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ABSTRACT: Magneto-optical properties of ferromagnetic slanted columnar thin films from cobalt made by electron-beam glancing angle deposition are reported. Magneto-optic ellipsometry in the polar Kerr effect configuration was employed to determine the field- and wavelength-dependent complex magneto-optic polarizability parameter within the spectral range from 0.74 to 3.0 eV. Kerr effect measurements and calculations reveal a strong azimuthal dependence for the incident linear polarization with peak Kerr rotation one order of magnitude larger than what has been reported for solid Co thin films.
Applied Physics Letters 04/2010; · 3.84 Impact Factor
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ABSTRACT: The precise determination of materials' optical constants in the THz frequency domain is an important new challenge in basic research and is crucial for novel technological applications. Spectroscopic ellipsometry is known as a vital tool for the determination of the materials' dielectric function including its anisotropy. However, ellipsometric measurements at very long wavelengths are difficult due to the lack of reliable sources of sufficient intensity and brilliance. Here we report on our recent advances to use ellipsometry in combination with different electron beam based sources in order to in investigate condensed matter samples in the frequency range from 0.1 to 8 THz. We successfully employ terahertz radiation emitted from two different tunable desktop sources (Smith-Purcell-effect source and a backward wave oscillator) in a polarizer-sample-analyzer ellipsometer scheme. We discuss and present THz range physical material properties due to bound and unbound charge resonances in semiconducting materials. This research will provide important understanding of optical properties for novel materials, inspire new designs, and accelerate development of optical Terahertz devices.
MRS Proceedings. 12/2007; 1108.
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ABSTRACT: We report for the first time on the application of generalized ellipsometry at far-infrared wavelengths (wave numbers from 150 cm(-1) to 600 cm(-1)) for measurement of the anisotropic dielectric response of doped polar semiconductors in layered structures within an external magnetic field. Upon determination of normalized Mueller matrix elements and subsequent derivation of the normalized complex Jones reflection matrix r of an n-type doped GaAs substrate covered by a highly resistive GaAs layer, the spectral dependence of the room-temperature magneto-optic dielectric function tensor of n-type GaAs with free-electron concentration of 1.6 x 10(18) cm(-3) at the magnetic field strength of 2.3 T is obtained on a wavelength-by-wavelength basis. These data are in excellent agreement with values predicted by the Drude model. From the magneto-optic generalized ellipsometry measurements of the layered structure, the free-carrier concentration, their optical mobility, the effective-mass parameters, and the sign of the charge carriers can be determined independently, which will be demonstrated. We propose magneto-optic generalized ellipsometry as a novel approach for exploration of free-carrier parameters in complex organic or inorganic semiconducting material heterostructures, regardless of the anisotropic properties of the individual constituents.
Journal of the Optical Society of America A 03/2003; 20(2):347-56. · 1.56 Impact Factor
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Mathias Schubert,
Alexander Kasic,
Tino Hofmann,
Volker Gottschalch,
Juergen Off,
Ferdinand Scholz,
Eva Schubert,
Horst Neumann,
Ian J. Hodgkinson,
Matthew D. Arnold,
Wayne A. Dollase, Craig M. Herzinger
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ABSTRACT: A new global approach, called 'Generalized Ellipsometry', is now capable to characterize the optical and structural properties of general anisotropic layered systems, including absorption, and can be applied, in general, to determine the linear response tensor elements for wavelengths from the far IR to the deep UV. This technique enables new insights into physical phenomena of layered anisotropic mediums, and can provide precise structural and optical data of novel compound materials. Experimental results are presented for stibnite single crystals as example for an arbitrary biaxial absorbing material, a wurtzite GaN thin film with uniaxial anisotropy grown on sapphire, a spontaneously atomically ordered III-V semiconductor alloy thin film, and a sculptured titanium dioxide film with symmetrically dielectric tensor properties.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
06/2002;
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ABSTRACT: The optical constants of Ga 0.51 In 0.49 P have been determined from 0.8 to 5.0 eV using variable‐angle spectroscopic ellipsometry measurements at room temperature. The metal‐organic vapor‐phase‐epitaxy‐grown samples were x‐ray analyzed to confirm lattice matching to the GaAs substrate. The effects of the native oxide were numerically removed from the data to determine the intrinsic optical constants. This is important because the optical constants reported become generally useful for modeling multiple‐layer structures. A Kramers–Kronig analysis was used to reduce interference‐related fluctuations in the below‐gap refractive index. Near the band edge a mathematical form for excitonic absorption was included. Critical point energies were extracted using a numerical second‐derivative fitting algorithm. © 1995 American Institute of Physics.
Journal of Applied Physics 05/1995; · 2.17 Impact Factor
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ABSTRACT: We report on the application of generalized ellipsometry at far-infrared wavelengths (150–600 cm−1) for measurement of the anisotropic dielectric response of doped polar semiconductors in layered structures within an external magnetic field. Measurement of normalized Mueller matrix elements allows for independent determination of the free-charge-carrier parameters density, mobility and effective mass for semiconductor alloy materials in layered structures upon application of the Drude model, thereby dispensing with the need for electrical measurements. Examples reviewed here include n-type/i-type GaAs, n-type GaAs/n-type Al0.19Ga0.33In0.48P/i-type GaAs, and n-type B0.03In0.06Ga0.91As/i-type GaAs layer structures, measured at room-temperature and magnetic fields up to ±3 T.
Thin Solid Films.
