Prediction of optical properties of amorphous tetrahedrally bonded materials

Abstract

A new approach is described for the prediction of the optical properties of amorphous tetrahedrally bonded materials over the entire experimental energy range, in which a model of the imaginary part of the dielectric constant is assigned and the real part is obtained by the Kramers-Kronig transform. Tight-binding theory provides direct interpretation of the model parameters. The model provides good insight into the physics of the problem and a qGuantitative account of experimental data as well. Results are presented for Si, Ge, Si 3 N 4 , and aAs,

Analytic optical-constant model derived from Tauc-Lorentz and Urbach tail

“…The optical properties of various groups of materials in nature have common features; this allows the use of simple models to describe their optical constants in certain spectral ranges, which depend on few parameters to be determined for each material. Semiconductors is a group of materials for which various models have been developed to parameterize their optical constants, such as the models of Forouhi and Bloomer [1] (FB), Campi and Coriasso [2], Tauc-Lorentz [3] (TL), or Cody-Lorentz [4]. If we broaden the scope of materials and the spectral range, the model will need more parameters to fit.…”

Fabrication and current-voltage characterization of a ferroelectric lead zirconate titanate/AlGaN∕GaN field effect transistor

“…The voltage required for memory operation can be adjusted by choosing an appropriate thickness for the PZT layer for a given coercive field. Considering the dielectric constants of PZT ͑⑀ PZT = 520ϳ 1300͒, 26 Si 3 N 4 ͑⑀ Si 3 N 4 = 7.5͒, 27 and Al 0.3 Ga 0.7 N ⑀ Al 0.3 Ga 0.7 N = 8.7 ͑assumed to be linearly dependent on Al composition and to lie between 8.5 for AlN and 9.0 for GaN͒, 28 E PZT Ϸ 10.4ϳ 4.2 kV/ cm is calculated for V GS = ± 12 V, which is sufficient for the ferroelectric domain switching to occur in PZT. The ⌬I D as wide as possible, but consistent with the operating voltages desired, is necessary to store clear "0" or "1" information in the opposite direction of the hysteresis loop for the nonvolatile FRAM application, which may be achieved by further optimization of the PZT growth conditions, so as to improve the PZT crystallinity.…”

Temperature dependent dispersion models applicable in solid state physics

“…The high energy valence electron excitations can be modeled by dispersion models based on the combination of the Tauc's law with the Lorentz model [26], which are usually used for interband transitions. For example, the Campi-Coriasso [27] dispersion model is appropriate if accurate description in the X-ray region is not required. The Lorentz model has the classical asymptotic behavior for high energies which does not accurately describe scattering processes in the X-ray region (see discussion in [7]).…”

“…The normalized transition strength function of the disordered materials can be described using the models unifying all the valence electron excitations, ie interband transitions and the high energy excitations of valence electrons. The examples of such models are the Campi-Coriasso [27], Jellison-Modine [28,29] (known as the Tauc-Lorentz) or Ferlauto et al [30] (known as the Cody-Lorentz) models, which combine the Tauc's law and the Lorentz model [26]. We should note that for the purposes of our temperature dependent dispersion model it is necessary to perform the proper sum rule normalization of these models.…”