University of Illinois Urbana-Champaign

Synthesis of 1T-Tantalum (IV) Sulfide and observation of charge density wave using scanning tunneling microscopy

Rajarajan, Sundaravadivel

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RAJARAJAN-THESIS-2015.pdf

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https://hdl.handle.net/2142/78417

Description

Title
Synthesis of 1T-Tantalum (IV) Sulfide and observation of charge density wave using scanning tunneling microscopy
Author(s)
Rajarajan, Sundaravadivel
Issue Date
2015-04-20
Department of Study
Electrical & Computer Engineering
Discipline
Electrical & Computer Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
M.S.
Degree Level
Thesis
Date of Ingest
2015-07-22T22:17:04Z
Keyword(s)
  • Charge Density Wave
  • Transition Metal Dichalcogenides (TMDC)
  • 1T-Tantalum (IV) Sulfide (1T-TaS2)
  • Tantalum Disulfide
  • Scanning Tunneling Microscope
  • Ultra-High Vacuum
  • 2D Material
  • Chemical Vapor Transport
Abstract
Over the past decade, due to the increasing interest and urgency in finding an alternate material system for post-silicon logic and opto-electronic applications, staggering progress have been made in the study of low-dimensional materials. These low-dimensional materials not only help reduce transistor footprint and improve power and performance metrics, they also exhibit very peculiar electrical properties. A particular example is the existence of a charge density wave (CDW) in 1T-Tantalum (IV) Sulfide (1T-TaS2). A member of the transition metal dichalcogenide (TMDC) family, 1T-TaS2 exhibit a periodic modulation of electronic charge density. Unlike bulk semiconductor or metals, lattice distortion in this low-dimensional material creates non-uniform, wave-like electron densities. In this thesis, we have demonstrated two bulk material growth strategies for the synthesis of 1T-TaS2. We have successfully grown poly-crystalline 1T-TaS2 powder through a direct solid-solid reaction and single-crystals of 1T-TaS2 through Iodine-assisted chemical vapor transport (CVT). After a few growth setup revisions, the growth processes have given consistently high yields. Next, we performed an ultra-high vacuum scanning tunneling microscopy (UHV-STM) study of the grown poly-crystalline 1T-TaS2. The powder was deposited onto an atomically flat, H-passivated silicon substrate using dry contact transfer (DCT), an in-situ deposition technique developed by the Lyding group for clean, UHV-compatible transfer of nano-materials. We managed to directly observe room-temperature CDW on the deposited nano-flakes of 1T-TaS2. The periodicity of the CDW lat- tice correspond very closely to the expected sqrt(13) x sqrt(13) nearly commensurate room-temperature CDW phase.
Graduation Semester
2015-5
Type of Resource
text
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http://hdl.handle.net/2142/78417
Copyright and License Information
Copyright 2015 Sundaravadivel Rajarajan

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