Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session AAA10: V: Growth and Characterization |
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Sponsoring Units: DCMP Room: Virtual Room 10 |
Wednesday, March 22, 2023 12:30PM - 12:42PM |
AAA10.00001: Investigating electronic structure of surfaces using Auger mediated positron sticking induced electron spectroscopy V. A. Chirayath, Alexander Fairchild, Bernardo Barbiellini, V Callewaert, S Mukherjee, Sima Lotfimarangloo, Jack Driscoll, Brooke C Wallace, Randall Gladen, Ali R Koymen, Alex H Weiss Recent investigations in our lab demonstrated the ability of the new technique Auger mediated positron sticking induced electron spectroscopy (AMPSIES) to probe the electronic structure of the topmost atomic layer. In Auger mediated positron sticking (AMPS), the energy released during the quantum sticking of positrons on the sample surface is coupled to a valence band electron, which may then have enough energy to escape from the sample. Since the Columbic interaction between the positron and the electron during AMPS is highly screened, the probe depth is limited to one angstrom making the technique highly surface selective. Results obtained from the application of the method on single layer graphene on polycrystalline copper and polycrystalline copper after removal of the graphene overlayer provided conclusive proof that the electrons emitted following AMPS originates exclusively from the topmost atomic layer. Our measurements also showed conclusively that the energy spectrum of electrons emitted following AMPS reflects the surface density of states that is weighted by the matrix element of the AMPS process. Here, we report the AMPS induced electron spectra from Au (metal), Si (semi-conductor) and graphite (semi-metal) to demonstrate the applicability of the technique to wider systems and discuss the implications of our findings to surface spectroscopy using positrons. |
Wednesday, March 22, 2023 12:42PM - 12:54PM |
AAA10.00002: Application of Doppler Broadened Annihilation-Gamma Spectroscopy to extract elemental composition of topmost-atomic layers of external and internal surfaces Sima Lotfimarangloo, Varghese Chirayath, Jack Driscoll, Brooke C Wallace, Randall Gladen, Alexander Fairchild, Philip A Sterne, Ali R Koymen, Alexander H Weiss S. Lotfimarangloo, V. A. Chirayath, J. Driscoll, B. Wallace, R.W. Gladen, A. J. Fairchild, P.A. Sterne, A. R. Koymen and A. H. Weiss |
Wednesday, March 22, 2023 12:54PM - 1:06PM |
AAA10.00003: Island nucleation and growth with attachment barriers Jacques G Amar, Oliver Smirnov Island nucleation and growth play an important role in thin-film growth. One quantity of particular interest is the exponent χ which describes the dependence of the island-density N ~ (D/F)−χ on the ratio of the monomer diffusion rate D to the deposition rate F. While scaling arguments lead to the standard prediction that χ = i/(i + 2), where i is the critical island-size, it has been predicted by Kandel that in the presence of strong barriers to the attachment of monomers to stable islands, a significantly larger value χ = 2i/(i + 3) may be observed. Here, we present the results of self-consistent rate-equation calculations for i = 1, 2, 3 and 6 and kinetic Monte Carlo simulations for i = 1 and 2 which we have carried out to test this prediction. For the case of barriers to both stable island growth and island nucleation our results for i = 1-3 indicate agreement with the Kandel prediction in the asymptotic limit of strong barriers and large D/F. However, in the absence of nucleation barriers, we find that for i > 1, the asymptotic value of χ is significantly lower – although still larger than the standard prediction. A scaling argument is presented which may explain these results. |
Wednesday, March 22, 2023 1:06PM - 1:18PM |
AAA10.00004: Measurement of Surface Stress in Aluminum Induced by Organic Monolayer Films Anirudh Udupa, Debapriya Pinaki Mohanty, James Mann, Ronald M Latanision, Srinivasan Chandrasekar Adsorbed films on metal surfaces can trigger large-scale phenomena such as embrittlement and changes in surface plasticity. More recently, we have observed local embrittlement at the surface in large-strain deformation of metals triggered by nanometer-scale films. Some of these phenomena at least appear to be related to changes in surface stress (not surface energy) induced by the films. We describe a macroscale technique for measuring surface stress produced by organic monolayer films. Monomolecular films were deposited onto a thin aluminum foil cantilever (substrate) by molecular self-assembly. The foil, with thickness of 0.254 mm and length of 80 mm, is immersed in an organic solvent for the self-assembly. As the molecule adsorbs onto one side of the substrate, the cantilever tip deflects due to a change in surface stress induced by the film. The surface stress is estimated from in situ measurements of the tip deflection. Besides demonstrating the measurement technique for surface stress, our results show that this stress is strongly dependent on the molecule chain length. The rate of cantilever deflection can also be used to characterize adsorption kinetics. Implications for environmentally-assisted cracking and material removal processes for metals are discussed. |
Wednesday, March 22, 2023 1:18PM - 1:30PM |
AAA10.00005: Modeling Surface Structures and Dynamics of Diamond Grown Through Chemical Vapor Deposition Elyssa B Roeder, Tanvi Nikhar, Xavier Lewis, Jose L Mendoza-Cortes
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Wednesday, March 22, 2023 1:30PM - 1:42PM |
AAA10.00006: Infrared Optical Response of PdCoO2 thin film Dongmin Seo, Eunjip Choi, soonjae moon, Gihyeon Ahn, Seongshik Oh, Gaurab Rimal, Seunghyun Khim Optical properties of delafossite PdCoO2 thin film on Al2O3 have been obtained by reflectance, transmittance and ellipsometry measurements in frequency range from 60 cm-1 to 32000 cm-1. The ab-plane Drude electron exhibits frequency-dependent effective mass and the scattering rate, which indicates coupling of the carrier with a boson mode locate at Ω = 760 cm-1. We show that, through additional polarization-dependent measurements on PdCoO2 single crystal, a longitudinal optical (LO) phonon of c-axis corresponds to the boson mode. The coupling of ab-electron with c-axis LO phonon provides a new insight on the electrodynamics of layered metal oxide system. |
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