| 1/20 |
PAMS Faculty |
First week of classes: Introduction for new graduate students |
| 1/27 |
Christian Stepien (PAMS)
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Analysis of Thorium Ions in Chloride Aqueous Solutions using Raman Spectroscopy |
| 2/10 |
Devon Romine (PAMS) |
Modeling Atomic Layer Deposition of Alumina as an Ultra-Thin Tunnel Barrier Using Reactive Molecular Dynamics |
2/16
Zoom
Lunch |
Bandon Decker (PhD student)
University of Missouri-Kansas City |
Stellar Mass Properties of Infrared-selected High-redshift Galaxy Clusters from MaDCoWS |
NOTE: This is a lunch (12:00 pm) seminar!
Abstract: Galaxy clusters are the largest gravitationally-bound objects in the universe. Studying how these extreme structures grow and evolve over cosmic time is therefore of great importance. Although clusters are relatively well-studied in the local universe, studies of galaxy clusters at high-redshifts are more sparse owing to the difficulty in identifying large numbers of clusters and in getting suitable follow-up data on them. This period above z = 1 is a crucial period in cluster evolution as they stop forming stars and transition into the settled behemoths they are today. The Massive and Distant Clusters of WISE Survey (MaDCoWS) uses infrared WISE data to find the most significant galaxy overdensities at z ~ 1. Follow-up Sunyaev-Zel'dovich (SZ) observations have provided ICM confirmation of more than twenty MaDCoWS clusters—including MOO J1142+1527, the most massive cluster detected by any method above z = 1.15—while follow-up Spitzer/IRAC observations have allowed us to reliably measure their stellar mass. I will be showing comparisons of the stellar mass fractions of these high-redshift, infrared-selected MaDCoWS clusters to SZ-selected clusters from the South Pole Telescope (SPT) survey at similar redshift and to previous studies at low-redshift. I will also discuss recent work studying the evolution of the cluster luminosity function (LF) as a function of redshift, and what this tells us about cluster and galaxy evolution in these extreme environments. |
| 2/17 |
Emily Justus (PAMS) |
Applications of a Combined Approach of Kinetic Monte Carlo Simulations and Machine Learning to Model Atomic Layer Deposition (ALD) of Metal Oxides |
| 3/3 |
Dr. Mahmud Reaz
Microchip Technology Inc. |
Reliability of Silicon Devices - Hot Electron Effects |
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Dr. Reaz is an alum of PAMS where he received an MSc in Materials Science
Abstract: The feature-size on the current state-of-the art silicon technology have become so small that electron transport and associated reliability can no longer be understood with traditional efforts such as drift-diffusion or hydrodynamic models. Simulation complexity (resource constraint) restraints one to dynamically account for electron-electron scattering, electron-phonon scattering, impurity scattering, impact ionization, etc., altogether using atomistic quantum simulation. In this talk -- the Monte Carlo technique will be discussed to self-consistently (semiclassically) solve the Boltzmann-Poisson transport equations with full electronic and phonon energy bands to simulate the non-equilibrium carrier transport in materials and devices. Simulations of hot-carrier energy loss to the lattice and cold carriers show that the impact ionization and phonon interactions at or below ~5 eV energy primarily contribute to the experimentally derived radiation-ionization energies (3.69 eV/electron-hole pair in Si and 2.62 eV/ehp in Ge) of the semiconducting materials. In addition to an energy loss equal to the band gap energy via impact ionization, acoustic-phonon emission, which has been omitted in prior work, contributes 30% of the remaining carrier-energy loss, while optical-phonon emission contributes the other 70%. Next, the energy distributions of electrons in gate-all-around (GAA) Si MOSFETs are analyzed, including additional considerations for elastic interactions, which become important at reduced dimensions and high-carrier densities. The simulated density and average energy of the hot electrons correlate well with experimentally observed device degradation. The results imply that the interaction of high-energy electrons with hydrogen-passivated phosphorus dopant complexes within the drain may provide an additional pathway for interface-trap formation in these devices. Simulated momentum transfer events in the Si NW MOSFETs channel show that the Coulomb processes (often ignored as a higher-order phenomenon) significantly reduce mobility at low-field conditions - a phenomenon that already redefined Moore’s scaling law as we know it.
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| 3/10 |
Dr. Corrinne Mills
University of Illinois-Chicago & Fermilab |
Baryogenesis, Higgs Bosons, and What's Next |
| Abstract: Nearly 10 years after its discovery, the Higgs boson remains the subject of intense study at the Large Hadron Collider (LHC) because of its unique properties and potential connection to physics beyond the Standard Model. As our measurements become more precise and more comprehensive measurements, the observed Higgs boson looks ever more like the one predicted by the Standard Model. This is both an experimental triumph and a conundrum. With all of the particles predicted by the SM discovered, there is no single, obvious next target for searches, but most of the questions that motivated the construction of the LHC remain. I will talk about how my research addresses one of the outstanding questions, baryogenesis, through searches for additional Higgs bosons. Looking to the future, I argue that we are entering an experiment-driven era, and will need the best possible multipurpose detectors for the high-luminosity LHC and future colliders. I will talk about one of the tools that will take us there, a silicon semiconductor particle tracker of unprecedented precision and resilience. |
| 3/17 |
Spring break
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No seminar |
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3/24
Zoom
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Dr. Guang Bian
University of Missouri-Columbia |
Cloning of Dirac Electrons in Graphene/SiC Heterostructure |
| Abstract: Tuning interaction between Dirac states in graphene has attracted great interest because it modifies the spectra of the two-dimensional electron system and, consequently, gives rise to novel condensed-matter phases such as superconductors, Mott insulators, Wigner crystals and quantum anomalous Hall insulators. For example, emergent superconductivity occurs in twisted bilayer graphene at magic angles due to the enhanced correlation between Dirac fermions in the two graphene layers. In this work, we report a new way to engineer the band structure of graphene, namely, cloning Dirac states by the perturbation of substrate potential. We grow the graphene epitaxially on 6H-SiC substrate. The SiC surface potential exerts an incommensurate perturbation to the graphene Dirac bands, resulting in the duplication of Dirac states at different locations in the momentum space. The clone of the Dirac states has been observed in our angle-resolved photoemission spectroscopy (ARPES) experiments. We perform theoretical modelling to illuminate this cloning mechanism and show the possibility of controllably modifying the electronic spectra of two-dimensional atomic crystals by varying the substrate parameters. |
| 3/29 |
Farhan Ishrak (PAMS) |
Investigations of Mn-Co-NiO Based Heterostructured Nanocrystals |
| Abstract: Development of highly efficient, nanoscale based magnetic devices is an important goal for our society. We are investigating the synthesis, along with the structural and magnetic properties, of Mn- and Co-incorporated NiO heterostructured nanoparticles (HNPs). The synthesis of the HNPs is accomplished by first producing NiO nanoparticles using a thermal decomposition method. Subsequently, Mn-Co overgrowth phases are grown on the NiO nanoparticles via hydrothermal nanophase epitaxy. The crystalline structure and gross morphology of the synthesized HNPs are analyzed using XRD and SEM techniques. The composite architecture adds multifunctionality to HNPs, leading to a wide variety of potential applications, including energy storage, magnetic devices, photonics, and biomedicine. I will discuss the synthesis and characterization (XRD and SEM) of Ni(1-x-y)MnxCoyO heterostructured nanocrystals that were produced using procedures outlined above. |
| Sharif Uddin (PAMS) |
A Study of Bimagnetic CoO/NiFe2O4 Heterostructured Nanoparticles |
| Abstract: Bimagnetic nanoparticles show promise for applications in energy efficient magnetic storage media and magnetic device applications. The magnetic properties, including the exchange bias, of nanostructured materials can be tuned by variation of the size, composition, and morphology of the core vs overlayer of the nanoparticles (NPs). The purpose of this study is to investigate the optimal synthesis routes, structure and magnetic properties of CoO/NiFe2O4 heterostructured nanoparticles (HNPs). The nanoparticles are formed by synthesis of an antiferromagnetic CoO core and deposition of a ferrimagnetic NiFe2O4 overlayer. The CoO core NPs are prepared using thermal decomposition of Co(OH)2 at 600 °C for 2 hours in pure argon atmosphere, whereas the HNPs are obtained using a thermal evaporation method. The structural and morphological characterization, performed using XRD and SEM techniques, will be discussed. |
3/31
Zoom |
Dr. Soumitra SenGupta
Indian Association for the Cultivation of Science |
Gravitational Wave: The Song of the Cosmos |
| Abstract: Discovery of gravitational wave after one hundred years of the proposal of General Theory of Relativity as geometrical description of gravity opens up a new window to gain informations about our universe. The spectacular discovery of this in LIGO experiments marks a new era of our communication system through gravitational wave spectroscopy. In a simple language , I will briefly discuss about the theoretical description of gravitational wave from General theory of Relativity and it's consequent experimental detection in LIGO. |
4/7
Zoom |
Dr. Xiaobo Chen
University of Missouri-Kansas City |
Chasing Clean Energy and Environment Dream with Nanoscience: Photocatalysis, Rechargeable Battery, Hydrogen Production & Others – A Brief Summary of Our Past Research |
| Abstract: In this presentation, Dr. Chen will introduce and overview his past research efforts in the context of chasing the clean energy and environment dream with nanoscience and the graduate program at UMKC. That includes nanomaterials developments, photocatalytic hydrogen generation, photocatalytic pollution removal, rechargeable lithium ion battery, fuel cells, hydrogen storage, photothermal vapor generation, electrical hydrogen production, self-cleaning superhydrophobic coating, novel microwave absorbing materials, etc. |
| 4/14 |
Spring holiday |
No seminar |
4/21
Zoom |
Ripon Saha (PhD student)
University of Missouri-Kansas City |
Identifying Large-scale Structures Using Dust-obscured Galaxies (DOGs) as Signposts 9-10 Billion Light-years Away |
| Abstract: Galaxy clusters are the most massive collapsed structures in the universe. During cluster formation, the largest aggregation of gas, galaxies, and dark matter passes through an intermediate phase called the protocluster. Over the past decades, many studies have identified distant clusters and protoclusters due to advanced observational strategies. However, the protocluster-to-cluster transformation is still unclear, mainly due to the lack of large samples of early-stage clusters and late-stage protoclusters. Our research has identified a large selection of nearly 300 galaxy cluster candidates at redshift 1.3 < z < 1.8 (9-10 billion light-years away) during the formation epoch of the galaxy clusters. The candidates are identified using a sample of Ultra-Luminous Infrared Galaxies called the Dust-Obscured Galaxies (DOGs) as signposts in the Spitzer Deep Wide-Field Survey (SDWFS) in Boötes. A two-point correlation function analysis demonstrates that the sample has a mass scale of the galaxy clusters. Using a more multi-wavelength SDWFS catalog, this study has also uncovered a supercluster structure at z = 1.75 (10 billion light-years away). This supercluster is a bound structure hosting dozens of clusters of galaxies, including the most massive galaxy cluster (IDCS J1426.5+3508) found to date at z > 1.5. Finally, we develop and implement a novel machine learning technique to determine the photometric redshift (photo-z) of the distant galaxies using a TensorFlow-based deep learning network. The results will ultimately be used by a cluster-search project called the Massive and Distant Clusters of WISE Survey-II (MaDCoWS-II). |
| 4/28 |
Dr. Tommy Sewell
University of Missouri-Columbia |
Predicting Multiscale Responses of Organic High Explosives Subjected to Thermo-Mechanical Extremes
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Abstract: To establish the proper set and setting, I will begin with a brief overview of an interdisciplinary AFOSR “MURI” project that I lead which is focused on the development of integrated experimental and theoretical multiscale methods for understanding and predicting the response of organic composite high explosives to mechanical shock wave excitation. I will then narrow the focus onto a handful of vignettes that address: aspects of the fundamental nanoscale material mechanics, transport, and chemistry that occur in shocked molecular crystals, as determined from classical molecular dynamics (MD) simulations; some even more fundamental formal developments in the theory of thermal transport in dielectrics; a physics-constrained, MD-trained neural network approach for obtaining Helmholtz free-energy functionals which capture the single-crystal hyperelastic response in a form suitable for use in finite-strain continuum solid-mechanics simulations; and head-to-head comparisons between large-scale MD and continuum-mechanics predictions of shock-induced pore-collapse in molecular crystals, focusing on the sensitivity of the continuum results both to the mesoscale material model form and to the amount of fundamental information from the nanoscale used in the parameterization. It is not my intent to present the preceding in mind-numbing detail. Rather, I merely seek to convey a sense for the kinds of new knowledge and understanding of the nanoscale physics that we are obtaining and the methods by which they are achieved; how this fundamental information is being upscaled to the continuum mesoscale; and perhaps a few opinions as regards implications of our findings for future mesoscale material modeling of shock waves in complex systems.
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| 5/5 |
Dr. Xiangbo (Henry) Meng
University of Arkansas |
Atomic & Molecular Layer Deposition (ALD/MLD) for Emerging Research Studies |
| Abstract: Atomic and molecular layer deposition (ALD & MLD) are two powerful vapor-phase thin-film techniques. In the past decade, they have been attracting more and more attention. ALD and MLD share a similar growth mechanism relying on self-limiting gas-solid surface reactions. They both are operated with repeatable cycles to proceed film growth. Ascribed to their unique mechanism, ALD and MLD were born with a series of unrivaled capabilities, such as extremely uniform and conformal coatings over any substrates of any shapes, low growth temperature (typically ≤ 200 oC and even down to room temperature), and accurate growth controllability at the atomic and molecular level. Due to their different adoptions of precursors, ALD is exclusively for growing inorganic materials while MLD is specially for organic compounds. Consequently, they and their combination potentially can develop any materials from inorganics to organics and inorganic-organic hybrids, which are in existence and not in existence. Therefore, they have been providing us with new solutions in many applications, ranging from semiconductors to catalysis, new energies, biomedical, and surface engineering. In this talk, Dr. Meng will give an introduction on the basic principles of ALD and MLD, their historic development, and emerging applications. |
| 5/12 |
Dr. Hiro Nakamura
University of Arkansas |
Angle-resolved Photoelectron Spectroscopy: 2D Materials and Heterostructures |
| Abstract: In this seminar I will introduce recent advances in capturing electronic states in materials by using Angle-Resolved Photoelectron Spectroscopy (ARPES). Starting from basic principles of photoelectron effects, I will describe how different light sources (He lamp, synchrotron radiation, and lasers) are used for ARPES and their respective advantages. Finally, our recent experiments on 2D materials (TMDCs and graphene) will be shown to shed light on charge/energy transfer processes between the interface of 2D materials. |
| 5/19 |
Finals week |
No seminar |
