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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 60 (1995), S. 601-606 
    ISSN: 1432-0630
    Keywords: 82.40.Tc ; 81.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Photoluminescence studies on porous silicon show that there are luminescence centers present in the surface states. By taking photoluminescence spectra of porous silicon with respect to temperature, a distinct peak can be observed in the temperature range 100–150 K. Both linear and nonlinear relationships were observed between excitation laser power and the photoluminescence intensity within this temperature range. In addition, there was a tendency for the photoluminescence peak to red shift at low temperature as well as at low excitation power. This is interpreted as indicating that the lower energy transition becomes dominant at low temperature and excitation power. The presence of these luminescence centers can be explained in terms of porous silicon as a mixture of silicon clusters and wires in which quantum confinement along with surface passivation would cause a mixing of Γ andX band structure between the surface states and the bulk. This mixing would allow the formation of luminescence centers.
    Type of Medium: Electronic Resource
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  • 2
    facet.materialart.
    Unknown
    In:  Other Sources
    Publication Date: 2019-07-12
    Description: An edge-on disk galaxy would act as a lens to produce two images which are aligned. Such a model would explain the observed features of Q0957 + 561A, and B. The third image is expected to be very faint and so neat to center of the lensing galaxy as to be unobservable.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Letters (ISSN 0004-6388); 25; 2 19
    Format: text
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  • 3
    Publication Date: 2019-07-12
    Description: Significant variations of the broad hydrogen emission lines in the QSO 0736 + 017 have been found. Between 1978 and 1980 the H-beta line intensity dropped by 40-percent, and between 1985 and 1986 it increased by more than 50 percent. The H-gamma line intensity underwent a larger fractional change. Line variations occurred in less than 1 yr after variations of the underlying continuum, indicating that a major part of the broad line emission originates in a region of 1 lt-yr or smaller if it is spherical.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 306; L67-L69
    Format: text
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