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  • 1
    Digitale Medien
    Digitale Medien
    Oxidation state and superconducting properties of Y1−xPrxSr2Cu2.85Re0.15O7+δ (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 6884-6887 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Superconductivity exists in orthorhombic Y1−xPrxSr2Cu2.85Re0.15O7+δ up to a critical concentration (xcr) of 0.65. A progressive decrease in Tc occurs as x increases from 0 to 0.65. A further increase in x leads to a tetragonal transformation and as a consequence the Tc vanishes; however, the orthorhombicity of these Sr-based compounds is much lower than that observed for the Ba analog, Y1−xPrxBa2Cu3O7−δ and, hence, the Tc. On the one hand, crystal chemistry correlations indicate that the Pr ion is in trivalent state while on the other hand, the stabilizing cation, viz., Re, is in hexavalent state which accounts for the excess oxygen (〉7.0) in the system. The high xcr value of the Sr series compared to the Ba series (xcr=0.55) is attributed to the much reduced orbital overlap of the trivalent Pr(4f ) state with the Cu(3dx2−y2)–O(2p) conduction band, via hole localization and/or pair breaking, and is not due to the much discussed hole filling by tetravalent Pr. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.363758
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  • 2
    Digitale Medien
    Digitale Medien
    Photoreflectance and photoluminescence spectroscopy of low-temperature GaAs grown by molecular-beam epitaxy (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 427-432 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Photoreflectance (PR) and photoluminescence (PL) measurements have been carried out on low-temperature GaAs (LT GaAs) and LT-GaAs/AlGaAs modulation-doped photodetector (MODPD) structures grown by molecular-beam epitaxy. Samples with LT GaAs grown at 350 °C show several PL lines associated with (i) transitions involving two-dimensional electron gas in LT GaAs near the interface, (ii) band-edge transitions in the bulk LT GaAs, and (iii) transitions involving deep level defect complexes in LT GaAs. In addition a PL emission band at 1.65 eV observed in all the MODPD structures is attributed to a crossover transition at the LT-GaAs/AlGaAs interface. PR spectra of these modulation-doped structures show Franz–Keldysh oscillations which are attributed to high electric fields ((approximately-greater-than)105 V/cm) at the LT-GaAs/AlGaAs interface. PR measurements on bare LT-GaAs layers suggest that the E0 transition in LT GaAs is about 20 meV above that of the normal GaAs E0 gap. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.360848
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  • 3
    Digitale Medien
    Digitale Medien
    Photoluminescence from modulation doped AlGaAs/ low-temperature molecular beam epitaxy-grown GaAs heterostructures (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 1210-1213 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Photoluminescence (PL) results from a novel modulation doped AlGaAs/ low-temperature molecular beam epitaxially-grown-GaAs (LT-GaAs MODFET) heterostructure are reported. A new PL line at 1.65 eV is consistently observed in all the LT-GaAs MODFET structures investigated. A spatially indirect transition from a two-dimensional electron gas at the heterojunction interface to the holes in AlGaAs is believed to be responsible for the observed 1.65 eV PL line. LT-GaAs MODFET structures in which LT-GaAs region is grown at 350 °C show additional lines lying in the band edge region as well as deep inside the band gap region of LT-GaAs. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.360359
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  • 4
    Digitale Medien
    Digitale Medien
    A low cost remotely operable cutting machine for segmenting metal clad ceramic fuel pellets (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 1618-1619 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Cutting of irradiated zircaloy metal clad ceramic fuel pellets requires a special cutting saw that can be remotely operated. The remote operation is essential because of the pyrophoric nature of zircaloy metal and high radiation field associated with the irradiated fuel elements. Conventional saws cannot meet the operational requirements because these are not readily amenable for remote operation and maintenance. Hence we have developed a new laboratory scale cutting saw for cutting radioactive samples remotely. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1147936
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  • 5
    Digitale Medien
    Digitale Medien
    Deep-level admittance spectroscopy of DX centers in AlGaAs:Sn (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 3955-3958 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Deep-level admittance spectroscopy (DLAS) of DX centers in AlxGa1−xAs:Sn (0.2〈x〈0.6) reveals the presence of three levels SN1, SN2, and SN3 related to the Sn donor. While SN1 and SN3 are observed in all the samples, SN2 is prominently seen only in the indirect band-gap samples. The conventional capacitance deep-level transient spectroscopy (DLTS) is found to be unsuitable for the study of the DX center in AlxGa1−xAs:Sn with x〉0.35 because of the strong freeze-out of free carriers in these samples. Even in the case of low AlAs mole fraction samples (x〈0.35), the DLTS technique fails to reveal all the levels observed by DLAS and provides information only on the SN3 level.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.344029
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  • 6
    Digitale Medien
    Digitale Medien
    Frequency dependence of response of the DX center in AlGaAs and its influence on the determination of the band discontinuity of GaAs/AlGaAs heterojunctions (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 1211-1214 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: An analysis to simulate the apparent carrier profiles of n-N heterojunctions obtained from capacitance-voltage measurements is presented. The analysis takes into account the partial ionization and the frequency dependence of the response of deep donors, if any, present in the N material. In the case of GaAs/AlGaAs heterojunctions, the latter effect has not been included in the previous analyses but appears to be important since the reciprocal time constant of the Si-related DX centers in AlGaAs at room temperature seems to be comparable to the frequency of the test signal (1 MHz) normally used for capacitance measurements.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.341887
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  • 7
    Digitale Medien
    Digitale Medien
    Influence of test signal frequency on the determination of band discontinuity of GaAs/AlGaAs heterojunctions from capacitance-voltage measurements (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 1552-1554 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have simulated the effects of deep donors in AlGaAs (DX centers) in the determination of band discontinuity (ΔEc) of GaAs/AlGaAs heterojunctions using the capacitance-voltage measurements. In addition to the partial ionization of the deep donors, the ability of the traps (deep donors) to respond to the test signal used for capacitance measurement has also been included in the analysis. We find that the deep-level effects lead to an underestimation or overestimation of ΔEc, depending upon whether the frequency of the test signal is low or high, respectively, as compared to the emission rate of the traps.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.341832
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  • 8
    Digitale Medien
    Digitale Medien
    Stabilization of a superconducting TbSr2Cu2.85Re0.15O7+δ compound and the valence state of terbium (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 2711-2713 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A single-phase Sr-based Tb-123 phase has been synthesized by chemical stabilization. TbSr2Cu2.85Re0.15O7+δ exhibits superconductivity at Tc,zero=22 K. X-ray diffraction results suggest a relatively small orthorhombicity and neutron diffraction studies indicate an excess oxygen content (≥7.2) in the sample. Tb is present as a trivalent ion in the superconducting phase as derived from x-ray photoelectron spectroscopy. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.114301
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  • 9
    Digitale Medien
    Digitale Medien
    Zero field tensor for Ni(II) in Zn (ethylenediamine)3 (NO3)2: EPR study (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 43-45 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Single crystal EPR of Ni(en)2+3 (en=ethylenediamine) doped in Zn(en)3(NO3)2 is reported. Our results beased on exact diagonalization procedure indicate that the Ni(en)2+3 units undergo distortion along the threefold axis which coincides with the crystallographic c axis. The zero field tensor is found to be axially symmetric with D being 0.831±0.006 cm−1. The utility of S=1 ions in obtaining information regarding molecular distortions is also evidenced.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.454621
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  • 10
    Digitale Medien
    Digitale Medien
    On the charge compensation effects in Mn(II) doped (NH4)2SbF5: EPR study (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 83 (1985), S. 1485-1489 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Electron paramagnetic resonance of Mn(II) ion doped in bis (ammonium) pentafluorostibnate is reported. Local charge compensation is proposed as the reason for the doubling of the expected single site. A ±20° rotation of the MnF3−5 moeity about the crystallographic a axis has been attributed to charge compensation processes. The D tensor is found to have the values Dzz=0.0358 cm−1, Dyy=−0.028 62 cm−1, Dxx=−0.007 26 cm−1; the Mn hyperfine coupling is found to be −0.0095 cm−1. The apical flourine does not give resolved hyperfine coupling, while the four basal flourine atoms give hyperfine couplings in the range amax=0.0018 cm−1, amin=0.0015 cm−1.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.449383
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