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  • 1
    Online Resource
    Online Resource
    Correlation between luminescence properties of AlxGa1−xAs∕GaAs single quantum wells and barrier composition fluctuation
    AIP Publishing ; 2007
    In:  Journal of Applied Physics Vol. 101, No. 11 ( 2007-06-01)
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 101, No. 11 ( 2007-06-01)
    Abstract: The luminescence mechanism at low temperatures in AlxGa1−xAs∕GaAs single quantum wells grown by molecular-beam epitaxy with different aluminum concentrations in the barrier has been studied in detail using the photoluminescence spectroscopy (PL) as function of temperature (8K⩽T⩽90K) combined with the excitation intensity. The asymmetry presented by the PL spectra at the low-energy side, the blueshift behavior of the PL peak energy, and the PL line broadening with increasing temperature are explained through the exciton localization in confinement potential fluctuations. The exciton localization effects on the PL spectra are progressively reinforced with the increase of the Al concentration in the barrier constituent material. The PL peak energy dependence on temperature has been fitted through the expression proposed by Pässler [Phys. Status Solidi B 200, 155 (1997)] adapted to systems with potential fluctuations, by subtracting the term σE2∕kBT, where σE is the standard deviation of the potential fluctuations. It was verified that σE increases systematically with the Al concentration in the barrier, according to the AlGaAs alloy compositional disorder theory.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.2745843
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2007
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    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 2
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    Online Resource
    Low temperature annealing of 4H–SiC Schottky diode edge terminations formed by 30 keV Ar+ implantation
    AIP Publishing ; 2000
    In:  Journal of Applied Physics Vol. 87, No. 8 ( 2000-04-15), p. 3973-3977
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 87, No. 8 ( 2000-04-15), p. 3973-3977
    Abstract: Edge termination of Schottky barrier diodes has been achieved using 30 keV Ar+ ions implanted at a dose of 1×1015 cm−2. The reverse-bias leakage current is reduced by 2 orders of magnitude following postimplant annealing at a temperature of 600 °C. The thermal evolution of the implantation induced defects was monitored using positron annihilation spectroscopy and deep-level transient spectroscopy. Two distinct defect regions are observed using the positron technique. The depth of the first is consistent with the range of the implanted Ar+ ions and consists of clustered vacancies. The second extends to ∼250 nm, well beyond the range of the incident ions, and is dominated by point defects, similar in structure to Si–C divacancies. An implant damage related deep level, well defined at Ec−Et=0.9 eV, is observed for both the as-implanted and the 600 °C annealed sample. The effect of annealing is a reduction in the concentration of active carrier trapping centers.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.372443
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2000
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 3
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    Online Resource
    Anomalous low-field magnetization in La2/3Ca1/3MnO3 near the critical point: Stable clusters?
    AIP Publishing ; 1998
    In:  Journal of Applied Physics Vol. 83, No. 11 ( 1998-06-01), p. 7154-7156
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 83, No. 11 ( 1998-06-01), p. 7154-7156
    Abstract: The magnetic behavior of bulk La2/3Ca1/3MnO3 (TC=267 K) at low fields in the paramagnetic phase was studied. Near TC(T−TC & lt;30 K) we find a sequence of steplike features in the effective Curie constant C(T)=M(T−TC)/H at well defined temperatures and intermediate plateaus, accompanied by temperature hysteresis. On approaching TC, the C values at each plateau follow a geometrical progression, with the effective spin S doubled at each step. The first plateau gives S=5.5, corresponding to a cluster of three Mn3+ ions sharing one extra hole. This suggests that close to TC short range magnetic order at low fields develops hierarchically through a series of most stable cluster states.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.367859
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1998
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
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  • 4
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    Online Resource
    Study of in situ adsorption kinetics of polyelectrolytes and liposomes using quartz crystal microbalance: Influence of experimental layout
    AIP Publishing ; 2015
    In:  Review of Scientific Instruments Vol. 86, No. 6 ( 2015-06-01)
    Details
    In: Review of Scientific Instruments, AIP Publishing, Vol. 86, No. 6 ( 2015-06-01)
    Abstract: Quartz Crystal Microbalance (QCM) is a widely used technique to characterize adsorption/desorption phenomena at the solid/liquid interface. However, the obtained adsorption/desorption kinetics curves are often not reproducible and present some noise and long term fluctuations. In this work, the accuracy of a commercial QCM to measure the adsorbed amount of polyelectrolytes and biological molecules was evaluated in terms of experimental QCM configurations with respect to quality, stability, and reproducibility of the measured data. Evaluation consisted in comparing the adsorption kinetics curves of the cationic polyelectrolyte poly(ethyleneimine) and the anionic 1,2-dipalmitoyl-sn-glycero-3-phospho-(1′-rac-glycerol) (sodium salt) liposomes, when setting the quartz crystal surface in stationary horizontal open, stationary horizontal closed, stationary vertical open, continuous vertical closed, and stationary vertical closed measuring configuration. For this last configuration, a new cell was designed and implemented. The analysis of the kinetics curves revealed that horizontal modes are more unstable when subjected to fostering noise due to the mechanical vibrations and lead to resonance frequency shift. This shift is caused by the measurement of non-adsorbed molecules which are deposited on the quartz crystal due to gravity force. The vertical modes proved to be more reproducible and reliable.
    Type of Medium: Online Resource
    ISSN: 0034-6748 , 1089-7623
    URL: Article
    DOI: 10.1063/1.4921715
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2015
    detail.hit.zdb_id: 209865-9
    detail.hit.zdb_id: 1472905-2
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  • 5
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    Online Resource
    Anisotropic electrical transport in epitaxial La2/3Ca1/3MnO3 thin films
    AIP Publishing ; 2000
    In:  Journal of Applied Physics Vol. 87, No. 9 ( 2000-05-01), p. 5570-5572
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 87, No. 9 ( 2000-05-01), p. 5570-5572
    Abstract: Epitaxial thin films of La0.62±0.05Ca0.33±0.02MnO3−δ were grown by laser ablation on SrTiO3. On (100) substrates the films grow with the larger c axis perpendicular to the plane. The films deposited on (110) SrTiO3 grow with both the c (long) axis and a (or b, short) axis in the plane of the film. The electrical resistivity (ρ) and the magnetoresistance (Δρ/ρ) show crystalline anisotropy. The resistivity ratio between the a and c axis is constant (0.8) from 10 K up to 120 K and decreases to 0.77 between 125 and 225 K, shows a small peak anomaly at Tc (257 K), and is almost constant in the paramagnetic phase. This temperature dependence is associated with anisotropic local lattice distortions. The magnetoresistance anisotropy (Δρ/ρ∥−Δρ/ρ⊥) with the applied field in the plane of the film, is small at low temperatures, peaks close to Tc, and is slightly larger for measurements along the a axis. The contributions of domain rotation and magnetocrystalline anisotropy to the anisotropic magnetoresistance associated with spin–orbit coupling are discussed.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.373407
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2000
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
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  • 6
    Online Resource
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    Influence of In on Si local vibrational modes in In x Ga1− x As (0≤ x ≤0.12)
    AIP Publishing ; 1994
    In:  Journal of Applied Physics Vol. 76, No. 12 ( 1994-12-15), p. 7797-7804
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 76, No. 12 ( 1994-12-15), p. 7797-7804
    Abstract: Local vibrational modes (LVM) of Si in substitutional sites have been observed by resonant Raman spectroscopy in highly doped (≥8×1018 cm−3) InxGa1−xAs layers, either relaxed or under strain, on [100] GaAs substrates. The peak frequency ωLVM of the Si on Ga site (SiGa) LVM in unstrained samples shifts to lower values with increasing In content. For x≤0.10 this shift is clearly higher than expected from a linear interpolation between the measured values in the binaries. The comparison between the SiGa peak frequency measured in both a full strained layer and a relaxed layer with similar composition provides a rough determination of the deformation potentials for the SiGaLVM in these layers: q/ω2LVM=−2.7±1 and p/ω2LVM=−2.5±1. As the In content becomes higher the width of the SiGa peak increases much more than that of the GaAs-like longitudinal optical-phonon peak, revealing the splitting due to the loss of local symmetry introduced by the In. New calibration factors for the Si-defect concentrations have been deduced, which allow estimation of the solubility limit for the Si incorporation in substitutional positions, which ranges from 2.3×1019 to 2.6×1019 cm−3 for the layers at the growth conditions used. The analysis of the integrated intensity of the LVM Raman peaks indicates that the degree of electrical compensation is clearly reduced for increasing In up to x≤0.05, due to both an increase of the solubility limit for Si in these layers and a saturation or slight reduction of the SiAs-related defect concentrations. This conclusion is also supported by Hall and plasmon measurements.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.358521
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1994
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
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  • 7
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    Ion beam synthesized Ru2Si3
    AIP Publishing ; 1999
    In:  Applied Physics Letters Vol. 75, No. 9 ( 1999-08-30), p. 1282-1283
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 75, No. 9 ( 1999-08-30), p. 1282-1283
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/1.124668
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1999
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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  • 8
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    Substrate, annealing, and Mn excess effects on La–Ca–MnO3 thin films grown by metalorganic chemical vapor deposition: A way to room-temperature Tc
    AIP Publishing ; 1999
    In:  Journal of Applied Physics Vol. 85, No. 8 ( 1999-04-15), p. 5411-5413
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 85, No. 8 ( 1999-04-15), p. 5411-5413
    Abstract: Oriented thin films of the La–Ca–MnO3 system with several Mn-excess compositions were prepared by aerosol-assisted metalorganic chemical vapor deposition. Depositions both on MgO (100) and LaAlO3 (100) substrates were performed at temperatures between 700 and 800 °C, with 30 min in situ oxygen annealing at the deposition temperature. The films deposited on LaAlO3 have much better structural quality with rocking curves of 0.3–0.7 full width at half maximum and higher Tc. For films with Mn excess, an ex situ annealing (800 °C for 1 h in flowing oxygen) increases Tc dramatically, from 180–190 K to values in the range 240–296 K, above the maximum Tc of the stoichiometric, optimally doped La0.67Ca0.33MnO3 composition. This behavior may be associated with the presence of La vacancies, which act as self-dopants, and whose role is enhanced after suitable annealing. The films present high magnetoresistance values in the vicinity of the critical temperatures: at 7 kOe, 32% for a film with Tc=279 K and 13% for a film with Tc=296 K. The magnetic properties of the films on MgO were degraded by annealing, probably due to Mg diffusion to the film.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.369994
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1999
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
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  • 9
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    Online Resource
    Temperature dependence of optical transitions in AlGaAs
    AIP Publishing ; 2001
    In:  Journal of Applied Physics Vol. 89, No. 11 ( 2001-06-01), p. 6159-6164
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 89, No. 11 ( 2001-06-01), p. 6159-6164
    Abstract: AlGaAs structures with different aluminum concentration (x=0.0, 0.17, 0.30, and 0.40) were characterized by photoluminescence and photoreflectance techniques. The temperature dependence of optical transitions in the temperature ranging from 2 to 300 K were investigated. Y. P. Varshni [Physica (Utrecht) 34, 194 (1967)] , L. Viña et al. [Phys. Rev. B 30, 1979 (1984)], and R. Pässler [Phys. Status Solidi B 200, 155 (1997)] models were used to fit the experimental points. The Pässler model gave the best adjustment to the experimental points. The tree models showed that the empirical parameters obtained through the adjustment of the experimental data in the three different models are aluminum composition dependent in the ternary alloy.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.1367875
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2001
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
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  • 10
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    Online Resource
    Thermophysical Properties of 1-Hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C6mim][(CF3SO2)2N]—New Data, Reference Data, and Reference Correlations
    AIP Publishing ; 2020
    In:  Journal of Physical and Chemical Reference Data Vol. 49, No. 4 ( 2020-12-01)
    Details
    In: Journal of Physical and Chemical Reference Data, AIP Publishing, Vol. 49, No. 4 ( 2020-12-01)
    Abstract: Published data on the thermophysical properties of ionic liquids are normally in disagreement if results from different laboratories, using different samples and different measurement protocols, are compared. This fact was recognized years ago at the level of the International Union of Pure and Applied Chemistry (IUPAC), which established IUPAC Project 2002-005-1-100 (Thermodynamics of ionic liquids, ionic liquid mixtures, and the development of standardized systems), with the main objective of recommending a reference ionic liquid, making reference-quality measurements on selected thermophysical properties of both the pure ionic liquid and its mixtures, establishing recommended values for the properties measured, and providing recommendations on measurement methods. The ionic liquid chosen was 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C6mim][(CF3SO2)2N] , because of its stability, low viscosity compared with that of most common ionic liquids, low water solubility, ease of preparation and purification, and commercial availability. Due to its hydrophobicity, it is capable of being obtained very pure, with water amounts as small as 20 ppm. This paper reports new results obtained with the sample of [C6mim][(CF3SO2)2N] synthesized in the IUPAC project, namely on density, speed of sound, surface tension, and refractive index, as well as thermal conductivity of a commercial sample at P = 0.1 MPa, as a function of temperature, and proposes reference data and reference data correlations for the density, speed of sound, heat capacity, surface tension, viscosity, electrical conductivity, thermal conductivity, refractive index, ion self-diffusion coefficient, and melting temperature of this ionic liquid at 0.1 MPa, as a function of temperature, using these and other data reported up to July 2020. Rheological measurements demonstrated that this ionic liquid is Newtonian.
    Type of Medium: Online Resource
    ISSN: 0047-2689 , 1529-7845
    URL: Article
    DOI: 10.1063/5.0023160
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2020
    detail.hit.zdb_id: 2006308-8
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