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"Correlating the Optical Property Evolution in Au-Ni Binary Thin Films: From Metastable Solid Solution to Phase Separated Alloy" & "O2 Plasma Processing of Thin Film Layered Semiconductors"

MATERIALS  SEMINAR
Department of Materials Science & Engineering
Tuesday April 2, 2019
2:15 – 3:15 ~ SERF 307
Please join us for refreshments at 2:10

"Correlating the Optical Property Evolution in Au-Ni Binary Thin Films: From Metastable Solid Solution to Phase Separated Alloy"

Speaker: Robyn Collette
Ph.D Candidate, Materials Science and Engineering
Advisor:  Philip Rack
University of Tennessee, Knoxville


Abstract:

In this study, the optical properties of Au1-xNix alloy thin films are investigated by employing a combinatorial sputtering approach. The dielectric function is measured using spectroscopic ellipsometry and is correlated to the composition, and phases present. As-deposited alloys form a metastable solid solution, however, annealed alloys exhibited phase separation into Au-rich and Ni-rich phases due to the large miscibility gap in the Au-Ni material system. The optical properties are then rationalized by modeling the dielectric function of the solid solution alloys with a Drude-Critical Point analytical model. Lastly, the efficacy of the model is demonstrated which shows that the dielectric function of the phase separated alloys can be approximated using a composition-weighted average of two solid solution dielectric functions.


Biography:

Robyn Collette is a third-year graduate student in the department of Materials Science and Engineering at UTK. She is a Chancellors Fellow through the UT College of Engineering. Before coming to Tennessee, Robyn graduated from Shippensburg University of Pennsylvania in 2016 with a BS in Physics. Her research focus is metallic alloys for plasmonic materials.
 

 

"O2 Plasma Processing of Thin Film Layered Semiconductors"

Speaker: Anna Hoffman 
Ph.D Candidate, Materials Science and Engineering
Advisor:  Philip Rack
University of Tennessee, Knoxville


Abstract:
Controlled oxygen plasma exposure of multilayer WSe2 can modulate the carrier type of WSe2 field effect transistors. XPS shows with increased exposure, the top WSe2 layer(s) oxidizes to amorphous WO(x-3) layer-by-layer with a high degree of controllability as both single or bi-layers can be transformed. A systematic study of Raman and photoluminescence signatures clearly demonstrate the processing times necessary to selectively oxidized the top 1 or 2 layers of exfoliated WSe2 flakes. WSe2 devices exposed in the channel regions experience an increase in p-type conduction and large layer-dependent n-type suppression. Devices exposed in the contact region prior to metalization show slight increases of both p-type and n-type conduction. Devices made on flakes, which were completely exposed show suppression of p-type conduction and layer dependent suppression of n-type conduction. Based on these results we were able to fabricate self-rectifying lateral p-n homojunctions with rectification ratios exceeding 300.


Biography:
Anna Hoffman is a 4th year Ph.D student in Dr. Philip Rack’s group. Her research interests include optoelectronic properties of 2D materials, nanofabrication, and thin film processing methods. She received her undergraduate degree in Materials Science and Engineering in 2015 at The Georgia Institute of Technology in Atlanta. She enjoys volunteering in the City of Knoxville Special Events department as a break from graduate work. 
 

Tuesday, April 2, 2019 at 2:10pm to 3:15pm

Science and Engineering Research Facility (SERF), 307
1414 Circle Dr, Knoxville, TN 37996

Event Type

Lectures & Presentations

Topic

Engineering

Audience

Current Students, Faculty & Staff

Tags

MSE Seminar

Department

Materials Science and Engineering

Hashtag

#Collette&HoffmanSeminar

Contact Name

Ashley Cole

Contact Email

acole14@utk.edu

Contact Phone

865-974-5336

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