We present first-principles calculations of structural, electronic, magnetic, and optical propert... more We present first-principles calculations of structural, electronic, magnetic, and optical properties of zigzagoriented silicene nanoribbons, which, being endowed with spin-polarized edge states, are promising candidates as building blocks of future spintronic devices. The minimal width for a structurally stable planar structure having zigzag edges corresponds to a 4-chain ribbon, whose ground state presents antiferromagnetically coupled spin-polarized edges, and a lattice parameter along the nanoribbon axis contracted (∼5%) with respect to the bulk value. Starting from the dependence of structural and electronic properties on the ribbon width, we present theoretical predictions for the optical spectra of narrow nanoribbons, in which excitonic effects are relevant due to the confinement in a quasi-one-dimensional structure. Especially for light polarized parallel to the ribbon axis, we find significant differences in the position of optical absorption peaks of ribbons with ferroor antiferromagnetically coupled edges, showing that optical spectra can be used as a fingerprint of the magnetic coupling of electronic edge states.
Bi 4Àx La x)Ti 3 O 12 (abbreviated as BLT) thin films were prepared by Sol-Gel processing method ... more Bi 4Àx La x)Ti 3 O 12 (abbreviated as BLT) thin films were prepared by Sol-Gel processing method with the initial materials of bismuth nitrate (Bi(NO 3) 3 Á5H 2 O), lanthanum nitrate (La(NO 3) 3 Á6H 2 O), and tetrabutyl titanate ((C 4 H 9 O) 4 Ti). The X-ray diffraction (XRD), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) studies were performed for determining the change of the crystal lattice constant, the surface morphology, the chemical composition of the films, and the chemical bonding energy of the ions in the films. It was found that BLT thin films have high c-axis orientation with monoclinlic structure, and the crystal lattice constants of the films are different from those reported in the literature. The a and b values of the lattice remain constant, but the c value reduces with an increasing lanthanum content x. The chemical composition of the films, and chemical bonding energy of bismuth and lanthanum ions in the near surface region are different from those in the inside region of the films. The films are bismuth enriched in the surface region, and the composition in the ''bulk'' region is agreement with the stoichiometry.
A defect chemical model for the behavior of acceptor-doped LaCrO3 as a function of oxygen pressur... more A defect chemical model for the behavior of acceptor-doped LaCrO3 as a function of oxygen pressure is proposed. This is considered within the regime that corresponds to oxygen deficit oxygen. The mathematical approach allows us to calculate the oxygen partial pressure dependant properties of La1−xSrxCr O3−δ in the range 0.10 ≤ x ≤ 0.30. The results show that the conductivity was independent of pO2 and was proportional to the dopant concentration at high pO2. Therefore, under reducing conditions, the conductivity decreased exponentially with decreasing pO2 and asymptotically approached a pO 1/4 2 relationship. Stability regimes and compensation mechanisms at various oxygen partial pressures and temperatures are proposed. This model also examines the charge compensation mechanisms that dominate under the different regimes and their implications for transport properties. From equilibrium constants, thermodynamic quantities such as standard enthalpy and entropy change for the defect formation reactions were calculated.
We present first-principles calculations of structural, electronic, magnetic, and optical propert... more We present first-principles calculations of structural, electronic, magnetic, and optical properties of zigzagoriented silicene nanoribbons, which, being endowed with spin-polarized edge states, are promising candidates as building blocks of future spintronic devices. The minimal width for a structurally stable planar structure having zigzag edges corresponds to a 4-chain ribbon, whose ground state presents antiferromagnetically coupled spin-polarized edges, and a lattice parameter along the nanoribbon axis contracted (∼5%) with respect to the bulk value. Starting from the dependence of structural and electronic properties on the ribbon width, we present theoretical predictions for the optical spectra of narrow nanoribbons, in which excitonic effects are relevant due to the confinement in a quasi-one-dimensional structure. Especially for light polarized parallel to the ribbon axis, we find significant differences in the position of optical absorption peaks of ribbons with ferroor antiferromagnetically coupled edges, showing that optical spectra can be used as a fingerprint of the magnetic coupling of electronic edge states.
Bi 4Àx La x)Ti 3 O 12 (abbreviated as BLT) thin films were prepared by Sol-Gel processing method ... more Bi 4Àx La x)Ti 3 O 12 (abbreviated as BLT) thin films were prepared by Sol-Gel processing method with the initial materials of bismuth nitrate (Bi(NO 3) 3 Á5H 2 O), lanthanum nitrate (La(NO 3) 3 Á6H 2 O), and tetrabutyl titanate ((C 4 H 9 O) 4 Ti). The X-ray diffraction (XRD), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) studies were performed for determining the change of the crystal lattice constant, the surface morphology, the chemical composition of the films, and the chemical bonding energy of the ions in the films. It was found that BLT thin films have high c-axis orientation with monoclinlic structure, and the crystal lattice constants of the films are different from those reported in the literature. The a and b values of the lattice remain constant, but the c value reduces with an increasing lanthanum content x. The chemical composition of the films, and chemical bonding energy of bismuth and lanthanum ions in the near surface region are different from those in the inside region of the films. The films are bismuth enriched in the surface region, and the composition in the ''bulk'' region is agreement with the stoichiometry.
A defect chemical model for the behavior of acceptor-doped LaCrO3 as a function of oxygen pressur... more A defect chemical model for the behavior of acceptor-doped LaCrO3 as a function of oxygen pressure is proposed. This is considered within the regime that corresponds to oxygen deficit oxygen. The mathematical approach allows us to calculate the oxygen partial pressure dependant properties of La1−xSrxCr O3−δ in the range 0.10 ≤ x ≤ 0.30. The results show that the conductivity was independent of pO2 and was proportional to the dopant concentration at high pO2. Therefore, under reducing conditions, the conductivity decreased exponentially with decreasing pO2 and asymptotically approached a pO 1/4 2 relationship. Stability regimes and compensation mechanisms at various oxygen partial pressures and temperatures are proposed. This model also examines the charge compensation mechanisms that dominate under the different regimes and their implications for transport properties. From equilibrium constants, thermodynamic quantities such as standard enthalpy and entropy change for the defect formation reactions were calculated.
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Papers by Ilham Chadli