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  • 1
    Electronic Resource
    Electronic Resource
    Oxygen defect center red room temperature photoluminescence from freshly etched and oxidized porous silicon (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 2671-2674 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electron spin resonance and photoluminescence experiments have been performed on freshly etched and oxidized porous silicon. Results indicate the presence of oxygen-related centers (nonbridging oxygen-hole center clusters), which consist of similar core structures in as-made and oxidized porous silicon (PSi) samples. A direct correlation exists between the presence of these centers and a red photoluminescence observed in both freshly anodized and oxidized PSi, suggesting that this emission process is the result of optical transitions in the oxygen-hole centers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360716
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  • 2
    Electronic Resource
    Electronic Resource
    The EX defect center in porous silicon (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 2129-2131 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the observation of the EX center in porous silicon by electron spin resonance (ESR). This center has been previously observed in low temperature thin oxides on crystalline Si and is believed to comprise a delocalized hole on three or four oxygen dangling bonds at a Si vacancy. In porous Si the defect is seen only in samples which have been oxidized for a very short period of time (∼1 min). The ESR intensity of the EX center correlates with the red room-temperature photoluminescence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360761
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  • 3
    Electronic Resource
    Electronic Resource
    Wet oxidation of amorphous Si-Ge layer deposited on Si(001) at 800 and 900 °C (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 4020-4025 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Amorphous Si0.56G0.44 films were deposited on (001)Si by electron beam evaporation in a vacuum having a base pressure of 10−7 Torr. They were then wet oxidized at 800 and 900 °C in an open tube furnace for various times. Cross (x)-sectional and plan view transmission electron microscope techniques were employed to characterize the samples. At 800 °C, 30 min of wet oxidation produced a continuous polycrystalline Si-Ge layer, whereas 60 min of wet oxidation produced a discontinuous polycrystalline layer. After 100 min of wet oxidation at 800 °C, the Si-Ge layer was almost completely oxidized and no observable evidence of the epitaxial Si-Ge layer was found. Wet oxidation at 900 °C for 10 min produced a bilayer structure; one epitaxial and one polycrystalline layer separated by a contamination layer initially present on the substrate prior to deposition. A mostly epitaxial Si-Ge layer was obtained after 30 min of wet oxidation at 900 °C. These results will be discussed in terms of a previously suggested epitaxial growth model. The failure to obtain an observable epitaxial Si-Ge layer by wet oxidation at 800 °C will be discussed by consideration of changes in the kinetics and the stability of both SiO2 and GeO2 at this temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352255
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  • 4
    Electronic Resource
    Electronic Resource
    Study of the luminescence mechanism in porous silicon structures (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 407-413 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Measurements of n- and p-type porous silicon indicate no direct correlation between particle size and photoluminescence (PL) energy. Controlled continuous removal of silicon does not result in a continuous PL blueshift, which would be expected in the quantum confinement model. Also, high temperature (1200 °C) anneals of porous silicon lead to a material consisting of 100–200 nm silicon spheres, with very low dangling bond densities, similar to crystalline silicon. This material does not exhibit noticeable PL in the visible range but when dipped in hydrofluoric acid (HF) for 1 s, strong visible PL appears with no structural changes noted. Polysilane/hydride complexes appear with the HF treatment, leading to the conclusion that the visible PL may be the result of a surface phenomenon related to the polysilane/hydride complexes, and not to a bulk Si quantum confinement effect. Anneals of porous silicon to 690 °C also show a significant redshifting of the PL, exhibiting identical behavior to measurements of shrinking of the optical bandgap of hydrogenated amorphous silicon (a-Si:H). With these results in mind, a surface related polysilane luminescence mechanism in porous silicon will be discussed, in which the PL energy is a function of H content and the PL intensity is a function of total surface area.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353863
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  • 5
    Electronic Resource
    Electronic Resource
    The mechanism of epitaxial Si-Ge/Si heterostructure formation by wet oxidation of amorphous Si-Ge thin films (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 807-813 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial Si-Ge/Si heterostructures have been formed from amorphous Si0.86Ge0.14, Si0.7Ge0.3, and Si0.56Ge0.44 films which were deposited at a vacuum of 10−7 Torr, followed by a wet oxidation process. The presence of an initial native oxide precluded solid phase epitaxy under standard annealing conditions, but epitaxy could be achieved by the use of wet oxidation. The samples were oxidized for various times at 900 °C and examined in reflected electron diffraction, ellipsometry, and cross-sectional and plan-view transmission electron diffraction. The formation of the epitaxial layer has been examined, and an epitaxial growth model is suggested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345736
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  • 6
    Electronic Resource
    Electronic Resource
    Formation of epitaxial Si1−xGex films produced by wet oxidation of amorphous SiGe layers deposited on Si(100) (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 2483-2485 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial SiGe/Si structures have been formed by wet oxidation of amorphous SiGe films. Amorphous, 1000-A(ring)-thick Si0.86Ge0.14 films were electron beam evaporated onto RCA cleaned Si(100) substrates at a background pressure of 1×10−7 Torr. They were then wet oxidized in an open tube furnace, at 900 °C for various times. They have been examined by reflective high-energy electron diffraction and Rutherford backscattering. Results indicate the formation of an epitaxial SiGe layer following the oxidation, whereas a polycrystalline layer forms following a vacuum or nitrogen ambient anneal. It is suggested that the oxide contamination at the amorphous SiGe/Si interface is too high to allow solid phase epitaxial growth to occur in an oxygen-free ambient, but during the oxidation process, some native oxide is dissolved due to a gradient of silicon from the substrate to the growing SiO2 on the surface. This allows grains of the SiGe alloy to orient with respect to the substrate, and secondary grain growth occurs during the oxidation process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100220
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  • 7
    Electronic Resource
    Electronic Resource
    Interdiffusion measurements in asymmetrically strained SiGe/Si superlattices (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 2628-2630 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Interdiffusion measurements are reported for Si0.65Ge0.35/Si asymmetrically strained superlattices grown by molecular beam epitaxy at 530 °C. The temperature-dependent interdiffusion coefficient obtained from x-ray diffraction can be described by D=675 exp(−4.4 eV/kT)cm2/s in the temperature range 700–880 °C. Initially, an enhanced diffusion was observed, especially near the superlattice surface. This is attributed to the presence of nonequilibrium defects. Bulk interdiffusion measurements were made only after isoconfigurational conditions were attained. The diffusion analysis first formulated by J. W. Cahn [Acta Metall. 9, 795 (1961)] is applied here, and the relative importance of both gradient energy effects and coherency strain effects will be discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102858
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  • 8
    Electronic Resource
    Electronic Resource
    Growth and properties of scandium epitaxial films on GaN (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 3248-3250 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial scandium films have been grown on c-axis-oriented wurtzite GaN. The films are highly ordered, adherent, and reflective. For substrate temperatures in the range 640–780 °C an interfacial reaction yields a ScN layer whose thickness increases with temperature, consistent with Sc diffusion as the rate limiting step. Electrical contacts fabricated from the Sc/ScN/GaN films exhibit a 1.0 eV barrier height on n-type GaN. The Sc films, which represent a class of ductile materials, may constitute a compliant substrate for overgrowth of GaN. © 1996 American Institute of Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116563
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  • 9
    Electronic Resource
    Electronic Resource
    Real time observation of surface kinetics during the self-assembly of Ga chains on Si(112) (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 2355-2357 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Single wavelength reflectance difference anisotropy (RDA) has been used to study the kinetics of the self-assembly of Ga atom chains on faceted Si(112) surfaces. The formation of the chains is followed from the initial deposition through changes in the surface reconstruction from (5×1) to (6×1). We present a simple Monte Carlo model to account for the time evolution of the RDA signal as a function of temperature and experimentally determined kinetic parameters. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120428
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  • 10
    Electronic Resource
    Electronic Resource
    Light induced electron spin resonance in porous silicon (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 1245-1247 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the observation of a new metastable light induced defect center in porous silicon which has a g tensor with 〈110〉 symmetry and which is similar to the thermal donor, NL8, seen in thermally annealed Si. The optical response has an onset in the vicinity of the Si indirect band gap. The time dependence of the response has a sharp rise followed by a nearly saturated regime. Changing to a higher photon energy then results in another marked increase in the response. We suggest that this dependence of the absorption on excitation energy reflects the distribution of crystallite sizes. We observe that near ultraviolet light significantly bleaches the signal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112084
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