Results 1 - 10 of 639
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[en] We report on the infrared spectroscopic studies of the normal-state electronic response of rare-earth ternary platinum germanide superconductor La_2Pt_3Ge_5. We analyzed the temperature-dependent optical conductivity spectra using the Drude-Lorentz oscillator model. We found that the two Drude responses with distinct scattering rates are required to explain the charge dynamics at 10 K while a single Drude mode could reproduce the far-infrared conductivity at higher temperatures. Our results indicated the two-band character of the electronic structure and highlighted the disparate temperature evolution of the electrodynamics of the two electronic states
[en] Data on the synthesis, reactions and structures of stable aromatic tellurols and sterically hindered tellurols containing E-TeH bonds (E = C, Si or Ge) are systematised and generalised. Methods for the preparation of various metal derivatives of tellurols as well as applications of these derivatives in the low-temperature synthesis of metal tellurides are considered. The bibliography includes 90 references.
[en] To research the recombination processes spectral and time dependences of lateral photoconductivity nanoheterostructures Si/Ge with SiGe nanoislands, obtained by molecular beam epitaxy were studied. Photoconductivity at T<190 K, in the spectral region where Si is transparent, is conditioned due to transitions involving localized states nanoislands SiGe. It is shown that when the temperature was decreased the most significant is the decrease in the photoconductivity of the fundamental absorption of nanoislands
[en] This review covers recent developments in our group regarding the synthesis, characterization and applications of single-crystalline one-dimensional nanostructures based on a wide range of material systems including noble metals, metal silicides and metal germanides. For the single-crystalline one-dimensional nanostructures growth, we have employed chemical vapor transport approach without using any catalysts, capping reagents, and templates because of its simplicity and wide applicability. Au, Pd, and Pt nanowires are epitaxially grown on various substrates, in which the nanowires grow from seed crystals by the correlations of the geometry and orientation of seed crystals with those of as-grown nanowires. We also present the synthesis of numerous metal silicide and germanide 1D nanostructures. By simply varying reaction conditions, furthermore, nanowires of metastable phase, such as Fe5Si3 and Co3Si, and composition tuned cobalt silicides (CoSi, Co2Si, Co3Si) and iron germanides (Fe1.3Ge and Fe3Ge) nanowires are synthesized. Such developments can be utilized as advanced platforms or building blocks for a wide range of applications such as plasmonics, sensings, nano-electronics, and spintronics
[en] Recent studies of FeSi(1-x)Gex, which found a transition from an insulating to a magnetic metallic state near x=0.25, have revived the discussion about the role of strong correlation in these systems. Here are spin-polarized band calculations made for 64-atom supercells of FeSi(1-x)Gex for different x and different volumes for large x. The results show that the small band gap in FeSi is closed for x>=0.3, because of both substitutional disorder and increased volume. Ferromagnetism appears near this composition and becomes enforced for increasing x. The x-dependence of the electronic specific heat can be understood from the exchange splitting of the density-of-states near the gap. Strong volume dependencies for the properties of FeGe suggest experiments using pressure instead of x for investigations of the gap
[en] YbM6Ge6 (M - Fe, Co, Mn) composition germanides structure is determined. By means of powder technique it is proved that YbFe6Ge6 and YbCo6Ge6 compounds are crystallized in YCo6Ge6 structure type, while YbMn6Ge6 compound - in HfFe6Ge6 structure type
[en] The change of electrical performances of 1 MeV electron irradiated silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) and Si bipolar junction transistor (BJT) was studied. After electron irradiation, the collector current IC decreased while the base current IB did not change, and the current gain β decreased for SiGe HBT. For conventional Si BJT, both IC and IB increased and β decreased much more obviously than SiGe HBT at the same fluence. It was shown that SiGe HBT had a better anti-radiation performance than Si BJT. The mechanism of electrical performance changes induced by irradiation was preliminarily discussed. (authors)
[en] We report on the detection of the superconducting transition Tsc in the superconducting ferromagnet UGe2 by AC calorimetry under pressure. Our results confirm the small value of the specific heat jump. We suggest that this observation is intrinsic in origin and does not arises from a distribution of Tsc due to pressure gradient or sample defects.
[en] The 2d carriers in modulation doped quantum wells of Si defined by Si0.75Ge0.25 barriers exhibit an extremely sharp (ΔH < 30 mG) electron spin resonance (ESR) that allows for a detailed investigation of the relevant spin decoherence processes. We found that for high mobility samples the Bychkov-Rashba effect dominates both spin-decoherence and spin lifetime and also the g-factor anisotropy. In this contribution we report on quantitative investigations of the Bychkov-Rashba coefficient in SiGe channels. For samples with 4 % and 10 % Ge in the well (but constant Ge content in the barrier, 25 %) we find an increase of the Bychkov-Rashba coefficient a by 40 % and 120 %, respectively. These values are derived independently from the anisotropies of the g-factor and the linewidth. Both methods yield at the same value for the Rashba coefficient within the experimental accuracy. The resulting shift of the ESR field exceeds the (broadened) linewidth already for the 4 % sample by more than a factor of 3, which shows that Ge admixture may be a suitable tool to allow g-factor tuning. (author)
[en] Full text: Rare-earth intermetallic compounds containing ytterbium exhibit a wide range of interesting and unusual physical and magnetic properties. This occurs mainly as a result of their mixed valence states (II/III) or changes from one valence state to the other. Here we present a set of results for the YbMn2SixGe2-x series (8 samples from x = 0 to 2), focusing on the magnetic structure and valence state of these compounds as investigated by neutron powder diffraction (2-530 K). We have found that the valence state of the Yb ion changes from the trivalent state of YbMn2Si2 to a divalent-like behaviour for YbMn2Ge2 with increasing Ge concentration x, with significant changes in the magnetic structure taking place around 1.5< x<1.9. An overview of the structural and magnetic changes that occur around this critical concentration region will be presented. Emphasis will be placed on current research that focuses on the compound YbMn2Si0.3Ge1.7 in an attempt to characterise the transition