A5077237202- Optical Coatings and Gratings
- Photonic and Optical Devices
- Photonic Crystals and Applications
- Semiconductor Quantum Structures and Devices
- Graphene research and applications
- GaN-based semiconductor devices and materials
- Quantum and electron transport phenomena
- ZnO doping and properties
- Terahertz technology and applications
- Metamaterials and Metasurfaces Applications
- Acoustic Wave Resonator Technologies
- Semiconductor materials and interfaces
- Nonlinear Optical Materials Studies
- Semiconductor materials and devices
- Magneto-Optical Properties and Applications
- Plasmonic and Surface Plasmon Research
- Magnetic properties of thin films
- Ga2O3 and related materials
- Optical Polarization and Ellipsometry
- Advanced Antenna and Metasurface Technologies
- Diamond and Carbon-based Materials Research
- Topological Materials and Phenomena
- Carbon Nanotubes in Composites
- Electronic and Structural Properties of Oxides
- Quantum Dots Synthesis And Properties
University of North Carolina at Charlotte
2016-2024
University of Nebraska–Lincoln
2010-2020
J.A. Woollam Company (United States)
2011-2020
Leibniz Institute of Polymer Research
2020
Linköping University
2015-2019
Optica
2016-2018
National University of Singapore
2015
Cornell University
2009
Leipzig University
1999-2006
We derive a dielectric function tensor model approach to render the optical response of monoclinic and triclinic symmetry materials with multiple uncoupled infrared farinfrared active modes. apply our $\beta$-Ga$_2$O$_3$ single crystal samples. Surfaces cut under different angles from bulk crystal, (010) ($\bar{2}$01), are investigated by generalized spectroscopic ellipsometry within spectral regions. determine frequency dependence 4 independent Cartesian elements matching large sets...
Anisotropic optical and transport properties of monolayer ReS2 fabricated by mechanical exfoliation are reported. Transient absorption measurements with different polarization configurations sample orientations reveal that the coefficient transient both anisotropic, maximal minimal values occurring when light is parallel perpendicular to Re atomic chains, respectively. The about a factor 2.5 values. By resolving spatiotemporal dynamics excitons, it found diffusion excitons moving along...
With a coupled spectroscopic ellipsometry-quartz crystal microbalance with dissipation (QCM-D) experimental setup, quantitative information can be obtained about the amount of buffer components (water molecules and ions) to poly(acrylic acid) (PAA) brush surface in swelling protein adsorption processes. PAA Guiselin brushes more than one anchoring point per single polymer chain were prepared. For swollen high was found brush-solution interface addition content inside layer. Upon bovine serum...
We report an experimental setup for wavelength-tunable frequency-domain ellipsometric measurements in the terahertz spectral range from 0.2 to 1.5 THz employing a desktop-based backward wave oscillator source. The instrument allows variable angles of incidence between 30° and 90° operates polarizer-sample-rotating analyzer scheme. source has tunable base frequency 107–177 GHz is augmented with set Schottky diode multipliers order extend THz. use odd-bounce image rotation system combination...
Generalized spectroscopic ellipsometry determines the principal monoclinic optical constants of thin films consisting slanted titanium nanocolumns deposited by glancing angle deposition under 85° incidence and tilted from surface normal 47°. Form birefringence measured for wavelengths 500 to 1000 nm renders Ti absorbing crystals with c-axis along nanocolumns, b-axis parallel film interface, 67.5° between a- c-axes. The columnar reveals anomalous dispersion, extreme birefringence, strong...
We report on optical, structural, and magnetic properties of two substantially different cobalt nanostructure thin films deposited at an oblique angle incidence 85° away from the substrate normal. Comparison is made between achiral columnar film grown without rotation a chiral nanocoil sculptured by glancing deposition with rotation. Generalized spectroscopic ellipsometry employed to determine geometrical structure anisotropic optical constants in spectral range 400 1000 nm. The are analyzed...
Generalized spectroscopic ellipsometry is used to determine the form-induced birefringence and monoclinic optical constants of chromium columnar thin films. The slanted nanocolumns were deposited by glancing angle deposition under 85° incidence are tilted from surface normal. Dichroism measured for wavelengths 400to1000 nm renders Cr absorbing crystals with c axis along axis, b parallel film interface, 74.8° between a axes. reveals anomalous dispersion, extreme birefringence, strong...
We report on the development of first integrated mid-infrared, far-infrared, and terahertz optical Hall effect instrument, covering an ultra wide spectral range from 3 cm−1 to 7000 (0.1–210 THz or 0.4–870 meV). The instrument comprises four sub-systems, where magneto-cryostat-transfer sub-system enables usage magneto-cryostat with mid-infrared ellipsometer sub-system, far-infrared/terahertz sub-system. Both sub-systems can be used as variable angle-of-incidence spectroscopic ellipsometers in...
Direct laser writing via two photon polymerization has enabled previously unavailable degrees of freedom in the additive fabrication micro-to-meso scale structures. The structures produced by these techniques are ideally suited to create optical devices which operate from THz regime near infrared spectrum into visible spectral range. Here we report on dielectric response monomers IP-dip and IP-L after frequently employed commercial lithography tools nanoscribe over range 250 cm−1 6000 cm−1....
The optical Hall effect is a physical phenomenon that describes the occurrence of magnetic-field-induced dielectric displacement at wavelengths, transverse and longitudinal to incident electric field, analogous static electrical effect. certain cases observations can be explained by extensions classic Drude model for transport electrons in metals. most useful characterization properties semiconductors. Among many advantages, while dispenses with need contacts, material such as effective mass...
We report for the first time on application of generalized ellipsometry at far-infrared wavelengths (wave numbers from 150 cm(-1) to 600 cm(-1)) measurement anisotropic dielectric response doped polar semiconductors in layered structures within an external magnetic field. Upon determination normalized Mueller matrix elements and subsequent derivation complex Jones reflection r n-type GaAs substrate covered by a highly resistive layer, spectral dependence room-temperature magneto-optic...
The temperature-dependence of free-charge carrier mobility, sheet density, and effective mass a two-dimensional electron gas in AlGaN/GaN heterostructure deposited on SiC substrate is determined using the THz optical Hall effect spectral range from 0.22 to 0.32 for temperatures 1.5 300 K. Hall-effect measurements are combined with room temperature mid-infrared spectroscopic ellipsometry determine layer thickness, phonon mode, parameters constituents. An increase (0.22±0.01)m0 at K...
We report on the first setup and experimental verification of terahertz frequency domain magneto-optic generalized ellipsometry using a combination highly brilliant synchrotron conventional blackbody radiation sources. The polarizer-sample-rotating-analyzer principle is employed to measure three normalized Stokes vector elements excluding depolarization information, upper left 3×3 block 4×4 Mueller matrix accordingly for wave numbers from 30to650cm−1 (0.9–20THz). discuss setup, measurement,...
We report on the evolution of polaron and phonon mode properties in amorphous tungsten oxide thin films measured by spectroscopic ellipsometry infrared to ultraviolet spectral regions as a function intercalated proton density. A parametric physical model dielectric is presented, which excellently describes data over large charge-density range. Upon increased amounts charge we observe strong increase absorption visible range, decrease W--O bond polarity, an $\text{W}=\text{O}$ polarity. Our...
We report on temperature, time, and voltage dependent resistive hysteresis measurements of BaTiO3-ZnO heterostructures grown (001) Si substrates by pulsed laser deposition. observe a diodelike behavior cycling-voltage formation under forward bias. explain these effects with depletion layer between the ZnO BaTiO3 layers, an additional barrier due to spontaneous polarization ferroelectric nature BaTiO3. The disappearance above ferroelectric-paraelectric phase transition temperature conformed...
Analysis techniques are needed to determine the quantity and structure of materials composing an organic layer that is below ultra-thin film limit in a liquid environment. Neither optical nor acoustical can independently distinguish between thickness porosity films due parameter correlation. A combined approach yields sufficient information both porosity. We describe application combinatorial measure single or multiple layers when total small compared wavelength probing light. The...
Spectroscopic ellipsometry in the mid-infrared and far-infrared spectral range generalized are used to investigate anisotropic dielectric response of rutile TiO2. The ordinary extraordinary function tensor components all infrared active phonon mode parameters single crystalline TiO2 determined with high accuracy for wavelengths from 3 μm 83 μm. data were acquired samples (001), (100), (111) surfaces cut bulk crystals. A factorized model is employed order determine frequencies damping...
We report noncontact, optical determination of free-charge carrier mobility, sheet density, and resistivity parameters in epitaxial graphene at room temperature using terahertz midinfrared ellipsometry optical-Hall effect measurements. The layers are grown on Si- C-terminated semi-insulating 6H silicon carbide polar surfaces. Data analysis classical Drude functions multilayer modeling render the existence a p-type channel with different densities effective mass for two optically obtained...
The free electron behavior in InN is studied on the basis of decoupled bulk and surface accumulation densities films measured by contactless optical Hall effect. It shown that variation density with film thickness does not follow models electrons generated dislocation-associated nitrogen vacancies. This finding, further supported transmission microscopy results, indicates existence a different thickness-dependent doping mechanism. Furthermore, we observe noticeable dependence density, which...
We present a dielectric continuum model approach for studying the electrical polarization properties of interface coupled ${\text{BaTiO}}_{3}$, ${\text{BaTiO}}_{3}\text{-ZnO}$, and ${\text{ZnO-BaTiO}}_{3}\text{-ZnO}$ thin-film structures consisting several hundred nanometer thick layers. Our augments effects electric field driven switchable depletion layer formation with spontaneous coupling. Wurtzite-structure (piezoelectric) $n$-type ZnO perovskite-structure (ferroelectric) highly...
The anisotropic optical dielectric functions of a metal (cobalt) slanted columnar thin film deposited by electron-beam glancing angle deposition are reported for the terahertz (THz) frequency domain using generalized spectroscopic ellipsometry. We employ simple effective medium function homogenization approach to describe observed response. describes isolated, electrically conductive columns which render biaxial (orthorhombic). Our findings suggest controlled variability polarizability and...