Plasmonic 3D Metalattices and Plasmonic 2D Topological Insulator Heterojunctions: A Correlated Monochromated Electron Energy Loss Study and Theoretical Calculations

Session

PST.4 - Spectroscopies in Electron, X-ray and Ion Microscopy

Authors

Parivash Moradifar (1), Dr. Lei Kang (1), Dr. Tiva Sharifi (3), Saiphaneendra Bachu (1), Dr. Yunzhi Liu (1), Andrew Glaid (1), Prof. John Badding (1), Prof. Pulickel Ajayan (2), Prof. Douglas Werner (1), Prof. Nasim Alem (1)

Affiliations

1. Pennsylvania State University
2. Rice University
3. Umea University

Keywords

EELS, Plasmonic, Surface Plasmon Resonances,  Metamaterials, Topological Insulators, Chalcogenides, 2D, Field Enhancement, Aberration Corrected  Electron Microscopy

Abstract text

Surface plasmons enable routing and manipulating of light on sub-diffraction limit length scales. Surface plasmons are commonly excited by coupling to an electromagnetic field leading to confined local field enhancements effect^{(2) (3)} that be used for  strengthening the sub-diffraction light-matter interaction and open a path for extremely novel applications including ultra-efficient nanostructured solar cells, high speed nano-devices with the ability to compute and transport data on the speed of light, nanoscale endoscopes and photothermal biomedical therapeutic applications for less invasive and highly localized ablation of cancerous cells ^(4) (5). 

 

Various conventional noble metals (gold and silver) based nanostructures such as nanoparticles ^(6), nanorods ^{(7) (8)}, hollow structures ⁽⁹⁾, have been extensively studied for their well-known plasmonic responses at visible range spectrum regime due to their long relaxation time. Different surface plasmon resonance and very localized electric field enhancement was observed in these structures. However, there are strong motivations in exploring new plasmonic structures that exhibit lower resistive losses at optical frequencies and more functionally diverse properties.  Novel plasmonic building blocks such as metamaterials and topological insulators are considered to be two promising paths for exploring new plasmonic materials with exotic physical properties and lower resistive losses at optical frequencies in compare to conventional noble metals based nanostructures. 

 

As a novel candidate from 3D metamaterial nanostructures, this study would focus on metalattice nanostructures (subgroup of metamaterials) synthesized using high pressure confined chemical vapor deposition (HPcCVD), as a subwavelength novel periodic and long-range interconnected plasmonic nanostructure providing a versatile and tunable platform as integrated plasmonic interconnects for large optical confinement and long propagation distance applications in centimeter dimensions ⁽¹⁰⁾. Metalattice nanostructures are comprised of SiO₂ close-packed template in which the voids (meta-atoms, the tetrahedral and octahedral voids in the template, link through meta-bond, the thin channels connecting the tetrahedral and octahedral voids) are infiltrated by Ag.  We would further explore the effect of confinement, interconnectivity and substrate on excitation and propagation of various surface plasmon modes.

 

From the group of V-VI chalcogenides, this study will focus on Bi₂Te₃/Sb₂Te₃ in-plane heterojunctions as low-band gap semiconductors and topological insulators providing gapless metallic surface states. Bi₂Te₃ and Sb₂Te₃ have a rhombohedral crystal structure with space group of R3¯m. The bulk structure consists of alternating hexagonal monatomic crystal planes of Bi and Te arranging in ABC order along c-axis. Alternating sequences of Te (1)-Bi-Te (2)-Bi-Te (1) form units of 5 charge-neutral quintuple layers (QLs) along the c-axis tightly bounded through covalent bonding.  While adjacent QLs are predominantly bounded by weak van der Waals interactions. The crystal is easily cleaved along an inter-QL planes due to weak bonding between neighboring QLs ^(11) (12).  We would further determine the effect of intrinsic and externally induced defects in these 2D nanostructures on manipulation and modulation of surface plasmon modes through a systematic investigation.

 

Monochromated electron energy loss spectroscopy (Mono-EELS) in conjunction with aberration corrected scanning transmission electron microscopy (STEM) and x-ray energy dispersive (XEDS) combined with advanced data analysis were used to identify and spatially resolve various surface plasmon excitation modes and possible structural tools for manipulating plasmonic responses in these very dynamic platforms of 3D and 2D novel plasmonic building blocks. This work will also combine CST calculations to further elaborate the experimental EELS measurements.

This work was funded by the Penn State MRSEC, Center for Nanoscale Science, under the award NSF DMR-1420620.

References

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