61 research outputs found
Native Point Defects in yttria as a High-Dielectric-Constant Gate Oxide Material: A First-Principles Study
Yttria (Y₂O₃) has become a
promising gate oxide material to replace silicon dioxide in metal-oxide-semiconductor (MOS) devices. The characterization of native point defect in Y₂O₃ is essential to understand the behavior of the material. We used the first-principles pseudopotential method to study the electronic structure, defect structure and formation energy of native point defects in Y₂O₃. Vacancies, interstitials and antisites in their relevant charge states are considered. The dominant defect types are identified under different chemical potentials and different Fermi levels. Oxygen vacancies are the dominant defect types under high yttrium chemical potential condition. Lower yttrium chemical potential leads to oxygen interstitials and ultimately yttrium vacancies when Y₂O₃ is used as a high dielectric constant gate oxide material in MOS devices.Singapore-MIT Alliance (SMA
Small Polarons in Transition Metal Oxides
The formation of polarons is a pervasive phenomenon in transition metal oxide
compounds, with a strong impact on the physical properties and functionalities
of the hosting materials. In its original formulation the polaron problem
considers a single charge carrier in a polar crystal interacting with its
surrounding lattice. Depending on the spatial extension of the polaron
quasiparticle, originating from the coupling between the excess charge and the
phonon field, one speaks of small or large polarons. This chapter discusses the
modeling of small polarons in real materials, with a particular focus on the
archetypal polaron material TiO2. After an introductory part, surveying the
fundamental theoretical and experimental aspects of the physics of polarons,
the chapter examines how to model small polarons using first principles schemes
in order to predict, understand and interpret a variety of polaron properties
in bulk phases and surfaces. Following the spirit of this handbook, different
types of computational procedures and prescriptions are presented with specific
instructions on the setup required to model polaron effects.Comment: 36 pages, 12 figure
A First-Principles Approach to Studying the Thermal Stability of Oxide Cathode Materials
Investigation of the Mixing Behavior and the Generation of Contact-Area in a Continuous Twin-Shaft Kneader
Investigation of the Mixing and Devolatilization Behavior in a Continuous Twin-Shaft Kneader
The technical synthesis and processing of polymer materials is the basis
for major branches of the chemical industry. Well introduced for high-viscosity
processes are screw extruders. However, in case of large residence times a large
volume kneader is more appropriate, but the latter still requires further understanding
for intensification purposes. To achieve this, silicone oil of high viscosity is
used as kneading material. First, the axial mixing behavior is characterized by
studying the residence time distribution. The response functions show that the
classical dispersion model leads to an appropriate description of the experimental
data. By means of a fast chemical reaction of second order the radial mixing behavior
including transport on the molecular scale is studied. The amount of detected
product is a measure for the contact-area produced by kneading and therefore for the
mixing efficiency. Furthermore, the mass transfer from the silicone oil phase to the
gas phase is investigated in two cases. Firstly, the transfer component is dissolved in
the liquid phase and, secondly, it is dispersed in it. Both industry relevant cases are
experimentally and theoretically investigated. The kneader enables high surface
renewal and larger concentration gradients for the efficient mass transfer
Native point defects in yttria and relevance to its use as a high-dielectric-constant gate oxide material: First-principles study
10.1103/PhysRevB.73.104101Physical Review B - Condensed Matter and Materials Physics7310-PRBM
First-principles study of native point defects in hafnia and zirconia
10.1103/PhysRevB.75.104112Physical Review B - Condensed Matter and Materials Physics7510-PRBM
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