Spectroscopic Investigation of van der Waals Contacts between Semiconducting-TMD Monolayers and Semimetals

ORAL

Abstract

Before two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDs) can replace silicon-based electronic devices, the high contact resistance between the 2D semiconductors and their metallic contacts must be overcome. Although the Schottky–Mott rule (SMR) provides a simple model for metal–semiconductor contacts, it rarely holds experimentally, with Fermi-level pinning (FLP) effects dominating metal–semiconductor contacts through defect- and metal-induced gap states. The use of van der Waals interfaces composed of 2D semiconductors and semimetal contacts has been proposed to suppress FLP and restore SMR behavior. To test this conjecture, we fabricate pristine TMD/semimetal heterostructures across three monolayer TMDs (MoS2, WS2, WSe2) and two semimetals (Bi and graphite), then directly probe their interfacial electronic structures with scanning tunneling microscopy/spectroscopy, angle-resolved photoelectron spectroscopy, and field-emission resonance spectroscopy. We find that the SMR is recovered in TMD/Bi junctions, despite strong interlayer hybridization, while collapsing completely in weakly coupled TMD/graphite interfaces. With the aid of first-principles calculations, the underlying mechanism for this apparent contradiction will be discussed.

*This work was supported by the National Science Foundation (NSF) through the Center for Dynamics and Control of Materials: an NSF Materials Research Science and Engineering Center under cooperative agreement nos. DMR-1720595, DMR-23088157, the NSF grant no. DMR-2219610, the Welch Foundation F-2164, and the Taiwan Semiconductor Manufacturing Company, grant no. 202012170022, and the NSF graduate research fellowship program. Additionally, supported by the National Science and Technology Council (NSTC 113-2119-M-A49 -006 -MBK) and Academia Sinica (AS-GC-110-02).

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Publication: "Visualizing electronic structures across 2D semiconductor-semimetal interfaces - on the nature of Schottky contact," submitted to Nature Nanotechnology (2025).

Presenters

  • Lisa R Frammolino

    • The University of Texas at Austin

Authors

  • Lisa R Frammolino

    • The University of Texas at Austin

  • Fu-Xiang Chen

    • University of Texas at Austin
    • The University of Texas at Austin

  • Giovanny Espitia

    • The University of Texas at Austin
    • University of Texas at Austin

  • Fan Zhang

    • University of Texas at Austin

  • Yiyuan Luo

    • University of Texas at Austin

  • Yanxing Li

    • Princeton University
    • University of Texas at Austin

  • Hyunsue Kim

    • University of Texas at Austin

  • Andrew Murphy

    • University of Texas at Austin

  • Kaile Wang

    • University of Texas at Austin

  • Keji Lai

    • University of Texas at Austin

  • Zih-Siang Jian

    • National Yang Ming Chiao Tung University

  • Jian-Chen Tsai

    • National Yang Ming Chiao Tung University

  • I-Hsuan Chu

    • National Yang Ming Chia Tung University

  • Ming-Yang Li

    • Taiwan Semiconductor Manufacturing Company (TSMC)

  • Iuliana P. Radu

    • Taiwan Semiconductor Manufacturing Company (TSMC)

  • Wen-Hao Chang

    • Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
    • Academia Sinica
    • National Yang Ming Chiao Tung University, Academia Sinica
    • Department of Electrophysics, National Yang Ming Chiao Tung University

  • Mit Naik

    • University of Texas, Austin
    • University of Texas at Austin
    • The University of Texas at Austin

  • Chih-Kang Shih

    • University of Texas at Austin