Fabrication and characterization of MoTe2 field effect transistor

Zhang, Jingyi (2024) Fabrication and characterization of MoTe2 field effect transistor. PhD thesis, University of Glasgow.

Abstract

For nearly half a century, the scaling of silicon (Si) CMOS field-effect transistors (FETs) has driven advancements in microelectronics, as predicted by Moore’s Law. However, as device dimensions reach nanometre scales, the physical limitations of traditional materials have become evident. Two-dimensional (2D) materials, such as transition metal dichalcogenides (TMDCs), present a promising alternative for next-generation devices due to their unique properties, including flexibility and high carrier mobility. These materials are particularly well-suited for 'More than Moore' devices, which aim to enhance CMOS technology by introducing additional functionalities.

This dissertation investigates the fabrication and characterisation of MoTe2-based FETs. First, a novel chemical vapour deposition (CVD) method for the selective growth of 2H- and 1T-MoTe2 using FeTe2 and Mo (or MoO3) precursors is presented. Second, a back-gate MoTe2 FET fabrication process is developed, integrating CVD with photolithography, which offers a scalable alternative to exfoliation techniques. The fabrication process utilises a double-layer photolithography method, employing an auxiliary water-soluble resist (SPR92) to protect MoTe2 from damage.

Finally, the electrical performance of the MoTe2 FETs is evaluated, comparing Pd/Au and Ti/Au contact metals. Pd/Au contacts exhibit lower contact resistance (~0.79 MΩ·μm) and form ohmic contacts, while Ti/Au shows higher resistance (~2.06 MΩ·μm) due to a larger Schottky barrier. Both devices demonstrate p-type operation with a mobility of ~2.5 cm²/V·s, though Pd/Au contacts deliver superior performance, including a higher Ion/off ratio (104 ), lower sub-threshold swing (1V/dec), and a threshold voltage of -45 V. These findings suggest that further optimisation of contact metals could improve the performance of p-type MoTe2 FETs for future applications.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Subjects: T Technology > TA Engineering (General). Civil engineering (General); T Technology > TK Electrical engineering. Electronics Nuclear engineering
• Colleges/Schools: College of Science and Engineering > School of Engineering
• Supervisor's Name: Moran, Professor David
• Date of Award: 2024
• Depositing User: Theses Team
• Unique ID: glathesis:2024-84683
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 12 Nov 2024 10:14
• Last Modified: 12 Nov 2024 10:19
• Thesis DOI: 10.5525/gla.thesis.84683
• URI: https://theses.gla.ac.uk/id/eprint/84683

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