Library

feed icon rss

Your email was sent successfully. Check your inbox.

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

Proceed reservation?

Export
  • 1
    ISSN: 1432-0630
    Keywords: 36.20.Kd ; 85.60.Jb ; 72.20.−i
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The observation of electroluminescence from crystalline fullerenes is described and discussed for the first time. Using gold and aluminium electrodes as contacts, a broad band emission spectrum, extending from 400 nm to 1100 nm is observed. The spectrum has a primary maximum at 920 nm and a weaker feature centered on 420 nm. The spectral characteristics are independent of the applied field and the longer wavelength region is identical to that measured in the high excitation density photoluminescence spectrum. In addition, the electroluminescent output intensity increases with the cube of the injection current, strengthening the association to the nonlinear phenomena observed in the highly excited state of fullerenes.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 56 (1993), S. 235-239 
    ISSN: 1432-0630
    Keywords: 33.50.Dq ; 42.65.Vh ; 42.70.Jk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Time-resolved photoluminescence studies in powders and single crystals of C60 are reported. The observed emission spectra, resulting from excitation above the HOMO-LUMO transition energy, are consistent with those reported for steady state conditions which may be associated with an intramolecular process and the observed luminescence decay times are of the order of 1 ns. No long lived decay from the triplet is observed at low intensities. A dramatic increase in the lifetime as well as a redshift and broadening of the spectrum is observed at high excitation densities. The luminescence intensity is seen to increase with the cube of the input intensity. The phenomenon is interpreted as an abrupt onset of emission from the highly populated excited state resulting from an interaction of the intramolecular states, a process which is dependent on a critical excited state density. Furthermore, the phenomenon may be photoexcited at photon energies which lie below the HOMO-LUMO transition energy, under which conditions an intensity dependence of the output luminescence on input to the sixth power is observed. Under “off-resonant” conditions the process is interpreted as two-photon assisted nonlinear emission.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1432-0630
    Keywords: 33.90.+h ; 36.20.Kd ; 71.30.+h
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Under high intensity illumination, the optical and electronic properties of fullerenes are seen to undergo dramatic, nonlinear changes. The photoluminescence emission is seen to increase with approximately the third power of the input intensity above an apparent threshold intensity. Associated with this nonlinear increase is the emergence of a long lifetime emission component and a redshifting of the emission spectrum. Investigations of the photo-transport properties associate the observed behaviour with a phase transition in the highly excited state. Above an intensity which coincides with the onset of the nonlinear emission, the photoconductive response increases with approximately the cube of the input power. In the highly excited state, the photoconductive response becomes relatively temperature independent compared to the thermally activated behaviour observed at low intensities. The characteristics of the temperature dependence are associated with a high electron mobility phase in the highly excited state and therefore an optically driven insulator to metal transition is proposed as a description of the observed phenomena.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Single-walled carbon nanotubes (SWNTs) offer the prospect of both new fundamental science and useful (nano)technological applications. High yields (70–90%) of SWNTs close-packed in bundles can be produced by laser ablation of carbon targets. The electric-arc technique used to generate ...
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 1432-0630
    Keywords: 72.20.−i
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract We report about dc, ac (100Hz≦v≦100kHz) and contactless microwave (10 GHz) conductivity studies on C60 crystalline bulk material from room temperature to 850 K. The high temperature regime is governed by an activated behavior with a frequency and sample independent activation energy of about 0.9 eV. The low temperature regime exhibits a frequency dependent and weakly temperature dependent conductivity due to extrinsic properties. Anomalies in the heating curves of virgin samples (dynamical vacuum conditions) in the temperature ranges 560 K and 740 K are ascribed to the desorption of oxygen.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 1432-0630
    Keywords: 33.50.Dq ; 71.35.+z ; 31.50.+w
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The highly excited state of fullerenes is characterised by a luminescence output which is dependent on the cube of the input intensity. This nonlinear emission is red shifted from the low-level emission and has a long, intensity dependent lifetime. Under similar irradiation conditions, the photoconductive response is seen to increase with the cube of the input intensity and the photocurrent in the highly excited state is observed to be largely independent of temperature, contrasting sharply with the thermally activated behaviour at low excitation densities. The degree of nonlinearity of the observed phenomena exclude an interpretation in terms of intra-molecular processes and the temperature dependence of the photoconductive response is suggestive of a Mott-like transition. The nonlinear behaviour is compared to that of indirect band-gap semiconductors in which the origin of similar nonlinear phenomena in the highly excited state luminescence and photoconductivity are explained in terms of electron-hole droplet formation. The similarities of the behaviours leads to a consideration of exchange and correlation energies in fullerenes, which are calculated according to a phenomenological model. Estimates of the contributions are consistent with a Mott-like transition at high excitation densities and an excess exchange/correlation energy in the highly excited state of ∼150 meV.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...