Full-chip synthesis and transport characterization of monolayer semiconducting transition metal dichalcogenides
Abstract/Contents
- Abstract
- In recent years, monolayer (1L) semiconducting transition metal dichalcogenides (TMDs) have attracted significant attention for use in a plethora of electronic applications, including logic and memory. However, few studies have examined important metrics for scaling device numbers up and dimensions down for eventual system-level applications. Among the many problems that have been waiting to be solved are demonstration of large area synthesis, description of device-to-device variation, and characterization of velocity saturation. In this work, I will explore these issues principally for 1L MoS2. First, I highlight the recent advancements in solid-source chemical vapor deposition of 1L two-dimensional (2D) semiconductors. I begin by reviewing the theory and conditions necessary for van der Waals epitaxy of large, highly crystalline films of 1L materials. Using this understanding, I establish growth of MoS2, WS2, MoSe2, and WSe2 crystals on SiO2, and perform extensive spectroscopic characterization verifying the quality and integrity of the materials. For MoS2, I also demonstrate an optimized process that yields films large enough (~cm^2) to fabricate thousands of devices simultaneously by optical lithography. Next, I discuss the low-field electrical transport of devices fabricated from these large MoS2 films. In additional to careful measurements revealing the highest mobility (30 to 50 cm^2/V/s) and lowest contact resistance (~1 kΩ∙μm) in any undoped 1L semiconductor, I employ statistical data for devices fabricated on a single, die-sized film to show exceptionally low values for hysteresis (< 5 mV per nm of equivalent SiO2 thickness), and low variation in intrinsic carrier density (~10^11 cm^-2) and drift mobility (~3 cm^2/V/s). I also demonstrate remarkable reliability through bias temperature instability measurements, which constitute an improvement by two orders of magnitude compared to other 2D devices. Finally, I focus on measuring the high-field saturation velocity of electrons in 1L MoS2. A detailed thermal model is used to account for device self-heating, and reveals that devices in high-field operation self-heat by ~200 °C, severely limiting drift velocity. Temperature-dependent measurements subsequently reveal a velocity of 4.3×10^6 cm/s at 295 K, high enough to allow for saturation currents to easily exceed 1.5 mA/μm for digital electronics. This work represents the first evaluation of its kind carried out for 2D electronics, and addresses critical issues to consider for scaling 1L semiconductors for larger applications.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2018 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Smithe, Kirby Kurtis Hayes |
|---|---|
| Associated with | Stanford University, Department of Electrical Engineering |
| Primary advisor | Pop, Eric |
| Thesis advisor | Pop, Eric |
| Thesis advisor | Saraswat, Krishna |
| Thesis advisor | Wong, Hon-Sum Philip, 1959- |
| Advisor | Saraswat, Krishna |
| Advisor | Wong, Hon-Sum Philip, 1959- |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Kirby Kurtis Hayes Smithe. |
|---|---|
| Note | Submitted to the Department of Electrical Engineering. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2018. |
| Location | https://purl.stanford.edu/hw145cm5896 |
Access conditions
- Copyright
- © 2018 by Kirby Smithe
- License
- This work is licensed under a Creative Commons Attribution 3.0 Unported license (CC BY).
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