Open Access. Powered by Scholars. Published by Universities.®
- Discipline
- Keyword
-
- Graphene (2)
- Solution processing (2)
- Bose-Hubbard Model (1)
- Calogero-Sutherland model (1)
- Charge Density (1)
-
- Coherent twin boundary (1)
- Contact resistance (1)
- Crystalline Films (1)
- Dirac Merger (1)
- Dislocations (1)
- Enhanced coupling (1)
- Exactly solvable (1)
- Excitons (1)
- Graphics Processing Units (1)
- Hubbard Model (1)
- Incoherent twin boundary (1)
- Magnetism (1)
- Metal semiconductor interface (1)
- Molecular dynamics (1)
- One-dimensional models (1)
- Optics (1)
- Organic (1)
- Organic Electronics (1)
- Organic Molecules (1)
- Organic Semiconductors (1)
- Organic thin film Crystallization (1)
- PIMC (1)
- Path Integral Monte Carlo (1)
- Path integral Monte Carlo (1)
- Photoconductivity (1)
Articles 1 - 8 of 8
Full-Text Articles in Condensed Matter Physics
Transient Effects In Solution-Processed Organic Thin Films, Jing Wan
Transient Effects In Solution-Processed Organic Thin Films, Jing Wan
Graduate College Dissertations and Theses
Due to the weak van der Waals forces between organic semiconductor molecules, the molecular packing depends sensitively on the processing methods and conditions. Thus, understanding the crystallization mechanisms during solution deposition are essential for fundamental studies and reproducible fabrication of electronic devices.The performance of Organic field effect transistors (OFETs) also depends heavily on extrinsic factors such as contact resistance and interfacial defects, which can produce a different kind of transient effect at the metal-semiconductor contact. We have observed structural transient effects during the crystallization process of two small molecule organic semiconductors made from solution. We report in situ X-ray scattering …
Two-Dimensional Bose–Hubbard Model For Helium On Graphene, Jiangyong Yu
Two-Dimensional Bose–Hubbard Model For Helium On Graphene, Jiangyong Yu
Graduate College Dissertations and Theses
An exciting development in the field of correlated systems is the possibilityof realizing two-dimensional (2D) phases of quantum matter. For a systems of bosons, an example of strong correlations manifesting themselves in a 2D environment is provided by helium adsorbed on graphene. We construct the effective Bose-Hubbard model for this system which involves hard-core bosons (U ≈ ∞) and repulsive nearest-neighbor (V > 0) interactions. In this work, we focus on the calculations of single particle properties of the model such as the hopping parameter t. This is accomplished via Wannier Theory and Band structure calculations, which proves to be reliable …
Accelerating Quantum Monte Carlo Via Graphics Processing Units, Benjamin Evert Himberg
Accelerating Quantum Monte Carlo Via Graphics Processing Units, Benjamin Evert Himberg
Graduate College Dissertations and Theses
An exact quantum Monte Carlo algorithm for interacting particles in the spatial continuum is extended to exploit the massive parallelism offered by graphics processing units. Its efficacy is tested on the Calogero-Sutherland model describing a system of bosons interacting in one spatial dimension via an inverse square law. Due to the long range nature of the interactions, this model has proved difficult to simulate via conventional path integral Monte Carlo methods running on conventional processors. Using Graphics Processing Units, optimal speedup factors of up to 640 times are obtained for N = 126 particles. The known results for the ground …
Excitonic States In Crystalline Organic Semiconductors: A Condensed Matter Approach, Lane Wright Manning
Excitonic States In Crystalline Organic Semiconductors: A Condensed Matter Approach, Lane Wright Manning
Graduate College Dissertations and Theses
In this work, a new condensed matter approach to the study of excitons based on crystalline thin films of the organic molecule phthalocyanine is introduced. The premise is inspired by a wealth of studies in inorganic semiconductor ternary alloys (such as AlGaN, InGaN, SiGe) where tuning compositional disorder can result in exciton localization by alloy potential fluctuations. Comprehensive absorption, luminescence, linear dichroism and electron radiative lifetime studies were performed on both pure and alloy samples of metal-free octabutoxy-phthalocyanine and transition metal octabutoxy-phthalocyanines, where the metal is Mn, Co, Ni, and Cu. Varying the ratios of the metal to metal-free phthalocyanines …
Polarization Charge Density In Strained Graphene, Noah Wilson
Polarization Charge Density In Strained Graphene, Noah Wilson
Graduate College Dissertations and Theses
Graphene, the world's first truly two-dimensional material, is unique for having an electronic structure described by an effective Lorentz invariant theory. One important consequence is that the ratio or Coulomb energy to kinetic energy is a constant, depending only on conditions within the lattice rather than on the average charge density as in a typical Galilean invariant material. Given this unusual property, a natural question would be how do phenomena, such as screening of a Coulomb impurity, happen in graphene? Moreover, how does the addition of uniaxial strain enhance or diminish this behavior? Here I discuss our work to calculate …
Exchange Mechanisms In Macroscopic Ordered Organic Magnetic Semiconductors, Naveen Rawat
Exchange Mechanisms In Macroscopic Ordered Organic Magnetic Semiconductors, Naveen Rawat
Graduate College Dissertations and Theses
Small molecule organic semiconductors such as phthalocyanines and their derivatives represent a very interesting alternative to inorganic semiconductor materials for the development of flexible electronic devices such as organic thin field effect transistors, organic Light Emitting Diodes and photo-voltaic cells. Phthalocyanine molecules can easily accommodate a variety of metal atoms as well in the central core of the molecule, resulting in wide range of magnetic properties. Exploration of optical properties of organic crystalline semiconductors thin films is challenging due to sub-micron grain sizes and the presence of numerous structural defects, disorder and grain boundaries. However, this can be overcome by …
The Interaction Mechanisms Of A Screw Dislocation With A Defective Coherent Twin Boundary In Copper, Qiongjiali Fang
The Interaction Mechanisms Of A Screw Dislocation With A Defective Coherent Twin Boundary In Copper, Qiongjiali Fang
Graduate College Dissertations and Theses
Σ3{111} coherent twin boundary (CTB) in face-centered-cubic (FCC) metals and alloys have been regarded as an efficient way to simultaneously increase strength and ductility at the nanoscale. Extensive study of dislocation-CTB interaction has been carried out by a combination of computer simulations, experiments and continuum theory. Most of them, however, are based on the perfect CTB assumption. A recent study [Wang YM, Sansoz F, LaGrange T, et al. Defective twin boundaries in nanotwinned metals. Nat Mater. 2013;12(8):697-702.] has revealed the existence of intrinsic kink-like defects in CTBs of nanotwinned copper through nanodiffraction mapping technique, and has confirmed the effect of …
Path Integral Quantum Monte Carlo Study Of Coupling And Proximity Effects In Superfluid Helium-4, Max Graves
Path Integral Quantum Monte Carlo Study Of Coupling And Proximity Effects In Superfluid Helium-4, Max Graves
Graduate College Dissertations and Theses
When bulk helium-4 is cooled below T = 2.18 K, it undergoes a phase transition to a superfluid, characterized by a complex wave function with a macroscopic phase and exhibits inviscid, quantized flow. The macroscopic phase coherence can be probed in a container filled with helium-4, by reducing one or more of its dimensions until they are smaller than the coherence length, the spatial distance over which order propagates. As this dimensional reduction occurs, enhanced thermal and quantum fluctuations push the transition to the superfluid state to lower temperatures. However, this trend can be countered via the proximity effect, where …