Atomic-scale engineering of 2D materials via scanning tunneling microscopy: Bridging synthesis, characterization, and device integration for post-silicon electronics
Wang, Hanfei
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https://hdl.handle.net/2142/129767
Description
Title
Atomic-scale engineering of 2D materials via scanning tunneling microscopy: Bridging synthesis, characterization, and device integration for post-silicon electronics
Author(s)
Wang, Hanfei
Issue Date
2025-05-02
Director of Research (if dissertation) or Advisor (if thesis)
Lyding, Joseph W
Doctoral Committee Chair(s)
Lyding, Joseph W
Committee Member(s)
Rakheja, Shaloo
Zhu, Wenjuan
Sinitskii, Alexander
Department of Study
Electrical & Computer Eng
Discipline
Electrical & Computer Engr
Degree Granting Institution
University of Illinois Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Low-dimensional materials
post-silicon electronics
graphene nanoribbons
coronoids
transition metal dichalcogenides.
Language
eng
Abstract
The semiconductor industry faces fundamental limitations as silicon-based technologies approach their physical and economic thresholds. Two-dimensional (2D) materials, including graphene nanoribbons (GNRs), coronoids, and transition metal dichalcogenides (TMDs), offer transformative potential for next-generation electronics due to their atomically thin nature, and tunable electronic and optical properties. This dissertation investigates the synthesis, atomic-scale characterization, and device integration of these materials using scanning tunneling microscopy (STM) and spectroscopy (STS) techniques. Graphene nanoribbons are engineered via various liquid phase synthesis methods to attempt precise control over width and edge structure for desirable electronic properties. STM/STS studies reveal that defects are a major issue in standard liquid phase synthesis of GNRs, while integrated iterative strategies demonstrate potential for structural uniformity for scalable device integration. GNR stacks of ribbons with randomly alternating widths and nitrogen endcaps provide an alternative device structure based on 2D materials. Coronoids, cyclic nanographenes with various cavity sizes, are synthesized via programmable head-to-tail cyclization. STM imaging highlights their strain-dependent bandgap modulation and emergent phenomena such as locallized metallic edges and lateral p-n junctions. In a move towards mixed-dimensional systems, the charge density wave (CDW) was observed in the 2D materials 1T-TaS2 was observed and studied at room temperature. Central to this work is the use of STM not only as a characterization tool but as a bridge between atomic scale understanding of 2D materials and functional device engineering based on these materials. The findings provide a roadmap for leveraging STM supported insights to the optimization of material preparation, correlation between structural and electronic properties, and the potential of 2D materials in post-silicon electronics.
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