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  • 1
    Electronic Resource
    Electronic Resource
    Spin dynamics study in doped polyaniline by continuous wave and pulsed electron paramagnetic resonance (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 2958-2966 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Continuous-wave (cw) and pulsed electron paramagnetic resonance (pulsed EPR) techniques were used to investigate spin dynamics in moderately and slightly doped poly(o-methoxyaniline), a polyaniline derivative. EPR line shapes, measured by standard cw EPR, and relaxation rates, measured by electron spin–echo methods, were studied as a function of temperature, in the ranges 6–300 K (cw) and 6–100 K (pulsed). Experimental results were explained by a model which considered two types of spins: isolated polarons in an insulating matrix, and delocalized ones in conductive islands (clusters) formed by dopant aggregates. Experimental data agreed with the assumption that EPR spectra are generated by isolated polarons coupled to the clusters by dipole–dipole interactions. Furthermore, some experimental evidence suggests that spin dynamic within the clusters, which play an essential role in the interpretation of the EPR results, is determined by exchange interactions. Consequences of the proposed model are discussed. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480869
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  • 2
    Electronic Resource
    Electronic Resource
    Carbon delta-doped AlGaAs grown by metalorganic vapor phase epitaxy (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 1660-1662 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Good-optical-quality C delta-doped AlGaAs layers grown by metalorganic vapor phase epitaxy using CBr4 with the impurities confined over not more than 5 Å and with doping levels above 1×1012 cm−2 are obtained. Such layers are found to be adequate for use in the fabrication of nipi superlattices for amplitude modulation. Yet, little flexibility is found in the growth conditions, in particular for the V to III fluxes ratio, for obtaining such layers. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1382826
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  • 3
    Electronic Resource
    Electronic Resource
    Impedance spectroscopy evidence of the phase separation in La0.3Pr0.4Ca0.3MnO3 manganite (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 6636-6638 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured electrical resistance R(T), magnetization M(T), and for the first time impedance spectroscopy Z(T,ω) of polycrystalline samples of La0.3Pr0.4Ca0.3MnO3 compounds. The combined results suggest the coexistence of two metallic ferromagnetic phases below the Curie temperature of the system. The R(T) data exhibit two important features: the occurrence of a metal–insulator (MI) transition at temperatures close to TMI(approximate)170 K and a large thermal hysteresis below TMI. The first feature was found to be associated with the development of ferromagnetism and takes place when the magnetization of the samples becomes about 15% of its saturated value at low temperatures. The second feature suggests two contributions to R(T) below the Curie temperature TC. The Z(T,ω) data taken from 77 to 300 K and frequency varying from 5 to 107 Hz are much more valuable. These results reveal two well defined bulk contributions to the transport properties of these manganites below ∼170 K: one occurring at high frequencies ∼4×106 Hz and a second one at low frequencies, typically on the order of 1.5×105 Hz. An analysis of the Z(T,ω) data suggests that these contributions are related to the spin lattice relaxation rate of the two distinct phases. Such a result suggests a phase separation below TC in the compound in complete agreement with recent muon spin relaxation and neutron spin echo measurements performed on manganites. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1357139
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  • 4
    Electronic Resource
    Electronic Resource
    New and simple mass calibration procedure for time-of-flight studies of electron stimulated desorption of ions from solid samples (2001)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 72 (2001), S. 2827-2828 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A technique that provides a simple mass scale calibration for linear time-of-flight (TOF) measurements is presented. This procedure has been used in the calibration of the mass scale in experiments of electron stimulated desorption of ions from solid surfaces. It is based on the admission of one or more calibration rare gases inside the ultrahigh vacuum chamber while a TOF spectrum of desorbing ions from the surface is simultaneously recorded. Peaks related to desorbing ions as well as to the atomic gases can consequently be observed in the same mass spectrum, thus allowing an exact mass scale calibration. The present calibration procedure is especially suitable in the low mass range (〈200 amu) and can be easily adapted for photon stimulated desorption experiments. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1367367
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  • 5
    Electronic Resource
    Electronic Resource
    Mechanical strain and damage in Si implanted with O and N ions at elevated temperatures: Evidence of ion beam induced annealing (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 42-46 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The accumulation of damage and the development of mechanical strain in crystalline Si (c-Si) by O and N ion implantation to doses up to 4×1017 cm−2 at elevated temperatures have been studied using Rutherford backscattering spectrometry and high resolution x-ray diffraction. The implantation of O or N ions at high temperatures produces two distinct layers in the implanted c-Si: (i) a practically damage-free layer extending from the surface up to (similar, equals) half of the depth of the mean projected range (Rp) and presenting negative strain (of contraction); and (ii) a heavily damaged layer located around and ahead of the Rp with no significant strain. Both the damage distribution and the magnitude of the strain were found to be dependent on the ion species implanted. We proposed that besides the spatial separation of Frenkel pair defects due to the mechanics of the collision processes and the intensive dynamic annealing, an ion beam induced annealing process also participate in the formation of the near-surface damage-free layer during high temperature implantation of c-Si. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1330254
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  • 6
    Electronic Resource
    Electronic Resource
    Damage accumulation in Si crystal during ion implantation at elevated temperatures: Evidence of chemical effects (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 8385-8388 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Damage in Si induced by irradiation with various light/medium mass ions at elevated temperatures and high doses (≥3×1016 cm−2) was studied using Rutherford backscattering spectroscopy, cross-section transmission electron microscopy, and high resolution x-ray diffraction. The results obtained have shown that there is a marked variation in the damage accumulation for different ion species. For O+ and N+ ions a distinct layer with a low level of damage presenting negative strain is formed at the surface. It has been found that the magnitude of the strain does not correlate with the energy deposited in the collision cascades. In the cases of Ne+ and Mg+ implantation, a low damage accumulation occurs near the surface but no negative strain is formed. In contrast to the N+ and O+ cases, with the increase of the Ne+ or Mg+ dose (〉1×1017 cm−2) the damage profile stretches almost to the crystal surface. It is proposed that in addition to the mechanism of spatial separation of Frenkel pairs taking place in the collision cascades, the ability of the implanted ions to form precipitates and complexes with Si atoms noticeably influences the damage formation during implantation at elevated temperatures. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373551
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  • 7
    Electronic Resource
    Electronic Resource
    Low field Overhauser images of the formation process of a hydrogel (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 160-162 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The gelation of sodium alginate by calcium ions is studied by proton-electron double resonance imaging in a magnetic field of only 16 mT using a newly developed free radical. The high sensitivity of the Overhauser enhancement to small variations in water mobility permits the detection of minute changes in gel composition. Spatial inhomogeneity and temporal evolution of this, and possibly other processes involving diffusion and chemical reaction, could be accurately monitored by this technique. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1429755
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  • 8
    Electronic Resource
    Electronic Resource
    Electrical activation of carbon in GaAs: Implantation temperature effects (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 1700-1702 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Carbon was implanted into GaAs at the energy of 1 MeV with doses between 1×1013 and 2×1015 cm−2 at temperatures of 80 K, nominal room temperature (RT), and 300 °C. A markedly higher electrical activation was obtained in the samples implanted at 80 K compared to those implanted at RT or 300 °C, attaining a maximum hole concentration of 2×1019 cm−3. The redistribution of the C profile during rapid thermal annealing at temperatures from 700 to 950 °C for 10 s was found negligible, independently of the implantation temperature. Similar improvements in the electrical properties were also verified in samples implanted at 80 K with a lower energy of 60 keV. We consider that despite the light mass of C ions, the reduced dynamic annealing at 80 K allows the accumulation of an abundance of As vacancies, which assist the C activation as a p-type dopant. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1356729
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  • 9
    Electronic Resource
    Electronic Resource
    Strong interface-induced changes on the numerical calculated Raman scattering in Si/3C–SiC superlattices (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 4316-4318 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Raman spectra of (3C–SiC)8−δ/(3C–SiC0.5Si0.5)δ/(Si)8−δ/(3C–SiC0.5Si0.5)δ superlattices with interfacial transition regions of thickness δ varying from one to three monolayers are calculated. It is shown that severe frequency shifts (up to −86 cm−1) and the flattening of the folded optical phonons dispersion curves are due to the interfacial regions, strongly affecting the Raman spectrum in consequence. With increasing interface thickness, the Raman peaks are enhanced in the middle frequency range. These effects are mainly attributed to localization of atomic displacements at the Si/3C–SiC or the 3C–SiC/Si interfacial transition regions. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1328763
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