Physics / Fizik

Permanent URI for this collectionhttps://hdl.handle.net/11147/6

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End date: 1999Publisher: search.filters.publisher.American Physical Society

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  • Article
    Citation - WoS: 200
    Citation - Scopus: 212
    Predominantly Superconducting Origin of Large Energy Gaps in Underdoped Bi2sr2cacu2o8+? From Tunneling Spectroscopy
    (American Physical Society, 1999) Miyakawa, Nobuaki; Zasadzinski, John F.; Özyüzer, Lütfi; Guptasarma, Prasenjit; Hinks, David G.; Kendziora, Christopher A.; Gray, Kenneth E.
    New tunneling data are reported in Bi2Sr2CaCu2O8+δ which show quasiparticle excitation gaps, Δ, reaching values as high as 60 meV for underdoped crystals with Tc = 70 K. These energy gaps are nearly 3 times larger than those of overdoped crystals with similar Tc. Despite the large differences in gap magnitude, the tunneling spectra display qualitatively similar characteristics over the entire doping range. Detailed examination of the spectra, including the Josephson IcRn product measured in break junctions, indicates that these energy gaps are predominantly of superconducting origin.
  • Article
    Citation - WoS: 15
    Citation - Scopus: 14
    1/F-noise Study of Undoped Intrinsic Hydrogenated Amorphous Silicon Thin Films
    (American Physical Society, 1999) Güneş, Mehmet; Johanson, Robert E.; Kasap, Safa O.
    Conductance fluctuations in four samples of undoped intrinsic hydrogenated amorphous silicon (a-Si:H) were measured in the temperature range of 450 K to 500 K and for frequencies from 2 Hz to 3 kHz. The noise spectra divide into two regions that each fit a 1/fα power law but with different slope parameters α and different temperature dependences. At low frequencies, α is greater than unity and increases with temperature. At high frequencies, α is near 0.6 and temperature independent, but the noise magnitude decreases rapidly with temperature. We infer from the different dependences on temperature that the noise is generated by two independent mechanisms operating simultaneously in a-Si:H. We also observe that the 1/f noise exhibits a quadratic dependence on bias current and Gaussian statistics.