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Indium gallium oxide [(InxGa1−x)2O3] alloys are of interest for a variety opto-electronic applications including photovoltaic devices owing to the ability to control properties through alloy composition. A thorough evaluation of the opto-electronic properties of (InxGa1−x)2O3 (x = 0.71, 0.55, 0.45, 0.36, and 0.28) thin films is obtained by using terahertz to ultraviolet range spectroscopic ellipsometry to measure the complex dielectric function (ɛ = ɛ1 + iɛ2) spectra from 0.400 meV to 5.877 eV and the derived vibrational modes from chemical bonding, inter-band transition energies, and carrier transport properties. Optical band edges of direct and non-direct transitions increase from 3.82 to 4.14 eV and 2.96 to 3.36 eV, respectively, with decreasing In-content, whereas the carrier concentration determined from the direct electrical Hall effect and spectroscopic ellipsometry measurements decreases from ∼1020 to 1018 cm−3. Mobilities (μSE), resistivities (ρSE), and carrier effective masses (m*SE) from the spectroscopic ellipsometry range from ∼10.6 to ∼66.8 cm2 V−1 s−1, 2.3 × 10−3, to 47.1 × 10−3 Ω cm, and 0.308 to 0.397 me, respectively. μSE and ρSE are compared to those obtained from the direct electrical Hall effect and four-point probe measurements with discrepancies attributed to principles of measurement techniques. Spectroscopic ellipsometry determined parameters are representative of properties within localized regions, whereas direct electrical measurements are influenced by a greater degree of charge carrier scattering due to longer path lengths of travel. [ABSTRACT FROM AUTHOR]

Generalized ellipsometry measurements are used to extract the complex dielectric function (ε = ε 1 + i ε 2) spectra of GdScO3 single crystals over the 0.7–8.5 eV photon energy range. GdScO3 is a wide bandgap semiconductor with a high dielectric constant, and potential applications include replacing SiO2 in silicon-based transistors and as an epitaxial substrate for thin film growth. This work presents the anisotropic optical properties for electric fields oscillating parallel to the a-, b-, and c-crystallographic axes. A direct bandgap is identified at 6.44 eV along the direction parallel to the a-axis, with additional critical points observed at 6.74 and 7.42 eV in the same direction. Additional above gap critical point transitions are found at 6.72, 7.31, and 7.96 along the direction parallel to the b-axis and 6.83 and 8.00 eV along the direction parallel to the c-axis. [ABSTRACT FROM AUTHOR]

Generalized ellipsometry measurements are used to extract the complex dielectric function (ε = ε 1 + i ε 2) spectra of GdScO3 single crystals over the 0.7–8.5 eV photon energy range. GdScO3 is a wide bandgap semiconductor with a high dielectric constant, and potential applications include replacing SiO2 in silicon-based transistors and as an epitaxial substrate for thin film growth. This work presents the anisotropic optical properties for electric fields oscillating parallel to the a-, b-, and c-crystallographic axes. A direct bandgap is identified at 6.44 eV along the direction parallel to the a-axis, with additional critical points observed at 6.74 and 7.42 eV in the same direction. Additional above gap critical point transitions are found at 6.72, 7.31, and 7.96 along the direction parallel to the b-axis and 6.83 and 8.00 eV along the direction parallel to the c-axis. [ABSTRACT FROM AUTHOR]

Complex dielectric function (ɛ = ɛ1 + iɛ2) spectra are obtained from reflection mode spectroscopic ellipsometry and unpolarized transmittance measurements for 4H and 6H stacking sequence silicon carbide (SiC) nitrogen-doped single crystals from the infrared (IR) to vacuum ultraviolet (VUV) spectral range. A single parametric model describing ɛ predominately for the ordinary directions is developed over the 0.05–8.5 eV spectral range from analysis of (0001)-oriented back side roughened 4H-SiC and 6H-SiC single crystals with some contribution from the extraordinary direction of 6H-SiC in the IR region. Indirect bandgaps for 4H-SiC and 6H-SiC are found to be 3.30 and 3.03 eV, respectively, and the corresponding direct optical gaps are at 4.46 and 4.42 eV. A model describing the optical response in the IR spectral range is created using a Drude expression and either transverse optical (TO) and longitudinal optical (LO) (TOLO) or Lorentz oscillator models. Free carrier concentration (N) is optically measured to be 3.7 × 1018 and 3.3 × 1018 cm−3 using TOLO and Lorentz oscillator models, respectively, and the corresponding carrier mobility (μ) is 34 and 39 cm2/V s for 4H-SiC. Under the same assumption for 6H-SiC, N is measured to 8 × 1018 cm−3 using either TOLO or Lorentz oscillator models and μ is 9 and 10 cm2/V s using the TOLO and Lorentz oscillator models, respectively, in the ordinary direction and 5 cm2/V s in the extraordinary direction using either model. For 4H-SiC, using the TOLO oscillator model, TO and LO phonon modes are measured at 797.7 and 992.1 cm−1, respectively, and corresponding modes are found at same locations using the Lorentz oscillator model. In 6H-SiC, using the TOLO model, TO modes in ordinary and extraordinary directions are found at 797.7 and 789.7 cm−1, and corresponding modes are at 796.9 and 788.9 cm−1 using the Lorentz oscillator model. The LO modes using the TOLO model are found at 992 and 984 cm−1 in the ordinary and extraordinary directions, respectively, and the same modes in the corresponding direction using the Lorentz oscillator model are located at 975.9 and 967.9 cm−1. [ABSTRACT FROM AUTHOR]

Complex dielectric function (ɛ = ɛ1 + iɛ2) spectra of a heat treated single crystal yttria-stabilized zirconia (YSZ) have been determined over a spectral range of 0.03–8.5 eV using spectroscopic ellipsometry. Spectra are collected using three instruments covering different parts of the measured spectrum. The YSZ sample is modeled as a semi-infinite bulk crystal covered by a surface layer described by a Bruggeman effective medium approximation of equal parts YSZ and void. [ABSTRACT FROM AUTHOR]

TbScO3 is a wide bandgap semiconductor with potential applications in charge trap memory devices and acts as an alternate gate dielectric in fully depleted transistors and also a substrate for epitaxial thin film growth. TbScO3 has an orthorhombic crystal structure, which gives rise to optical anisotropy. Generalized ellipsometric spectra are measured for multiple in-plane rotations of (110) and (001) oriented TbScO3 single crystals over a photon energy range of 0.7–8.5 eV to determine the complex dielectric function (ε = ε1 + iε2) spectra for electric fields oscillating along each axis. A direct bandgap is identified at 6.50 eV, and above gap critical point transitions are found at 6.99, 7.14, 7.16, 7.21, and 7.42 eV. [ABSTRACT FROM AUTHOR]

TbScO3 is a wide bandgap semiconductor with potential applications in charge trap memory devices and acts as an alternate gate dielectric in fully depleted transistors and also a substrate for epitaxial thin film growth. TbScO3 has an orthorhombic crystal structure, which gives rise to optical anisotropy. Generalized ellipsometric spectra are measured for multiple in-plane rotations of (110) and (001) oriented TbScO3 single crystals over a photon energy range of 0.7–8.5 eV to determine the complex dielectric function (ε = ε1 + iε2) spectra for electric fields oscillating along each axis. A direct bandgap is identified at 6.50 eV, and above gap critical point transitions are found at 6.99, 7.14, 7.16, 7.21, and 7.42 eV. [ABSTRACT FROM AUTHOR]

We have studied the growth of epitaxial films of stannate pyrochlores with a general formula A2Sn2O7 (A = La and Y) and find that it is possible to incorporate ∼25% excess of the A-site constituent; in contrast, any tin excess is expelled. We unravel the defect chemistry, allowing for the incorporation of excess A-site species and the mechanism behind the tin expulsion. An A-site surplus is manifested by a shift in the film diffraction peaks, and the expulsion of tin is apparent from the surface morphology of the film. In an attempt to increase La2Sn2O7 conductivity through n-type doping, substantial quantities of tin have been substituted by antimony while maintaining good film quality. The sample remained insulating as explained by first-principles computations, showing that both the oxygen vacancy and antimony-on-tin substitutional defects are deep. Similar conclusions are drawn on Y2Sn2O7. An alternative n-type dopant, fluorine on oxygen, is shallow according to computations and more likely to lead to electrical conductivity. The bandgaps of stoichiometric La2Sn2O7 and Y2Sn2O7 films were determined by spectroscopic ellipsometry to be 4.2 eV and 4.48 eV, respectively. [ABSTRACT FROM AUTHOR]