Bibliothek

feed icon rss

Ihre E-Mail wurde erfolgreich gesendet. Bitte prüfen Sie Ihren Maileingang.

Leider ist ein Fehler beim E-Mail-Versand aufgetreten. Bitte versuchen Sie es erneut.

Vorgang fortführen?

Exportieren
  • 11
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 671-675 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have investigated magneto-transport and cyclotron resonance (CR) of two-dimensional electron gas in silicon δ-doped p-InSb under a magnetic field of up to 12 T at 4.2 K. Because there are multiple subbands occupied, Shubnikov–de Haas oscillations show a beating behavior. The CR spectra also display several peaks originating from different subbands. Effective masses of electrons associated with the lowest three subbands can therefore be directly determined, and they are in excellent agreement with a self-consistent calculation, which takes into account the electrostatic Poisson equation, the Schrödinger equation, and realistic sample parameters. Furthermore, we observed an absorption peak, whose resonance position has anomalous angle dependence. It is attributed to impurity CR where donors are in the vicinity of the δ-doped sheet.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 12
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 6731-6732 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A recent study of the effect of photoquenching of EL2 on the compensation of carbon acceptors in GaAs and the resulting effect on the carbon local vibrational mode, LVM, concluded that there was no broadening of the LVM associated with bound holes on neutral carbon acceptors. The failure to observe broadening of the LVM in this study was a result of the failure to neutralize a significant fraction of the carbon atoms by photoquenching EL2. We show that, in the experiment reported, at most only about 3%–4% of the carbon acceptors were neutralized. Such very small modifications of the ionized carbon concentration are unobservable in the LVM spectra unless the spectral stability and signal-to-noise ratio are exceptional.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 13
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1805-1809 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Silicon carbide grown by the chemical vapor deposition process on silicon often contains high concentrations of nitrogen donors with a binding energy of 54 meV as determined from photoluminescence studies. In contrast, the conductivity in the same samples is dominated by a heavily compensated shallow donor with a binding energy below 20 meV. The conventional view is that these two donors are the same. The 54 meV donors usually are assumed to be isolated substitutional nitrogen in regions of low concentration while the 〈20 meV donors are believed to be nitrogen in regions of high concentration. The most convincing evidence for this identification is the continuum of binding energies from 50 to 15 meV for SiC as a function of donor concentration compiled from published results. Evidence for reassessing the conventional view is given in this article and several experiments supporting the conventional view are reconsidered. As a result of this reconsideration, we propose that the donors below 20 meV which dominate the conductivity are not neutral, substitutional nitrogen in high concentration but some other center. D− centers and donor complexes are possible origins of this donor. The D− center appears to have many of the characteristics required for satisfactory modeling of this material.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 14
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 8192-8194 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Infrared photoluminescence has been used to study the band-gap energy of InAs1−xSbx digital superlattices and band alignment of InAs1−xSbx/AlSb quantum wells at 5 K. It is found that the InAs1−xSbx digital alloys have a smaller effective band gap than InAs1−xSbx random alloys. In addition, the valence band offset between type-II InAs/AlSb is determined to be 130 meV. This number reduces as the Sb mole fraction in InAs1−xSbx is increased, and the alignment between InAs1−xSbx/AlSb becomes type I when x〉0.15. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 15
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 6632-6635 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Transmission spectra of GaSb have been obtained over a temperature range from 10 to 470 °C. Using this information, transmission thermometry is applied to obtain accurate measurements of sample temperature during molecular beam epitaxy growth on GaSb substrates. A GaSb surface reconstruction transition is determined as a function of Sb flux and substrate temperature, establishing a laboratory-independent temperature standard. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 16
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 54 (1990), S. 0 
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: Activation of phosphoinositide metabolism is an early event in signal transduction for a number of neurotransmitters and hormones. In primary cultures of rat neurocortical cells, various excitatory amino acids stimulate inositol phosphate production with a rank order of potency of quisqualate 〉 ibotenate 〉 glutamate 〉 kainate, N-methyl-d-aspartate 〉 α-amino-3-hydroxyl-5-methyl-4-isoxazole propionate. This response to excitatory amino acids was insensitive to a variety of excitatory amino acid antagonists including 6-cyano-7-nitroquinoxaline-2,3-dione, 3–3(2-carboxypiperazine-4-yl)propyl-l-phosphonate, and 2-amino-4-phosphonobutyrate. The individual responses of quisqualate-, ibotenate-, and kainate-stimulated inositol phosphate production were not additive. These results suggest that phosphoinositide metabolism activated by excitatory amino acids is mediated by a unique quisqualate-preferring receptor that is not antagonized by known N-methyl-d-aspartate and non-N-methyl-d-aspartate antagonists, and is relatively insensitive to α-amino-3-hydroxyl-5-methyl-4-isoxazole propionate.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 17
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    BJOG 95 (1988), S. 0 
    ISSN: 1471-0528
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Summary. Growth of the fetal biparietal diameter (BPD) throughout the second and third trimesters was measured in a prospective longitudinal study. Linear-cubic equations were fitted to the data of individual fetuses and from these equations mean growth curves were produced for males and females. The head growth trajectories of males and females were significantly different. The study illustrates why the practice of dating pregnancies by ultrasonic fetal BPD measurement at about 16 weeks gestation can lead to error.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 18
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Science Ltd
    Child 26 (2000), S. 0 
    ISSN: 1365-2214
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin , Psychologie
    Notizen: The time spent by 158 infants in contact with their carers at 6, 13, 26 and 52 weeks was reviewed prospectively. Periods of contact in the categories of (1) physical care, (2) holding the crying or sleeping infant, and (3) playing and interacting with the infant were recorded using 24-h log diaries completed by the mother. The mean total carer contact time over a 24-h day did not change significantly in the first year, varying between 6.5 and 7.3 h. Between 6 and 52 weeks, time spent by the mother in physical care declined significantly from 207 to 143 min and in holding the crying or sleeping infant from 61 to 17 min (P〈 0.05 and 0.0001 respectively). There were no significant changes in the amount of time spent in playing and interacting with the infant over the first year by the mother and father, the time being on average 52.7 and 25.0 min respectively. Play and interaction with a non-parental carer increased significantly from 14 to 69 min (P〈 0.0001). Relationships between infant size and holding became weaker as the infant became older. Infant gender, socioeconomic status and duration of breast-feeding did not influence infant contact time.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 19
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 7255-7258 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The real dielectric constant for chemical vapor deposition 3C-SiC grown on silicon (Si) has been determined at 300 K and at 5 K from an analytic fit to interference fringes in transmission over the spectral range from the near infrared to the submillimeter region. This technique is capable of high accuracy being limited typically by the sample thickness and accuracy with which the thickness is measured. The resulting real dielectric constant is lower than the values usually attributed to this material. We find: at 300 K ε 0=9.52 and ε ∞=6.38; at 5 K ε0=9.28 and ε ∞=6.22. In all cases the estimated error is ±0.8%. The observed ratio ε0 /ε∞ agrees with the Lyddane–Sachs–Teller relation to 0.1% at 300 K and 0.2% at 5 K. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 20
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 6939-6942 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The real dielectric constant of gallium arsenide has been determined at 300 and at 5 K from fits to observed interference in transmission of thin samples with parallel surfaces. Measurement was carried out over all or part of the range 30–4000 cm−1. An accuracy of ±0.5% is estimated based on the quality of the analytic fits and the sample thickness measurement technique. We find at 300 K, ε0=12.90 and ε∞=10.86. At 5 K, ε0=12.46 and ε∞=10.58. An analytic expression for the dielectric function is given which allows accurate values of the real dielectric constant to be determined throughout most of the 0–4000 cm−1 spectral range. The observed ratio ε0/ε∞ agrees with the Lyddane–Sachs–Teller relation calculated with Raman values of transverse and longitudinal optical phonon frequencies to better than 0.1% at 300 and at 5 K. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
Schließen ⊗
Diese Webseite nutzt Cookies und das Analyse-Tool Matomo. Weitere Informationen finden Sie hier...