PhD Proposal by Neha Kondekar

Event Details
  • Date/Time:
    • Tuesday April 24, 2018
      3:00 pm - 5:00 pm
  • Location: MRDC 3515
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    N/A
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Summaries

Summary Sentence: "Investigation of transformations in transition metal dichalcogenides during synthesis and operation of devices"

Full Summary: No summary paragraph submitted.

THE SCHOOL OF MATERIALS SCIENCE AND ENGINEERING

 

GEORGIA INSTITUTE OF TECHNOLOGY

 

Under the provisions of the regulations for the degree

DOCTOR OF PHILOSOPHY

on Tuesday, April 24, 2018

3:00 PM
in MRDC 3515

 

will be held the

 

DISSERTATION PROPOSAL DEFENSE

for

 

Neha Kondekar

 

"Investigation of transformations in transition metal dichalcogenides during synthesis and operation of devices"

 

Committee Members:

 

Prof. Matt McDowell, Advisor, MSE

Prof. Eric Vogel, MSE

Prof. Faisal Alamgir, MSE

Prof. Mark Losego, MSE

Prof. Satish Kumar, ME

 

Abstract:

 

Transition metal dichalcogenides (TMDCs) are promising candidates for electronics and energy storage devices. Materials such as MoS2 have been used for next-generation transistors, photosensors, electrocatalysts, and electrodes for Li-ion batteries. The highly anisotropic crystal structure of TMDCs features chemically active edge sites and relatively inert basal planes, which are bonded by weak Van der Waals forces. Careful control of the crystallographic orientation, composition, and layer thickness of TMDCs is critical to yield different electronic, chemical and optical properties. While obtaining uniform TMDC growth over large areas is necessary for commercialization of electronic devices, maximizing the fraction of edge sites exposed to the surface is thought to be required for enhancing catalytic activity. Thus, understanding the parameters that control structural properties of TMDC crystals is necessary for future applications.

 

Beyond controlling structural and electronic properties during synthesis of TMDCs, it is also critical to understand how structural and chemical properties of TMDC interfaces impact behavior in applications. For instance, interfacing TMDC layers with different metals and semiconductors is necessary for virtually all applications. Au and Pd are commonly used as metallic contacts in MoS2 transistors, which in turn are fabricated on Si or Ge wafers. In hydrodesulfurization catalyst materials used to extract sulfur from petroleum feedstock, Ni species are dispersed on the surface of MoS2 crystals. Ni-promoted MoS2 also serves as a cheap alternative to Pt for catalyzing the hydrogen evolution reaction (HER) during water splitting. The properties of TMDC heterointerfaces and the evolution of these interfaces under device operating conditions require dedicated further study to enable optimal performance.

 

The primary research objective of this proposed work is to understand and control the structural and chemical transformations within MoS2 and at its heterointerfaces both during synthesis and during operation of electronic/energy devices. Several in-situ and ex-situ characterization techniques will be used to investigate structural/chemical transformations. Preliminary results using in-situ X-ray photoelectron spectroscopy (XPS) show that the chemical transformations at MoS2/metal interfaces are dictated not only by the chemical reactivity of the interfaced material but also by the crystallographic orientation of MoS2 layers. This is attributed to different chemical and electronic properties of edge sites compared to basal planes in MoS2. These results suggest that careful control over the structure of interfaces is necessary for optimal charge transport in MoS2-based transistors and other electronic devices. Building on this understanding of interfacial chemistry, the proposed future work includes evaluating and improving the performance of TMDC electronic devices by controlling the structural and chemical configuration at the material-MoS2 interface. Furthermore, TMDC devices often experience elevated temperature during fabrication/processing, and the extent of interfacial transformations will be studied as a function of temperature. Finally, the influence of metal additions on the evolution of MoS2 crystals during synthesis will be investigated with in-situ methods. This proposed research is important because it will identify factors that currently limit the performance of TMDC-based devices.

Additional Information

In Campus Calendar
No
Groups

Graduate Studies

Invited Audience
Public, Graduate students, Undergraduate students
Categories
Other/Miscellaneous
Keywords
Phd proposal
Status
  • Created By: Tatianna Richardson
  • Workflow Status: Published
  • Created On: Apr 6, 2018 - 12:06pm
  • Last Updated: Apr 6, 2018 - 12:06pm