component is observed in the electron spin resonance (ESR) spectra measured in a wide temperature range. The electron density of states (DOS) of clusters consisting of a palladium atom surrounded by carbon atoms is calculated, and it is shown that, due to the interaction between electronic terms of carbon and metal, such a cluster should exhibit magnetism. The investigation of the structures of the porous skeleton of nanoporous carbon and of palladium clusters has allowed us to reveal how carbon and palladium atoms are brought into close contact so that to give rise to the observed ferromagnetism.
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