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  • 1
    Electronic Resource
    Electronic Resource
    The temperature dependence of the absorption coefficient of porous silicon (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 5978-5983 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The spectral behavior and the temperature dependence of the absorption coefficient of microporous silicon films are studied in the energy range of 1.2–3.8 eV, between 7 and 450 K. For photon energies above the direct band gap at 3.3 eV, the spectral behavior of the absorption coefficient is similar to that of crystalline silicon, and its absolute value is comparable to that estimated using Bruggeman effective medium approach. For lower energies the absorption coefficient is much reduced with respect to the effective medium model prediction. In this energy region, the absorption depends exponentially on the photon energy. From the temperature dependence of the absorption it is shown that this "Urbach tail''-like behavior is not due to absorption in surface states. In the range 300–400 K, the temperature dependence of the absorption coefficient of microporous and crystalline silicon is the same. This is a strong indication that phonon-assisted optical absorption takes place as expected from the indirect nature of crystalline silicon. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363595
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  • 2
    Electronic Resource
    Electronic Resource
    Strongly opalescent liquid network formed in a porous silicon matrix (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 4131-4135 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on a medium exhibiting extremely efficient light scattering properties: a liquid network formed in a porous silicon matrix. We find that the scattering efficiency depends strongly on the filling factor of the liquid in the pores, its dielectric constant, and the type of termination of the internal surface of the layer. The spectral dependence of the scattering length of photons evidences the fact that the phenomenon is governed by a Mie-type scattering mechanism. The mean free path of photons in this medium is found to be in the micrometer range. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1456249
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  • 3
    Electronic Resource
    Electronic Resource
    Highly sensitive recognition element based on birefringent porous silicon layers (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 3529-3532 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Anisotropically nanostructured silicon layers exhibit a strong in-plane birefringence. Their optical anisotropy parameters are found to be extremely sensitive to the presence of dielectric substances inside of the pores. Polarization-resolved transmittance measurements provide an extremely sensitive tool to analyze the adsorption of various atoms and molecules in negligible quantities. A variation of the transmitted linearly polarized light intensity up to two orders of magnitude combined with a fast optical response in the range of seconds make these layers a good candidate for sensor applications. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1391417
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  • 4
    Electronic Resource
    Electronic Resource
    Time-delayed luminescence from oxidized porous silicon after ultraviolet excitation (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 49-51 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Oxidized porous silicon is known to luminesce efficiently and with a ns-fast response in the green-blue region of the spectrum (2.3–2.7 eV) at room temperature. For microporous Si processed by rapid thermal oxidation at 1100–1200 °C in a dry oxygen ambient, we observe that the blue light has a time-delayed component that indicates carrier trapping. In addition to the well-established ultrafast light (∼1 ns) a signal with a time delay of order 1 s is present under UV photoexcitation. The time-delayed blue light exists at low temperature and has an excitation onset edge at 4.3±0.1 eV, an energy that is usually associated with a band discontinuity at the Si–SiO2 interface. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114178
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  • 5
    Electronic Resource
    Electronic Resource
    Fast and slow visible luminescence bands of oxidized porous Si (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 214-216 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The visible luminescence of porous Si is known to contain at least two spectrally distinct emission bands with widely different response times. The orange-red luminescence component (1.5–1.9 eV) decays in times being of the order of 10 μs at room temperature. The blue-green band (2.3–2.6 eV) is very much faster with response time in the 10-ns range. It is shown that with increasing degree of oxidation the fraction of the fast luminescence intensity rises from ∼1% of the total in the as-prepared porous Si to become the dominant spectral component in strongly oxidized material. For the rapid-thermal-oxidized material excited with 337-nm radiation, the intensity of the fast luminescence is comparable to that in the as-prepared state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111508
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  • 6
    Electronic Resource
    Electronic Resource
    Porous Si anisotropy from photoluminescence polarization (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 1585-1587 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the observation of the anisotropic linear polarization of porous Si photoluminescence measured in two excitation geometries. In the normal excitation geometry (exciting beam normal to the sample (100) surface) linear luminescence polarization of as much as 20% is seen parallel to the excitation polarization. In the edge excitation geometry (exciting light incident on a cleaved edge of the sample) the luminescence polarization is aligned mainly in the [100] direction (normal to the surface). The effect is described within the framework of a dielectric model in which porous Si is considered as an aggregate of slightly deformed, elongated and flattened, dielectric elliptical Si nanocrystals with preferred orientation in the [100] direction. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114947
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  • 7
    Electronic Resource
    Electronic Resource
    Resonant two-photon excitation of silicon nanocrystals (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 3350-3352 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied generation of visible photoluminescence (PL) in porous silicon (PSi) under resonant two-photon excitation. While the temporal decays of the resonant photoluminescence excited by one- and two-photon absorption are identical and show the same temperature dependence, the PL response differs significantly near the excitation energy. Contrary to one-photon excitation, no spectral gap between the excitation energy and the onset of the two-photon excited PL is observed. This is explained in the framework of selection rules for dipole allowed and forbidden optical exciton transitions in silicon nanocrystals. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123341
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  • 8
    Electronic Resource
    Electronic Resource
    Control of silicon nanocrystallite shape asymmetry and orientation anisotropy by light-assisted anodization (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 1116-1118 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is shown that the different and conflicting results on the strength of polarization memory effect on porous Si result from the influence of light on the electrochemical etching process. Illumination in general reduces the memory effect by decreasing the particle shape asymmetry. Linearly polarized light can both enhance or reduce the effect. It is accompanied by an in-plane orientation anisotropy of the memory parameter for (100) porous Si. This effect is evidence for a preferential alignment of the crystallite asymmetry axis normal to the light polarization. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.118502
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  • 9
    Electronic Resource
    Electronic Resource
    Luminescence of porous silicon in a weak confinement regime (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 1107-1109 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on luminescence properties of porous silicon emitting efficient light only a few tens of meV above the band gap of bulk Si. This emission band has a well-defined low-energy limit coincident with the position of the lowest possible luminescing exciton state of bulk silicon. The resonant photoluminescence spectrum exhibits all possible combinations of zero-phonon and momentum-conserving TA- and TO-phonon assisted absorption and exciton emission processes known for bulk silicon. We found that TO-phonon assisted processes give a major contribution to the light emission. We discuss the implications of these studies for the understanding of the origin of porous silicon photoluminescence. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122099
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  • 10
    Electronic Resource
    Electronic Resource
    Strong in-plane birefringence of spatially nanostructured silicon (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 916-918 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on a strong intrinsic optical anisotropy of Si induced by its dielectric patterning. As a result, an in-plane birefringence for nanostructured (110) Si surfaces is found to be 104 times stronger than that observed in bulk silicon crystals. We found the value of birefringence to be strongly dependent on the dielectric surrounding of the silicon nanoparticles assembling these layers. Beyond numerous potential implications for realization of optical devices and sensors, this gives a favorable route for studying the physics of condensation phenomena in a mesoscopic geometrical scale. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1343476
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