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Article Citation - WoS: 6Citation - Scopus: 6Physical Properties of the Bi1.5zn0.92-2x< Solid Solutions(Elsevier Sci Ltd, 2016) Al Garni, S. E.; Qasrawi, A. F.; Mergen, A.The Hf doping effect on the structural, compositional, optical, electrical and dielectric properties of the bismuth-zinc-niobium oxide pyrochlore ceramics is explored by means of scanning electron microscopy, energy dispersive X-ray spectroscopy, ultraviolet-visible light spectroscopy in the wavelength range of 200-1100 nm, temperature dependent electrical resistivity measurements in the range of 300-460 K and dielectric spectroscopy in the frequency range of 0.1-1.0 GHz. The optimum solubility limit in the Bi1.5Zn0.92-2xHfxNb1.5O6.92 solid solution is observed for the Hf content of 0.06. Increasing the Hf content from 0.03 to 0.06 decreased the room temperature, lattice constant, strain, dislocation density, optical energy band gap and electrical resistivity. It also increased the crystallite size and the dielectric constant. The energy band gap of the pure BZN (3.30 eV) decreased to 2.21 and reached 2.10 eV as the Hf content increased from 0.03 to 0.06. This behavior of the BZN suggests its suitability for optical applications of the visible region of light like photovoltaic devices. In addition, the remarkable increase in the dielectric constant from 258 to 280 and 456 nominates the Hf doped pyrochlore for passive mode operation devices like microwave capacitors. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.Article Citation - WoS: 3Citation - Scopus: 3Optical Analysis of Ge/Mgo and Ge/Bn Thin Layers Designed for Terahertz Applications(Elsevier Sci Ltd, 2015) Al Garni, S. E.; Qasrawi, A. F.In this work, a 200 nm Ge thin film is used as a substrate to design Ge/MgO and Ge/BN layers. The optical dynamics in these devices are investigated by means of the reflectivity and the transmissivity measurements. Particularly, the details of the dielectric spectra and the values of the energy band gaps (E-g) are investigated. Below 350 THz, the construction of Ge/MgO and Ge/BN interfaces decreased the effective dielectric constant of Ge by 39% and by 76%, respectively. It also increased the quality factor of the Ge optical device from 150 to 1400 and to 940 at 300 THz. All the dispersive optical parameters are also evaluated. In addition, the direct/indirect E-g value of Ge which was determined as 1.15/0.72 eV is observed to shift down by a 0.13/0.42 and by a 023/0.54 eV for the Ge/MgO and Ge/BN devices, respectively. The sharp increase in the dielectric constant with decreasing frequency in the range of 353 273 THz, the dispersive optical parameters and the energy band gap attenuations of the optical structures are promising as they indicate the applicability of the Ge, Ge/MgO and Gel BN layers in terahertz sensing. The latter technology has a wide range of applications like medical and telecommunication devices. (C) 2014 Elsevier Ltd. All rights reserved.
