Recent progress in layered transition metal dichalcogenides (TMDs) has led to various promising electronic and optoelectronic applications. However, the structure of materials plays a critical role in electronic and optoelectronic devices, and determines performance. Electronic and optoelectronic devices typically consist of multiple layers that form electrical homojunctions or heterojunctions. Therefore, in a device it can be expected that a WS2 layer may serve as the substrate for a subsequent layer in a multilayer device stack and determine how the layer grows. In transistor structures, roughness at the channel/gate dielectric interface introduces field variations and charge scattering. Therefore, understanding the relations between processing, surface morphology and properties is important.
In this project, the effects of pulsed laser deposition (PLD) processing conditions on the surface morphology of few layered WS2 films were studied. WS2 films were synthesized under processing conditions that represent the extremes of surface supersaturation and kinetic energy transfer from the flux to the growing films, and evolution of the surface morphology was studied. The specific conditions were 1Hz/50mJ, 10Hz/50mJ, 1Hz/300mJ, and 10Hz/300mJ respectively. Combining AFM, XRD and Raman analyses, it was determined that deposition at 10Hz/300mJ, provided the best structural properties and surface morphology. Growth appeared to be 3D-cluster, and was governed by supersaturation rather than by surface diffusion processes. No clear correlation between mobility and surface roughness was found. Hall measurements and XPS data show the highest mobility was obtained with the highest S/W ratio, indicating that point defect scattering rather than scattering from surface roughness was dominant.
| Identifer | oai:union.ndltd.org:unt.edu/info:ark/67531/metadc1505277 |
| Date | 05 1900 |
| Creators | Cai, Bimin |
| Contributors | Shepherd, Nigel, Reidy, Rick F., Bouanani, Mohamed El |
| Publisher | University of North Texas |
| Source Sets | University of North Texas |
| Language | English |
| Detected Language | English |
| Type | Thesis or Dissertation |
| Format | vii, 38 pages, Text |
| Rights | Use restricted to UNT Community, Cai, Bimin, Copyright, Copyright is held by the author, unless otherwise noted. All rights Reserved. |
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