(59a) Electron Energy Loss Spectroscopy for Optoelectronics and Thermal Dynamics at Nanocomposite Interfaces

Electron energy loss spectroscopy for optoelectronics
and thermal dynamics at nanocomposite interfaces. 

D. Keith Roper^a,b*_, Jeremy R. Dunklin^d, Gregory T. Forcherio^c,
Keith R. Berry^b, Carter Bodinger^b, Tyler Howard^e

^a
Microelectronics
and Photonics Graduate Program, University of Arkansas, Fayetteville, AR
72701        

^b Department of Chemical
Engineering, University of Arkansas, Fayetteville, AR 72701

^cArmy Research Laboratory, Adelphi, MD 20783

^dNational Renewable Energy
Laboratory, Golden, CO 80401

^eDepartment of
Physics and Engineering Physics, Southeast Missouri State University, Cape
Girardeau, Missouri 63701

     Optoelectronically
active nanocomposite interfaces with programmable thermal dynamics could
improve medical diagnostics, therapeutics and sustainable energy recovery. Nanoantenna
at ceramic and polymer interfaces have been shown to enhance evaporative and pervaporative
phase change. But challenges in simulating, fabricating and characterizing nanoantenna
at solid-fluid interfaces has constrained their implementation in functional devices
and systems.

    
This work introduced electron energy loss spectroscopy (EELS) coordinated with
coupled dipole approximation (CDA), finite element modeling (FEM),
microthermometry and scanning electron microscopy (SEM) to develop
structure-property relations for optoelectronic and optothermal effects of
nanoantenna (NA) in nanocomposites and at interfaces. NA were integrated with
transition metal dichalcogenides, polymer thin films and ceramic surfaces by three
methods (i) drop-casting, (ii) solvent dispersion and (iii) electroless plating.
Electron energy loss spectroscopy (EELS) was used to predict and characterize modes,
damping and electromagnetic near fields of NA at nanocomposite interfaces (Fig.
1). Assembled NA were simulated using CDA to compare optoelectronic damping
with Mie theory, Maxwell Garnett effective medium theory (EMT), and measured
spectra (Fig. 2). Optothermal dissipation simulated by FEM using SEM was
compared with microthermometry to distinguish contributions from excitation, radiation,
conduction and convection (Fig. 3). Integrating results from these simulation
tools and novel integrated characterization approach supported relating effects
of geometry and composition for both NA and nanocomposite on equilibrium as
well as dynamic optoelectronic and optothermal properties of nanocomposites
[3].

    
The structure-property relations obtained were validated over ultraviolet,
visible, and near-infrared wavelengths and over greater than 10-fold changes in
relative values of internal and external thermal time constants.  Polymer thin
films and ceramics exhibited consistent interfacial thermal dynamics in both
liquid and gas media. Enhanced optical extinction and enhanced interfacial
energy transport observed in super-wavelength scale nanocomposites with
concentrated NA inclusions was attributable to optical diffraction.  

    
 Overall, coordination of EELS, CDA, FEM,
and SEM with transmission UV-vis spectroscopy and microthermometry supported a comprehensive
approach to simulate, fabricate and characterize nanocomposites and interfaces
decorated with optoelectronically active nanoantenna. Structure-function relations that appear valid across
a broad spectrum of material properties and operating conditions could guide
design of nanoantenna-containing nanocomposites for implementation in a variety
of uses.

 [1] G.T. Forcherio et al., Adv. Opt. Mat. (2016) 4(8) 1288 [2] T.V. Howard et al., submitted. [3]
D.K. Roper et al., in preparation.