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  • 1
    Electronic Resource
    Electronic Resource
    Quantum-confinement effects in CdTe-glass composite thin films produced using rf magnetron sputtering (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 1218-1224 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Quantum-confinement-induced shifts in the fundamental absorption edge of isolated CdTe crystallites are reported in CdTe-glass composite thin films produced using a sequential rf magnetron sputtering process employing two separate sputtering sources. Films ranging in thickness from 0.5 to 4.5 μm and containing as much as 30 vol % CdTe have been produced, illustrating the versatility of this technique over a more conventional melting approach. Post-deposition heat treatments were used to produce average crystallite sizes in the range 46–158 A(ring). An improved fit to theory at larger crystal sizes is found if a cylindrical crystal morphology is assumed. The effective mass of the confined specie, which governs the shift of the absorption edge with crystal size, is found to be 0.20m0 (spherical morphology) and 0.12m0 (cylindrical morphology), both of which are greater than the exciton-reduced mass in bulk CdTe. The data suggests, therefore, that a non-negligible Coulomb interaction may still exist in crystals even as small as 0.31 times the size of the bulk Wannier exciton diameter. Planar waveguiding has also been demonstrated in these samples as a preliminary step to the production of waveguide-based nonlinear device structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346720
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  • 2
    Electronic Resource
    Electronic Resource
    Monte Carlo simulation of ferroelectric domain structure and applied field response in two dimensions (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 4415-4424 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A two-dimensional, lattice-Monte Carlo approach, based upon the energy minimization of an ensemble of electric dipoles, was developed to simulate ferroelectric domain behavior. The model utilizes a Hamiltonian for the total energy based upon electrostatic terms involving dipole–dipole interactions, local polarization gradients, and the influence of applied electric fields. The impact of boundary conditions on the domain configurations obtained was also examined. In general, the model exhibits domain structure characteristics consistent with those observed in a tetragonally distorted ferroelectric. The model was also extended to enable the simulation of ferroelectric hysteresis behavior. Simulated hysteresis loops were found to be very similar in appearance to those observed experimentally in actual materials. This qualitative agreement between the simulated hysteresis loop characteristics and real ferroelectric behavior was also confirmed in simulations run over a range of simulation temperatures and applied field frequencies. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373086
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  • 3
    Electronic Resource
    Electronic Resource
    Quantum-size effects on the band edge of CdTe clusters in glass (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 8039-8045 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The measurement of quantum-size behavior in semiconductor crystals has been examined through an analysis of the size dependence of the semiconductor's absorption edge. In past studies, there appeared to be little agreement between theory and experiment for very small crystals. In this paper, the effects of crystal-size distribution and tunneling of the carrier wave functions into the quantum well barrier are considered. An analysis of the microstructure size and absorption edge of CdTe clusters in a glass matrix is conducted with samples ranging from 0.16 to 0.8 times the exciton Bohr diameter at the Γ point and from 1 to 5 times the exciton Bohr diameter at the L point. Results show fully coupled exciton behavior at the L point and a more complex process at the Γ point. In the latter, the band-gap energy increase with decreasing cluster size is significantly smaller than that calculated using a model in which the photoexcited carriers are assumed to be confined to a monosize set of clusters bounded by an infinite potential well. Analysis presented here shows that this discrepancy can be explained in part by inhomogeneous broadening of the absorptive transition and by carrier penetration into the insulator. The quantum-size behavior of CdTe crystals at the Γ point is subsequently found to follow fully decoupled carrier behavior modeled by Efros and Efros [Sov. Phys. Semicond. 16, 772 (1982)] when the inhomogeneous broadening and tunneling effects are taken into account.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356544
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  • 4
    Electronic Resource
    Electronic Resource
    Red photoluminescence and optical absorption in hydrogen-treated GeO2-SiO2 sol-gel-derived planar waveguides (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 2537-2539 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the effects of post-deposition, reducing atmosphere heat treatment on the optical absorption, and photoluminescence response of 45 GeO2-55 SiO2 thin films produced using the sol-gel process. With increasing heat treatment, a linear increase in the 242 nm absorption peak (associated with oxygen-deficient germania centers) is found to contrast a reduction in the intensity of red photoluminescence (attributed to hydrogen centers in the glass structure). These results are discussed in terms of the photosensitive response of these materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111566
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  • 5
    Electronic Resource
    Electronic Resource
    Electro-optical characterization of Pb(Zr,Ti)O3 thin films by waveguide refractometry (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 2180-2182 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electric field-induced changes in the extraordinary and ordinary refractive indices of a Pb(Zr0.53Ti0.47)O3 thin film were independently determined using waveguide refractometry. Under an electric field, applied normal to the film plane and corresponding to saturation of the electric polarization, the ratio of the extraordinary to ordinary refractive index change (Δne/Δno) is found to be −4/1, contributing to a net birefringence change [Δ(ne-no)] of −0.021. Using this technique, both diagonal and off-diagonal elements of the electro-optic response tensor describing the macroscopic behavior of the polycrystalline film were accessed, illustrating the importance of this approach in evaluating orientation-specific electro-optic characteristics in these films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.110576
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  • 6
    Electronic Resource
    Electronic Resource
    Charge trapping, isolated Ge defects, and photosensitivity in sputter deposited GeO2:SiO2 thin films (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 1453-1455 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nature of the defects in sputter-deposited GeO2:SiO2 thin films and their relationship to charge trapping and enhanced photosensitivity have been studied using electron paramagnetic resonance, capacitance–voltage, and optical bleaching and absorption spectroscopies. We find a good qualitative agreement between the density of isolated Ge dangling bonds measured magnetically, the density of charge trapping sites measured electrically, and the density of absorbing centers measured optically. Collectively, all observations can be modeled by assuming that a change in spin state and charge state of isolated paramagnetic neutral Ge dangling bonds, to form either diamagnetic positively or negatively charged Ge sites, are largely responsible for the charge trapping and photosensitivity in these thin films. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117612
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