Papers by Keyword: Optical Conductivity

Abstract: The review article focuses on the growth of thin film and its characterization by UV-Vis-NIR spectroscopy. For UV-Vis-NIR spectroscopy of thin films, they are usually deposited on translucent quartz glass surfaces. The article reports the extraction of various thin film optical parameters viz., absorption coefficient (α), Urbach energy (E_u), optical band gap (E_g), refractive index (n), extinction coefficient (k), dielectric constants, dissipation factor (tanδ) and optical conductivity (σ_optical) by using optical spectra (absorption(A)/transmittance (T)/reflectance (R)). Furthermore, the effect of thin film substrate temperature (T_s) and/or thickness (d) and/or post-deposition annealing temperature (T_a) on various optical parameters is discussed in detail.

Abstract: The aim of this study is to determine the optical parameters of the ternary alloys LaNi_4.5M_0.5 (M=Al, Mn) by using first-principles calculations. Through the computer simulation, we have successfully obtained the absorption coefficient, optical conductivity and dielectric function of these alloys. These alloys are transparent for the electromagnetic waves with frequencies of 12eV~15eV. The calculated dielectric constants are 188.3 and 257.6 for LaNi_4.5Al_0.5 and LaNi_4.5Mn_0.5, respectively. Our result is compared with the previous study and a good agreement is found.

Abstract: We Review Our Dynamical Property Measurements of Rattling Phonons in Type-I Clathrate Compounds, the Quasi-on-Center Ba₈Ga₁₆Ge₃₀ (BGG) and Off-Center Ba₈Ga₁₆Sn₃₀ (BGS), Using a Terahertz Time-Domain Spectrometer. The Lowest-Lying Vibrational Modes of Rattling Ba Ions in the Oversized Cage Show Anomalous Temperature Dependence in their Spectra. For BGG, the Temperature Dependence Is Mostly Consistent with a Local Anharmonic Potential Approximation that Predicts Softening towards Low Temperature. On the other Hand, for BGS, a Single Broad Peak of Off-Center Rattling Phonons Splits into Two Subpeaks below 120 K, and, with Further Lowering Temperature, the Spectra Show Anomalous Broadening. While the Splitting Can Be Understood by the Double Well Potential, the Linewidth Broadening Must Be Attributed to some Relevant Interactions with such Excitations as Acoustic Phonons and Doped Carriers.

Abstract: Optical properties of the LaNi5-xCux (x = 0, 0.6, 1, 1.2) compounds were studied. It was shown that substitution of copper for nickel led to noticeable changes in the optical conductivity spectra. Calculations of the electronic structure of compounds with x = 0, 1, 2 were performed using a generalized gradient approximation. The interband optical conductivity of these intermetallics was calculated. The optical ellipsometrical measurements and theoretical calculations testify to the appearance of a broad absorption structure associated with the Cu 3d  Ni 3d electron transitions and increasing with the growth of copper content.

Abstract: Magnetic, electronic, structural and magnetovolume properties of the R2Fe17-xMx (R = Y, Lu, Ce; M = Si or Al) compounds were studied. We pioneered to apply electronic band parameters determination to account for the anomalous volume dependence of ferromagnetism in these compounds.