Bulletin of the American Physical Society
2017 Annual Fall Meeting of the APS Ohio-Region Section
Volume 62, Number 18
Friday–Saturday, October 13–14, 2017; Miami University, Oxford, Ohio
Session F2: Photonics and Nanoscience/Condensed Matter |
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Chair: Khalid Eid, Miami University Room: Kreger Hall 221 |
Saturday, October 14, 2017 8:30AM - 8:45AM |
F2.00001: Enhanced photonic-plasmonic laser emission from Zinc-doped GaAs nanowires Fatemesadat Mohammadi, Mykhaylo Lysevych, Hoe Tan, Chennupati Jagadish, Martin Fraenzl, Hans Peter Wagner Excitation power and temperature dependent lasing from Zinc-doped GaAs nanowires on glass and on metal films was investigated. NWs with an average diameter of 250 nm and 8 nm Al$_{\mathrm{2}}$O$_{\mathrm{3}}$ as top coating, were laid on glass, showed photonic lasing of the TE10 mode when the excited pulsed laser intensity exceeded 53 $\mu $J/cm$^{\mathrm{2}}$. Similar NWs on a metal film showed enhanced lasing and reduced excitation threshold that is attributed to the contribution hybrid photonic/plasmonic lasing modes. We suggest that the stronger light field confinement in the vicinity of the metal as well as the energy transfer from the NW emission to surface plasmons in the metal film leads to enhanced gain and reduced laser threshold. Observed blue shift of the NW lasing emission as a function of excitation intensity up to 200 $\mu $J/cm$^{\mathrm{2}}$ is attributed to band filling. The subsequent red-shift at higher intensities is caused by band-gap renormalization. At higher temperature, we observe both a red-shift and weakening of the emission that is attributed to band gap shrinkage and increasing non-radiative losses. While NWs on metal show lasing up to room temperature NWs on glass stop emitting at \textasciitilde 200 K. The enhanced robustness of lasing from NWs on metal is again attributed to light confinement and coupling with metal plasmons. [Preview Abstract] |
Saturday, October 14, 2017 8:45AM - 9:00AM |
F2.00002: Atomic Scale Proximity Effect at a Molecular Superconductor-Metal Kyaw Zin Latt, Sajida Khan, Anh Ngo, Hao Chang, Abdou Hassanien, Larry Curtiss, Saw-Wai Hla How a superconductor interacts with metal at a superconductor-metal boundary is vital for fundamental understanding of important phenomena such as Andreev reflection, and proximity effect. Here we investigate how the cooper pairs from a charged transfer based molecular superconducting cluster interact with 2-D surface state electrons from Ag(111) surface at the atomic scale using tunneling microscopy/ spectroscopy, and atomic/molecular manipulation schemes at low temperatures in an UHV environment. The superconducting molecular clusters are composed of a few molecular chains formed by BETS(donors) and GaCl4(acceptor). In STM images, these molecular clusters appear as ordered parallel chains resembling the `rafts'. Using STM manipulation, small molecular clusters are repositioned on the surface at desired locations. From the tip height signals, the dynamics of molecular clusters during their movements across the surface has been unveiled. Repeated manipulation experiments reveal that the rafts move only along [211] surface directions with single atomic site hops. Tunneling spectroscopy measurements across metal superconductor boundary provides variation of electron structures highlighting how surface state electrons interact with the superconducting clusters. [Preview Abstract] |
Saturday, October 14, 2017 9:00AM - 9:15AM |
F2.00003: Optical interaction of metal-induced-gap-state electrons and photon-assisted-tunneling electrons at the metal-insulator interfaces Mallik Mohd Raihan Hussain, Zhengning Gao, Domenico de Ceglia, Maria Vincenti, Andrew Sarangan, Imad Agha, Joseph Haus, Parag Banerjee, Michael Scalora We experimentally determined the delocalized electron density at metal-induced-gap-states (MIGS) in Au/Al$_{\mathrm{2}}$O$_{\mathrm{3}}$ (i.e. metal-insulator or MI) interfaces by applying a sensitive second harmonic generation (SHG) technique. We also observed an enhancement limit in the third harmonic generation (THG) at Au/Al$_{\mathrm{2}}$O$_{\mathrm{3}}$/Au (i.e. metal-insulator-metal or MIM) interfaces due to photon-assisted-tunneling (PAT). The Al$_{\mathrm{2}}$O$_{\mathrm{3}}$ layer was deposited on planar Au samples using atomic layer deposition (ALD) technique to form Al$_{\mathrm{2}}$O$_{\mathrm{3}}$/Au interface. Later, Au nanoparticles of diameter 20nm were immobilized on Al$_{\mathrm{2}}$O$_{\mathrm{3}}$ layer to prepare Au/Al$_{\mathrm{2}}$O$_{\mathrm{3}}$/Au interface. Second and third harmonic signals were extracted in each step. Simulations were done using finite-element-method to compare with the experimental results. The experimental results match qualitatively to the prediction of quantum conductivity theory (QCT). [Preview Abstract] |
Saturday, October 14, 2017 9:15AM - 9:30AM |
F2.00004: Fabrication of periodically poled lithium niobate for conversion experiments Matthew Mircovich, Jay Mathews, Imad Agha Lithium niobate (LN) is a nonlinear crystalline material in which second order nonlinear processes can occur. By applying a strong electrical field, domain reversal (reversal of the optical axis) of the crystal can be achieved, allowing for enhancement in nonlinear optical interactions. In fact,~Periodically Poled Lithium Niobate (PPLN) has a high degree of effective nonlinearity due to the increased interaction length, made possible through phase-matching. Fabrication starts with a wafer of congruent lithium niobate that is diced into the appropriate size. The wafer is periodically patterned with photoresist, then placed inside a conductive electrolyte solution and held at a constant temperature. A high voltage is applied through the solution, contacting the wafer where the resist is absent. A 3-5 kV pulse is applied through the electrolyte, causing a domain reversal between the photoresist, leading to periodic poling. The fabricated PPLN will be used for frequency up conversion, down conversion, as well as basic building blocks for optical parametric oscillators. [Preview Abstract] |
Saturday, October 14, 2017 9:30AM - 9:45AM |
F2.00005: Electric Field Driven Void Percolation Around Spheres and Plates Nicholas McGuigan, Donald Priour In practice, fluid flow through technologically relevant materials is not through well defined channels but through voids around barrier particles. In spite of the structural disorder, percolation phenomena are seen where below a critical density of impenetrable particles macroscopic flow is possible, whereas above this density threshold bulk fluid transport is blocked. As representative examples we examine systems composed of randomly placed spheres and infinitely thin plates, for which in the latter case the plate orientations are also random. The former system serves as a validation of our approach which involves charged tracer particles driven through the matrix by a uniform electric field with collisions with barrier particles taken into account as specular reflections. In the case of a medium comprised of disordered plates with zero thickness, our calculation of the critical density of plates is the first calculation of the percolation threshold for this system. The unidirectional exploration of our electric field driven approach is an element which significantly enhances both the computational efficiency and system sizes accessible. [Preview Abstract] |
Saturday, October 14, 2017 9:45AM - 10:00AM |
F2.00006: Potential-Descending Principle and Statistical Theory of Heat Shouhong Wang, Tian Ma The aim of this talk are two-fold. First we postulate the potential-descending principle (PDP), and to show that PDP leads to 1) the 1st and 2nd laws of thermodynamics, and 2) three classical distributions: Maxwell-Boltzmann, Bose-Einstein and Fermi-Dirac. Hence PDP serves as the first principle for statistical physics. We also show that PDP is the first principle for irreversibility for all thermodynamic systems, and the thermodynamic potential, rather than entropy, is the correct physical quantity for irreversibility. Second, we present a new theory of heat. The main results include 1) energy level formula of temperature, 2) photon number entropy formula, 3) law of temperature, and 4) thermal energy formula. The photon number entropy formula is equivalent to the Boltzmann entropy formula. But the new formula possesses new physical meaning that the physical carrier of heat is the photons. [Preview Abstract] |
Saturday, October 14, 2017 10:00AM - 10:15AM |
F2.00007: The Influence of Different Treatments of Surface Chemistry on Titanium via X-Ray Photoemission Spectroscopy David Bernard, Hannah Senediak, Eruj Arif, Veronica Marcella, Lauren Debow, Patrick McWhorter, Holly Martin, Snjezana Balaz Various implant grade titanium analogs were treated with non-carcinogenic deposition agents (acetone, heptane, ethanol) and compared with a carcinogenic deposition agent toluene to determine the effect that each method has on the surface chemistry of the analog. For use in biological implants, a non-carcinogenic solution such as these would be required by the Food and Drug Administration (FDA). Our study focused on the surface chemistry between treatments as well as investigating different bonding characteristics of the various agents using X-Ray Photoemission Spectroscopy (XPS) in an Ultra High Vacuum (UHV). Each analog was passivated, submerged in ultra pure water, submerged in an APTES solution containing the deposition agent, submerged in glutaraldehyde, and a deposition of chitosan. Between each stage the analogs were analyzed via XPS examining oxygen, carbon, nitrogen, and silicon at high resolution to determine the subtle differences in bonding characteristics while titanium was examined to determine the completeness of adhesion of the chitosan to the titanium substrate. [Preview Abstract] |
Saturday, October 14, 2017 10:15AM - 10:30AM |
F2.00008: Investigations into sensitizing GaP photocathodes with CdSe quantum dots Desislava Dikova, Molly MacInnes, Sudarat Lee, Stephen Maldonado Quantum dots (QDs) have gained interest due to their interesting and highly tunable optoelectronic properties. In particular, CdSe QDs have widespread applications including biological fluorescence, LEDs, lasers, and solar cell sensitization. The purpose of this project is to photosensitize single crystal GaP photocathodes with CdSe QDs possessing a larger band gap than that of GaP. Sensitizing a solar cell surface is a relatively cheap way to increase the efficiency of the cell, by generating more power than unsensitized cells. Additionally, as a polycrystalline material, GaP is inherently more expensive than Si solar cells, so increasing GaP efficiency is a step towards implementing it as a commercial solar cell. In this work, CdSe QDs of varying sizes have been synthesized using a highly reproducible procedure. The quality of the QDs and their physisorption onto GaP have been monitored using fluorimetry, uv-vis absorption spectroscopy, x-ray photoelectron spectroscopy, and transmission electron microscopy. During the synthesis process, CdSe QDs are capped with long, insulating ligands; the ligand exchange is a crucial aspect of facilitating charge transfer between QDs and GaP. Ligand exchange methods are investigated in this work; however, photosensitization has not yet been observed. Further study will be conducted on depositing a usefully thick layer of QDs that doesn't insulate or protect the GaP surface, using different ligands or a ZnSe shell. [Preview Abstract] |
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