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  • Electronic Resource  (25)
  • 1
    Electronic Resource
    Electronic Resource
    Photo-assisted tuning of luminescence from porous silicon (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6365-6367 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A method is proposed to control the wavelength of visible photoluminescence (PL) from porous silicon (PS). This is based on the post-anodization illumination technique which employs a filtered light with various maximum cutoff photon energies. As the illumination time increases, the PL spectra shift toward the higher energy side. This blue shift tends to stop at the time when the PL peak energy becomes close to the cutoff photon energy. The emission wavelength can be controllably tuned in a wide spectral range by changing the cutoff filter. These results give us a strong indication that the visible PL of PS is closely related to interband excitation in Si nanocrystallites, not to some surface chemical compounds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355160
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  • 2
    Electronic Resource
    Electronic Resource
    Photointercalation characteristics of thin WO3 films (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 398-402 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoinduced proton injection properties of amorphous thin WO3 films have been studied for a cell of the form quartz glass/semitransparent Au/ethanol/WO3/indium-tin-oxide- coated glass. When the cell was illuminated with near-uv light through a quartz window under open circuit conditions, a definite reversible change was induced in the optical and electrical properties of WO3 films. On the basis of some experimental analyses, this effect is attributed to photointercalation (PI) of protons into WO3 films. It is also demonstrated that WO3-based PI cells efficiently operate as an erasable device for storage and modulation of optical information.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350722
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  • 3
    Electronic Resource
    Electronic Resource
    Electroluminescence with high and stable quantum efficiency and low threshold voltage from anodically oxidized thin porous silicon diode (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 4319-4324 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Highly efficient electroluminescence (EL) is obtained at low operating voltage (〈5 V) from n+-type silicon-electrochemically oxidized thin porous silicon–indium–tin–oxide junctions. Continuous wave external quantum efficiency greater than 1% and power efficiency of 0.37% have been achieved. Considerable reduction of leakage current accounts for the enhancement of EL efficiency upon oxidation. The EL time response ((approximate)30 μs) is slower than the photoluminescence one, due to slow electrical charging of porous silicon. No degradation of quantum efficiency is observed during operation and upon aging. This is attributed to the electrochemically grown oxide, which should provide a better surface passivation than the initial hydrogen coverage. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1290458
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  • 4
    Electronic Resource
    Electronic Resource
    Fabrication and characteristics of three-dimensionally buried porous silicon optical waveguides (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 5274-5278 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A fabrication technology of three-dimensionally buried porous silicon (PS) optical waveguide with an extremely high refractive index contrast is presented, including its fundamental properties. The origins of attenuation losses are investigated by experimental and theoretical analyses in terms of microscopic observations, edge emission measurements, polarization mode determination of guided wave, and evaluation of bending loss. The results of these studies indicate that attenuation losses in PS waveguides are due to self-absorption by residual silicon, structural and optical inhomogeneities in the core region, and roughness at interfaces between the core and the cladding layers. Some possible ways for reducing these attenuation losses are discussed. It is also demonstrated that a buried bent PS waveguide with an extremely small curvature of 250 μm can be fabricated by simple planar processing, and that a visible optical wave propagates along it owing to a significantly high refractive index contrast between the core and the cladding layers. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371510
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  • 5
    Electronic Resource
    Electronic Resource
    Mechanism of the visible electroluminescence from metal/porous silicon/n-Si devices (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 1407-1412 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The excitation and radiative recombination mechanisms of carriers in electroluminescent porous silicon (PS) have been studied for the device with the structure of Au/PS/n-type Si. Experiments focus on the electroluminescence (EL) and photoluminescence (PL) spectra, the current-voltage-EL intensity relationship and its temperature dependence, and the excitation-wavelength dependence of the electric-field-induced PL quenching. The results of these experiments suggest the following points: (1) the EL occurs mainly near the Au/PS contact; (2) there exists an extremely high electric field at the Au/PS contact; (3) the EL originates from radiative recombination of strongly localized excitons; and (4) the radiative recombination rate is in proportion to the diode current. Based on these observations, an operation model is proposed. In our model, a large number of electrons and holes are generated in the PS layer by a field-assisted mechanism. Light emission occurs by radiative recombination of these electrons and holes via localized states. Because of field-enhanced carrier separation, however, the EL efficiency of this device is limited to a relatively low value of about 0.05%. Possible ways to improve the EL characteristics are discussed. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363878
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  • 6
    Electronic Resource
    Electronic Resource
    Photoelectronic properties of porous silicon (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 1986-1988 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is shown that the introduction of a porous structure into single-crystal Si produces substantial changes in the photoelectronic properties. The porous Si (PS) layer is formed by anodization of p-type Si wafers in a HF solution. The photoconduction cells used in this study consists of a semitransparent thin Au film, PS, Si substrate, and Al ohmic contact. The photoconductive behavior of PS is characterized by an extremely high dark resistivity, a definite photosensitivity for visible light, and an intrinsic bias voltage dependence of the spectral response. These properties, which are interpreted to be the result of a band-gap widening in PS, provide further support of the assumption that the visible luminescence of PS is explained by the band scheme.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357663
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  • 7
    Electronic Resource
    Electronic Resource
    Precisely tuned emission from porous silicon vertical optical cavity in the visible region (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 4841-4844 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The operating peak energy of a porous silicon (PS) cavity can be completely controlled over a wide range of 1.5–2.2 eV, using a PS-based Fabry–Perot resonator composed of a light-emitting active PS layer and two high-reflectivity mirrors. When the PS devices are excited by a uv laser, quite narrow spectra (10–40 meV in full width at half-maximum) are observed without any significant signs of side mode. The central photon energy is precisely and continuously tuned simply by changing the anodization parameters. The key issues of the controlled device operation are adjustment of the optical thickness of the active PS layer to an appropriate value and fabrication of the quarter-wavelength multilayered PS mirror with a high reflectivity. The spectral qualities of the emitted light are also discussed by theoretical analyses on the basis of a simplified model. These results suggest that the PS devices operate as sharp band-pass optical filter and the PS materials are available for novel silicon-based microphotonics. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363526
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  • 8
    Electronic Resource
    Electronic Resource
    Light-emissive nonvolatile memory effects in porous silicon diodes (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 93-95 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is demonstrated that there are distinct off and on states in the current–voltage characteristics of porous silicon (PS) diodes, and that the visible electroluminescence (EL) is observed in the on state. The PS diodes are composed of semitransparent thin Au films, rapid thermal oxidization (RTO)-treated PS layers (∼0.5 μm thick), p-type Si substrates, and ohmic back contacts. After the PS layers were prepared by anodizing Si wafers in an ethanoic HF solution, the samples were treated by RTO process. The bistable states of this PS diode can be simply and reversibly controlled by the external bias voltage. Based on the behavior of the EL and capacitance–voltage characteristics, the model of memory effect is presented, in which field-induced carrier injection and ejection into and from silicon nanocrystallites strongly affects the carrier transport. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122962
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  • 9
    Electronic Resource
    Electronic Resource
    Photointercalation effect of thin WO3 films (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 1324-1325 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is shown that thin amorphous films of WO3 exhibit a photoinduced reversible coloration in an electrochemical cell of the form quartz/semitransparent Au/ethanol/WO3/In2O3-coated glass. From measurements of the optical and electrical properties of the films, the coloration is attributed to the formation of HxWO3, presumably due to a photointercalation of protons into WO3 films. This effect is potentially useful for storage, learning, and modulation of two-dimensional optical information.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104231
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  • 10
    Electronic Resource
    Electronic Resource
    Activation of blue emission from oxidized porous silicon by annealing in water vapor (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 1776-1778 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is reported that annealing of oxidized porous silicon in water vapor at about 250 °C drastically enhances its blue emission. Infrared absorption studies indicate that this annealing increases all the absorption peaks related to O–H vibrations, except for that of free silanol which disappears completely. No traces of carbon-related signals are observed. The latter result makes a clear objection to blue-band luminescence models based on adsorbed carbon compounds. Although the possibility of silanol-related origins cannot be ruled out, we suggest that some passivation effect of adsorbed hydroxyls on Si nanostructures surrounded by SiO2 is also likely. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366899
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