Bulletin of the American Physical Society
Mid-Atlantic Section 2022 Meeting
Volume 67, Number 20
Friday–Sunday, December 2–4, 2022; University Park, PA, Pennsylvania State University
Session E04: Nanostructures |
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Chair: Burcu OZDEN, Pennsylvania State University Room: Pennsylvania State University Osmond 106 |
Saturday, December 3, 2022 2:00PM - 2:35PM |
E04.00001: Electronic and structural properties of rare-earth mono-pnictide (RE-V) nanoparticles in III-V matrices Invited Speaker: Ruiqi Hu Embedding semi-metallic rare-earth mono-pnictide (RE-V) nanoparticles into III-V semiconductors enables nanocomposites with a wide range of optical, electrical, and thermoelectric properties. The inclusion of nanostructured components in a III-V increases the area of interfaces contributing to decreased carrier lifetime, increased phonon scattering, and reduced thermal conductivity, also providing enhanced electrical conduction through electron filtering mechanisms. The common group-V sublattice offers an interesting matching across interfaces of the rock-salt semimetal RE-V (e.g. ErAs) to the zinc-blende semiconductor III-V (e.g. GaAs, AlAs) matrices with similar lattice parameters. First-principles calculations based on density functional theory (DFT) calculation with the modified Becke-Johnson meta-GGA (mBJ) functional are used to describe the electronic properties of ErAs nanoparticles embedded in GaAs and AlAs. We investigate the stability of different nanoparticle shapes and sizes, from cubic to spherical, deriving a direct correlation between the electron density and atomic density associated with excess metal atoms at the interface. We find that spherical nanoparticles lead to lower atomic density at the interface and low formation enthalpies; the shape, size, and structure of the nanoparticles show good agreement with images obtained from transmission electron microscopy. Comparison of atom-resolved density of states (DOS) for different size and shaped nanoparticles with the parent compound materials allows for alignment the Fermi level of the nanoparticle systems with band edges of the semiconductors, showing that the Fermi level is pinned in the band gap. Our results show that as the size of ErAs nanoparticles increases, the Fermi level moves from near the conduction band for very small particles to the middle of the gap. Our predictions serve to guide the design of nanocomposite materials with targeted properties. |
Saturday, December 3, 2022 2:35PM - 2:47PM |
E04.00002: Valley axion field and surface phonon modes in 3D time reversal invariant Dirac materials Abhinava Chatterjee, Chaoxing Liu Axion electrodynamics can emerge in 3D topological materials and plays an essential role in a variety of physical phenomena, including surface half quantum Hall effect, topological magneto-optical response, chiral/helical fermions along dislocations, magnon-polariton, etc. In this work, we consider a thin film of a 3D time reversal invariant Dirac semi metal Na3Bi and find that the effective action of the phonon degrees of freedom due to a strain-induced pseudo gauge field (valley dependent) takes the form of axion electrodynamics. The axion field mainly influences the surface phonon modes with no significant contribution in the bulk. In the presence of a surface thermal gradient, the axion field gives rise to additional non-vanishing angular momentum response coefficients. We calculate numerically the angular momentum response coefficients as a function of the axion field. |
Saturday, December 3, 2022 2:47PM - 2:59PM |
E04.00003: Absorption properties of Iron and Sulfur doped Graphene Carbon Quantum Dots Jorge A Cuadra Aparicio, J. C. Molina, N. Cisneros, F. Bonilla, R. Estrada, D. Pleitez, H. Ponce, C. Rudamas Graphene Carbon Quantum Dots (GCQDs) are carbon nanostructures that have great optoelectronic properties and low toxicity which makes them excellent candidates for relevant technologies. Most studies on GCQDs report high absorption in the UV range and weak or none in the VIS range. The latter limits the use of GCQDs for applications such as solar cells, which require strong absorption in this range. A solution to this problem is to dope the carbon nanostructure. Extensive research is being performed to find suitable doping atoms or molecules to extend the absorption range of GCQDs. In this work, we report the doping of CQDs by Iron (Fe) and Sulfur (S) atoms (S-Fe-GCQDs) by pyrolysis of citric acid. Their optical properties were studied experimentally, by absorption and Raman spectroscopy, and theoretically by DFT. The measured absorption spectra show absorption bands around the UV and green-yellow part of the VIS range. From the Density of States these observed bands in the VIS region could be associated with electronic transitions between the n-π* (S-C) and n-π* (Fe-C) states. Raman peaks associated with C=C-S and Fe-C-O vibrations support the successful doping of S and Fe atoms in the GCQD structures. |
Saturday, December 3, 2022 2:59PM - 3:11PM |
E04.00004: Systematic study of Bi-Sb Thin Films Grown by Molecular Beam Epitaxy via X-ray and Raman Spectroscopy Yu-Sheng Huang, Yongxi Ou, Nitin Samarth The material Bi x Sb 1−x is a promising candidate for spin-orbit torque (SOT) applications due to its potentially high figure of merit for spin-charge interconversion. This is due to the strong spin-orbit coupling and topological features in the electronic band structure in the appropriate composition range. We systematically grow a series of Bi x Sb 1−x thin films using molecular beam epitaxy and verify their composition using X-ray photoelectron spectroscopy and angle-resolved photoemission spectroscopy measurements. We then study their detailed structural characterization via x-ray diffraction, transmission electron microscopy, and reflection high energy electron diffraction. Finally, we use Raman spectroscopy to investigate the phonon modes in these thin films and compare the results with those from bulk-grown Bi x Sb 1−x crystals previously reported in the literature. |
Saturday, December 3, 2022 3:11PM - 3:23PM |
E04.00005: CdS quantum dot surface defect emission for white light emitting diodes. Oscar Armando A Jorge Deodanes, Juan C Menjívar Molina, Nelson F Méndez Cisneros, David A Rafael Pleitez, Jorge A Cuadra Aparicio, Hamilton A Ponce Elías, Carlos Rudamas The application of quantum dots (QDs) in white LEDs (WLEDs) have been rapidly growing as a promising option to replace current illumination sources. Commonly in these devices, the band edge emission of the QDs is used, trying to eliminate emission associated to QD surface defects. However, a relevant contribution of the surface defect emission to the photoluminescence (PL) quantum yield in these nanostructures has been reported. In fact, it has been pointed out that surface state emission could also be used in the fabrication of WLEDs and some effort have been done to tune, increase and control it. However, the PL properties are still not well understood. |
Saturday, December 3, 2022 3:23PM - 3:58PM |
E04.00006: Advancing Material Science With Thomas-Fermi Models Invited Speaker: Michele Pavanello Electronic structure methods are routinely used in materials science to predict properties of materials. A commonly broadcast message is that complex workflows, including high throughput simulations, lead to the design of novel materials with desired properties. Roadblocks given by the high computational complexity of off-the-shelf electronic structure solvers become insurmountable as the model systems considered become larger than a few nanometers. Unfortunately, this has negative repercussions to the impact and scope of modern computational material design. To attack the issue at hand, in recent years Thomas-Fermi models, also known as orbital-free DFT, have been revisited with great success for both equilibrium [2,3,5,7,8] and non-equilibrium [1,4,6] dynamics of materials. We present recent progress in the development of relevant software [8] and energy functionals [5,7] and potentials [1,4,6] for time-dependent electronic structure simulations and their application to materials interfaces and metal and semiconducting nanoparticle plasmon resonance predictions. |
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