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  • Institute of Physics  (170)
  • International Union of Crystallography  (37)
  • American Institute of Physics (AIP)
  • 1
    Publication Date: 2024-03-13
    Description: The PERCIVAL detector is a CMOS imager designed for the soft X‐ray regime at photon sources. Although still in its final development phase, it has recently seen its first user experiments: ptychography at a free‐electron laser, holographic imaging at a storage ring and preliminary tests on X‐ray photon correlation spectroscopy. The detector performed remarkably well in terms of spatial resolution achievable in the sample plane, owing to its small pixel size, large active area and very large dynamic range; but also in terms of its frame rate, which is significantly faster than traditional CCDs. In particular, it is the combination of these features which makes PERCIVAL an attractive option for soft X‐ray science.
    Keywords: ddc:548 ; X‐ray detectors ; soft X‐rays ; ptychography ; holographic imaging ; XPCS ; detectors
    Language: English
    Type: doc-type:article
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 5423-5428 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An rf nitrogen (N) plasma source has been used to achieve p-type conductivity in molecular beam epitaxy CdTe layers grown with a Cd overpressure. Photoluminescence and secondary ion mass spectrometry measurements have confirmed the incorporation of the N species, and evidence for the resulting p-type conductivity has been obtained using capacitance-voltage and current-voltage techniques. Net hole concentrations as high as 2×1017 cm−3 have so far been achieved, which contrasts with the normally n-type nature of our undoped CdTe layers.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 5214-5217 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The use of Ar dilution in a N plasma source has been used to achieve control of both electrical and optical properties of p-type ZnTe:N grown by molecular-beam epitaxy. Photoluminescence data are presented that show the transition from "pure'' ZnTe emission to that indicative of heavily N-doped ZnTe. A new principal bound-exciton line associated with N impurities is observed at 2.3685 eV. An anomalous red shift in the corresponding donor-acceptor pair peak energy with increasing N concentration is observed at high N concentration and is attributed to the effects of N impurity banding. Trends in p-type conductivity confirmed the ability to control hole concentrations using Ar dilution.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 1895-1897 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The extent of interdiffusion in Cd1−xMnxTe/CdTe quantum-well structures grown by molecular-beam epitaxy was monitored by photoluminescence and photoluminescence excitation spectra. Thermal annealing of as-grown and ion-implanted structures in over pressures of cadmium (or tellurium) provide clear evidence that diffusion is controlled by cation vacancies and are consistent with a strong dependence of the interdiffusion coefficient on the vacancy concentration. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 4398-4400 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic graphite intercalation compounds (GIC's) allow a controlled separation of atomically abrupt magnetic layers by variation of the stage of the sample. Thus very small J'/J values (∼10−4) and quasi-two-dimensional behavior can be achieved where J' and J are, respectively, the interplanar and intraplanar exchange constants. The applicability of a 2D XY model is established by a comparison of the high-temperature susceptibility with the high-temperature series expansions for the various 2D and 3D models. Low-temperature studies provide values for magnetic interactions pertinent to the most interesting intermediate temperature range, where a 2D XY bound vortex phase may occur.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 1373-1379 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Studies of pulsed laser annealing (PLA) of CdTe/CdMnTe quantum well structures are made in order to examine depth dependent effects in laser irradiated semiconductors. Since diffusion coefficients are strongly dependent on the temperature, depth resolution is achieved because the diffusion of Mn from the barriers into the quantum wells is depth dependent. Multiple quantum well (MQW) structures of CdTe/CdMnTe were annealed with single pulses from an XeCl laser at 308 nm. At a threshold of 90 mJ cm−2 two new emission bands are observed that are attributed to the diffusion of Mn from barrier layers to QWs. The diffusion associated with these bands, measured as the integrated product of the diffusion constant and time, is found to be 300 and 30 Å2. Calculations of the temperature, reached within the surface following PLA, using an analytical solution of the heat diffusion equation coupled with known high temperature diffusion coefficients predict the diffusion to decrease by one order of magnitude within one period at the top of the MQW stack. It is suggested that at the threshold surface melting occurs and that these emission bands arise from the QWs immediately beneath the melt front. The diffusion of Mn ions into the QWs is confirmed by magneto-optical data. A further emission band occurs at this same threshold with a Mn concentration above that of the concentration in the barrier layers of the MQW stack. This emission is attributed tentatively to the segregation of the Mn ion within the molten region following recrystallization. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 4036-4038 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate how two two-dimensional electron gases can be independently contacted using only surface gates defined by electron-beam lithography: macroscopic bar gates to contact the lower layer, and mesoscopic split gates to contact the upper layer. When the technique is applied to a sample consisting of two 150 Å GaAs wells separated by 300 Å Al0.33Ga0.67As barrier, there is more than 30 MΩ isolation at 5 K for interlayer voltages up to ±30 mV; the interlayer isolation operates up to 30 K. The independent contacts are used for a preliminary investigation of two parallel one-dimensional quantum wires. © 2000 American Institute of Physics.
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 907-915 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Strained layer superlattices of wurtzite CdS/CdSe have been grown on (111)A GaAs substrates by metalorganic chemical vapor deposition and their optical properties studied by photoluminescence spectroscopy. It is shown that the superlattice layers contain giant strain-induced piezoelectric fields exceeding 2×108 V m−1. These fields are similar to those reported for (111) orientated III–V superlattices, but an order of magnitude greater. The recombination energies from a series of samples provide evidence for a type II conduction band offset of 0.23±0.10 eV (the electron wells being in the CdS), with the band structure heavily modified by the internal electric fields. In addition, the photoluminescence peak emission energy shows a strong dependence on the excitation power. This is interpreted as further evidence for the effect of internal fields. We conclude that this system shows new effects not previously observed in II–VI compound superlattices. The large band-gap tunability and the space-charge effects offer possibilities for all-optical switching devices in the 700–1300-nm region of the spectrum.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5746-5748 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report ac magnetic susceptibility (χ=χ'−iχ‘) measurements of stage-1 CoCl2-graphite intercalation compounds (GICs) carried out under hydrostatic pressures of 0–15 kbar. For stage-1 CoCl2 -GICs, it is found that the three-dimensional ordering temperature Tc2=TN=9.7 K, where the ferromagnetic planes of Co2+ spins become ordered into an antiferromagnetic arrangement along the c axis, shifts to a higher temperature with increasing pressure. Additionally, the transition field Ht, measured when a magnetic field is applied in the x-y plane, shifts to a higher field value with increasing pressure. From the increase of the transition field, we can estimate the pressure dependence of the antiferromagnetic interlayer coupling J'.
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 5621-5625 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The role of biexcitons has been studied in two optically pumped quantum well (QW) structures of Zn1−xCdxS/ZnS, one with 18% Cd concentration and the other with 3% in the wells. For the x=18% QW structure, high excitation photoluminescence and stimulated emission indicate that the laser gain mechanism involves biexcitons. For the x=3% QWs, even though biexcitons are clearly observed in the spontaneous emission, they are not responsible for laser gain in this structure. Instead exciton–exciton scattering may be the more likely mechanism responsible for laser gain close to threshold, while at higher densities an estimate of the carrier density indicates an electron–hole plasma as the likely source of optical gain. The different mechanisms in the two cases can, very likely, be attributed to one of differing degrees of localization both within the QW and at alloy fluctuations. © 1998 American Institute of Physics.
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