Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 3127-3129 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The structure of a Si(111)-(7×7) surface capped by a 200 A(ring) film of C60 was studied by grazing-incidence x-ray diffraction. The Si(111)-(7×7) reconstruction prepared in vacuum, including the loosely bonded "adatoms'' on the surface, is preserved under the C60 overlayer. This result illustrates that C60 can be used as an inert cap for surfaces and suggests potentially interesting applications in surface science research and electronic device engineering.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 400-405 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Piezoreflectance (PzR) and contactless electroreflectance (CER) measurements of an In0.86Ga0.14As0.3P0.7/InP quantum well heterostructure as a function of temperature in the range of 20–300 K have been carried out. A careful analysis of the PzR and CER spectra has led to the identification of various excitonic transitions, mnH(L), between the mth conduction band state and the nth heavy (light)-hole band state. The parameters that describe the temperature dependence of EmnH(L) are evaluated. A detailed study of the temperature variation of excitonic transition energies indicates that the main influence of temperature on quantized transitions is through the temperature dependence of the band gap of the constituent material in the well. The temperature dependence of the linewidth of 11H exciton is evaluated and compared with that of the bulk material. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Surface roughness was determined by x-ray diffraction for Ge films on Ge(001) grown by molecular beam epitaxy at room temperature. The truncation rod intensities and transverse-scan line profiles were measured as a function of perpendicular momentum transfer. Depending on the initial morphology of the surface, the same growth condition resulted in very different surface morphologies. Two types of initial surfaces were used. One was an atomically flat surface with very large terraces. The other, characterized by a roughness exponent α=1, had a high density of steps. Deposition on the flat surfaces resulted in a fairly smooth surface, but with a graded crystalline density below the surface. Deposition on the α=1 surfaces resulted in a more jagged surface characterized by an increase in the average height–height correlation function and a final roughness exponent of α=1/2. Additional and complementary information about the surface structure was obtained by scanning tunneling microscopy observations. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Surface morphological and compositional evolution during the initial stages of Si growth on Ge(001)2×1 by cyclic gas-source molecular beam epitaxy from Si2H6 has been investigated using in situ reflection high-energy electron diffraction (RHEED), Auger electron spectroscopy, electron-energy-loss spectroscopy, and scanning tunneling microscopy, combined with post-deposition high-resolution cross-sectional transmission electron microscopy. The layers were deposited using repetitive cycles consisting of saturation Si2H6 dosing at room temperature, followed by annealing for 1 min at 550 °C. Film growth was observed to proceed via a mixed Stranski–Krastanov mode. Single-step-height two-dimensional growth was obtained for nominal Si deposition thicknesses tSi up to (approximately-equal-to)1.5 monolayers (ML). However, the upper layer remained essentially pure Ge which segregated to the surface through site exchange with deposited Si as H was desorbed. At higher tSi, the Ge coverage decreased slowly, the surface roughened, and two-dimensional multilayer island growth was observed for tSi up to (approximately-equal-to)7.5 ML, where bulk reflections in RHEED patterns provided evidence for the evolution of three-dimensional island formula.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 947-949 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The surface effect on the spin-wave spectrum in two-sublattice ferrimagnets is investigated by means of the retarded Green's function equation of motion method. The two-sublattice Heisenberg model with nearest neighbor interactions is assumed in our discussion. We find that for a NaCl structure, the (001) free surface spin-wave spectrum splits up into acoustic and optical branches as usual. For the case of a CsCl structure, the (001) surface spin wave depends solely upon the nature of the magnetic ions in the surface layer. It has only the optical branch when the surface layer belongs to one sublattice, and has only the acoustic branch when the surface layer belongs to the other. Other properties are also discussed.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5905-5907 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have developed a new variational treatment to deal with the superconductivity properties of systems with strong electron-phonon interactions by introducing a "squeeze'' transformation for phonon operators. It is shown that as long as the renormalized intersite electron correlation is attractive, a new type of Cooper pairing occurs whether the renormalized on-site electron correlation is repulsive or atttractive. The transformed electron-phonon interaction gives rise to the squeezed polarons which are, in general, different from the ordinary polarons. We have found from this theory that: (1) the squeezed polaronic state corresponds to a stable minimum of the total energy; (2) the effective mass of the squeezed polaron is much smaller than that of ordinary polarons; (3) both the gap equation and the expression for the critical temperature Tc in squeezed polaronic states are different from those in ordinary polaronic states as well as from those in BCS theory; and (4) high Tc is obtained for simple cubic and body centered cubic lattice structures with the electron concentration n=1.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 7
    ISSN: 1365-2133
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background  Alopecia areata (AA) is hypothesized to be an organ-specific autoimmune disease with genetic predisposition and an environmental trigger. There are few clinical data in Asians.Objectives  To describe the genetic epidemiological features of AA patients in China and to determine the possible genetic model for AA.Methods  Data for 1032 patients with AA were obtained by questionnaire in the Institute of Dermatology of Anhui Medical University in China from 2001 to 2003. Complex segregation analysis and heritability analysis were performed using Falconer's method, EPI INFO 6·0 and SAGE-REGTL programs.Results  In total, 1032 AA patients (male/female ratio 1·1 : 1) were enrolled, representing 0·94% of the total number of cases seen in our outpatient clinic during that time. The mean ± SD age of onset was 28·98 ± 13·43 years. The difference between the mean age of onset in males and females was not significant. Most patients (82·6%) experienced their first episode of AA within the first four decades of life. A positive family history of AA was obtained in 87 patients (8·4%). The prevalence of AA in first-, second- and third-degree relatives of the proband with AA was 1·6%, 0·19% and 0·03%, respectively. These figures were higher than those in controls. A greater severity and longer duration of AA were seen in the early onset group than in the late-onset group. The early onset group also had more affected first- and second-degree relatives. The heritability of AA in first-, second- and third-degree relatives was 47·16%, 42·53% and 22·29%, respectively. Based on the REGTL results, the best model was a polygenic additive model for AA.Conclusions  The effect of genetic factors is strong in AA, but environmental factors such as infection and psychological stress may still play an important role. Our findings on the genetics of AA are consistent with a polygenic additive mode of inheritance.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 8
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Absolute partial cross sections for the production of CH4+, CH3+, CH2+ , CH+, C+, H2+, and H+ from electron-impact ionization of CH4 are reported for electron energies from threshold to 1000 eV. The product ions are mass analyzed using a time-of-flight mass spectrometer and detected with a position-sensitive detector whose output demonstrates that all product ions are completely collected. The overall uncertainty in the absolute cross section values is ±3.5% for singly charged parent ions and is slightly greater for fragment ions. Although previous measurements are generally found to agree well with the present results for CH4+ and CH3+, almost all previous work for the remaining fragment ions lies lower than the present results and in the case of H+ is lower by approximately a factor of 4. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 9
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Temperature-dependent contactless electroreflectance (CER) and photoluminescence (PL) measurements in the range of 30 K〈T〈300 K on two GaAlAs/InGaAs/GaAs pseudomorphic high electron mobility transistor structures with different well widths fabricated by molecular-beam epitaxy on (100) GaAs substrates are presented. For the CER measurement, the 11H transition is completely screened out by the two-dimensional electron gas and the prominent feature related to the Fermi energy edge singularity transition showed a Stokes shift to higher energy with respect to the 21H transition of the PL measurements at low temperature. From the Stokes shifts, the Fermi energy level of the system is evaluated, and hence, the density of the two-dimensional electron gas. The temperature-dependent PL measurements revealed two features, identified to be the 11H and 21H transitions. The relative intensities of the 11H and 21H transitions were analyzed taking into account the effect of the subband filling and the wave-function overlap factors. A good agreement is found between experimental data and theoretical calculation results. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 10
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using room-temperature photoreflectance (PR) and photoluminescence (PL) we have characterized four pseudomorphic AlGaAs/InGaAs/GaAs high electron mobility transistor structures with varied quantum well compositional profiles. Several features from the InGaAs modulation doped quantum well portion of the samples have been observed in addition to signals from the AlGaAs, GaAs, and GaAs/AlGaAs superlattice (SL) buffer layer. The PR spectra from the InGaAs quantum well channel can be accounted for by a line shape function which is the first derivative of a step-like two-dimensional density of states and a Fermi level filling factor. A detailed line shape fit makes it possible to evaluate the Fermi energy, and hence the concentration of two-dimensional electron gas in addition to the energies of the intersubband transitions. The lowest lying intersubband transition has been confirmed by a comparison of the PR and PL spectra. From the difference of intersubband transition energies, the surface segregation effects of indium atoms are demonstrated. In addition, other important parameters of the system such as built-in electric field, Al composition, as well as the properties of the GaAs/AlGaAs SL buffer layer are evaluated. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...