arXiv subjects

L. M. R. Scolfaro

Publications and source records attributed to L. M. R. Scolfaro.

5 recordsLinked to original sources

arXiv2012

Effective masses and complex dielectric function of cubic HfO2

The electronic band structure of cubic HfO2 is calculated using an it ab initio all-electron self--consistent linear augmented plane-wave method, within the framework of the local-density approximation and taking into account full-relativistic contributions. From the band structure, the carrier effective masses and the complex dielectric function are obtained. The Γ-isotropic heavy and light electron effective masses are shown to be several times heavier than the electron tunneling effective mass measured recently. The imaginary part of the complex dielectric function ε_2(ω) is in good agreement with experimental data from ultraviolet spectroscopic ellipsometry measurements in bulk yttria-stabilized HfO2 as well as with those performed in films deposited with the tetrakis diethylamido hafnium precursor for energies smaller than 9.5 eV.

cond-mat.mtrl-sci↗

arXiv2012

Band structure derived properties of HfO2 from first principles calculations

The electronic band structures and optical properties of cubic, tetragonal, and monoclinic phases of HfO2 are calculated using the first-principles linear augmented plane-wave method, within the density functional theory and generalized gradient approximation, and taking into account full-relativistic contributions. From the band structures, the electron- and hole-effective masses were obtained. Relativistic effects play an important role, which is reflected in the effective masses values and in the detailed structure of the dielectric function. The calculated imaginary part of the dielectric function and refractive index are in good agreement with the data reported in the literature.

cond-mat.mtrl-sci↗

arXiv2012

Structural, electronic, and optical properties of ZrO2 from ab initio calculations

Structural, electronic, and optical properties for the cubic, tetragonal, and monoclinic crystalline phases of ZrO2, as derived from it ab initio full-relativistic calculations, are presented. The electronic structure calculations were carried out by means of the all-electron full potential linear augmented plane wave method, within the framework of the density functional theory and the local density approximation. The calculated carrier effective masses are shown to be highly anisotropic. The results obtained for the real and imaginary parts of the dielectric function, the reflectivity, and the refraction index, show good agreement with the available experimental results. In order to obtain the static dielectric constant of ZrO2, we added to the electronic part, the optical phonons contribution, which leads to values of e1(0)~29.5, 26.2, 21.9, respectively along the xx, yy, and zz directions, for the monoclinic phase, in excellent accordance with experiment. Relativistic effects, including the spin-orbit interaction, are demonstrated to be important for a better evaluation of the effective mass values, and in the detailed structure of the frequency dependent complex dielectric function.

cond-mat.mtrl-sci↗

arXiv2006

Frequency Dependence of the Dielectric Constants and of the Reflectivity for HfO2 and ZrO2 from First-Principles Calculations

We present, in this work, our theoretical results for the phonon dispersions and the frequency dependence of the reflectivities and the dielectric constants of ZrO2 and HfO2 in the monoclinic phase. The results show the importance of the lattice contribution for the evaluation of the static dielectric constant. Also, besides the anisotropy shown by these materials along the x and z directions, the zero frequency static dielectric constant decreases with the increasing pressure.

cond-mat.mtrl-sci↗

arXiv2004

Charge and spin distributions in GaMnAs/GaAs Ferromagnetic Multilayers

A self-consistent electronic structure calculation based on the Luttinger-Kohn model is performed on GaMnAs/GaAs multilayers. The Diluted Magnetic Semiconductor layers are assumed to be metallic and ferromagnetic. The high Mn concentration (considered as 5% in our calculation) makes it possible to assume the density of magnetic moments as a continuous distribution, when treating the magnetic interaction between holes and the localized moment on the Mn(++) sites. Our calculation shows the distribution of heavy holes and light holes in the structure. A strong spin-polarization is observed, and the charge is concentrated mostly on the GaMnAs layers, due to heavy and light holes with their total angular momentum aligned anti-parallel to the average magnetization. The charge and spin distributions are analyzed in terms of their dependence on the number of multilayers, the widths of the GaMnAs and GaAs layers, and the width of lateral GaAs layers at the borders of the structure.

cond-mat.other↗