Detection of plasmonic behavior in colloidal indium tin oxide films by impedance spectroscopy
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Research Letter
Detection of plasmonic behavior in colloidal indium tin oxide films by impedance spectroscopy Salil M. Joshi, Ning Xia, Yolande Berta, Yong Ding, and Rosario A. Gerhardt, School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA Kenneth C. Littrell, Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA Eric Woods and Mengkun Tian, The Institute for Electronics and Nanotechnology, Georgia Institute of Technology, Atlanta, GA 30332, USA Address all correspondence to Rosario A. Gerhardt at [email protected] (Received 17 January 2020; accepted 23 March 2020)
Abstract Impedance spectroscopy was conducted on colloidal ITO thin films that had been subjected to alternating oxygen and argon plasma treatments, followed by air annealing from 150 to 750 °C. An equivalent circuit consisting of an RC element nested within another RC element, featuring a negative resistance and a negative capacitance, fitted the data well. These results are interpreted as being due to surface plasmons that are a function of the presence of nanoporous ITO-rich regions surrounded by isolated ITO nanoparticles coated with an amorphous polymer that intertwines with the ITO-rich regions as a function of annealing treatment.
Background The bulk of electrical characterization done all over the world is based on DC-based measurements. However, the majority of the electrical phenomena in nature and in industry is dynamic and transient. DC characterization methods are insufficient to probe and understand them. The general approach to measuring electrical properties in the DC mode involves applying an electrical stimulus such as a potential difference or current to a sample and measuring the response, such as the current or the potential difference. These measurements are often done with the implicit assumption that a steady state has been reached; or after waiting for a sufficient time to let the system approach a steady state. Thus, such measurements either assume that properties of the electrode-material system are time-invariant,[1] or these measurements ignore the transient behavior that usually accompanies the application of the electrical stimulus. A multitude of fundamental microscopic processes take place when a system is electrically stimulated, the sum of which forms the electrical response.[1–3] These processes can include the transport of charge carriers (mobile electrons, holes, or ions) through conductors, transfer of charge carriers at interfaces, movement, and alignment of electrical dipoles, electrochemical reactions that involve the creation, recombination, or the change in the oxidation state of ionic species. The transport processes are further modified by defects and band structure details. Much more information about these processes can be obtained by characterization through impedance spectroscopy (IS). IS is the measurement of the complex impedance of a sample or of a system, by measuring the current response and the phase lag of a sy
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