56 research outputs found
Modeling Temperature, Frequency, and Strain Effects on the Linear Electro-Optic Coefficients of Ferroelectric Oxides
An electro-optic modulator offers the function of modulating the propagation
of light in a material with electric field and enables seamless connection
between electronics-based computing and photonics-based communication. The
search for materials with large electro-optic coefficients and low optical loss
is critical to increase the efficiency and minimize the size of electro-optic
devices. We present a semi-empirical method to compute the electro-optic
coefficients of ferroelectric materials by combining first-principles
density-functional theory calculations with Landau-Devonshire phenomenological
modeling. We apply the method to study the electro-optic constants, also called
Pockels coefficients, of three paradigmatic ferroelectric oxides: BaTiO3,
LiNbO3, and LiTaO3. We present their temperature-, frequency- and
strain-dependent electro-optic tensors calculated using our method. The
predicted electro-optic constants agree with the experimental results, where
available, and provide benchmarks for experimental verification.Comment: 30 pages, 6 figures, 2 tables and 2 boxe
Crystal growth and structural analysis of perovskite chalcogenide BaZrS and Ruddlesden-Popper phase BaZrS
Perovskite chalcogenides are gaining substantial interest as an emerging
class of semiconductors for optoelectronic applications. High quality samples
are of vital importance to examine their inherent physical properties. We
report the successful crystal growth of the model system, BaZrS and its
Ruddlesden-Popper phase BaZrS by flux method. X-ray diffraction
analyses showed space group of with lattice constants of = 7.056(3)
\AA\/, = 9.962(4) \AA\/, = 6.996(3) \AA\/ for BaZrS and
with = 7.071(2) \AA\/, = 7.071(2) \AA\/, = 25.418(5) \AA\/ for
BaZrS. Rocking curves with full-width-at-half-maximum of
0.011 for BaZrS and 0.027 for BaZrS were
observed. Pole figure analysis, scanning transmission electron microscopy
images and electron diffraction patterns also establish high quality of grown
crystals. The octahedra tilting in the corner-sharing octahedra network are
analyzed by extracting the torsion angles.Comment: 4 Figures, 2 Table
A hybrid pulsed laser deposition approach to grow thin films of chalcogenides
Vapor-pressure mismatched materials such as transition metal chalcogenides
have emerged as electronic, photonic, and quantum materials with scientific and
technological importance. However, epitaxial growth of vapor-pressure
mismatched materials are challenging due to differences in the reactivity,
sticking coefficient, and surface adatom mobility of the mismatched species
constituting the material, especially sulfur containing compounds. Here, we
report a novel approach to grow chalcogenides - hybrid pulsed laser deposition
- wherein an organosulfur precursor is used as a sulfur source in conjunction
with pulsed laser deposition to regulate the stoichiometry of the deposited
films. Epitaxial or textured thin films of sulfides with variety of structure
and chemistry such as alkaline metal chalcogenides, main group chalcogenides,
transition metal chalcogenides and chalcogenide perovskites are demonstrated,
and structural characterization reveal improvement in thin film crystallinity,
and surface and interface roughness compared to the state-of-the-art. The
growth method can be broadened to other vapor-pressure mismatched chalcogenides
such as selenides and tellurides. Our work opens up opportunities for broader
epitaxial growth of chalcogenides, especially sulfide-based thin film
technological applications.Comment: 27 page
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