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Nanosheet thickness-modulated MoS2 dielectric property evidenced by field-effect transistor performance
Sung-Wook Min1, Hee Sung Lee, Hyoung Joon Choi
1Department of Physics, Yonsei University, Seoul 120-749, Korea.
Nanoscale
|December 13, 2012
Summary
Investigating molybdenum disulfide (MoS2) field-effect transistors (FETs), this study reveals that thinner MoS2 nanosheets enhance device performance. Thicker MoS2 layers increase dielectric constant, reducing benefits from high-k dielectrics.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Nanotechnology
Background:
- Molybdenum disulfide (MoS2) is a promising 2D material for next-generation electronics.
- Field-effect transistors (FETs) based on MoS2 are under intense research for improved performance.
- Device performance is significantly influenced by material thickness and dielectric properties.
Purpose of the Study:
- To investigate the impact of MoS2 nanosheet thickness on the performance of top-gate FETs.
- To correlate MoS2 thickness with its dielectric constant and its effect on device characteristics.
- To compare the performance of top-gate and bottom-gate MoS2 FETs.
Main Methods:
- Fabrication of top-gate MoS2 nanosheet FETs with varying MoS2 layer numbers (single, double, triple).
- Utilized Al2O3 (high-k dielectric) for top-gate structures and SiO2 for bottom-gate structures.
- Characterization of device performance, including mobility and subthreshold swing (SS).
Main Results:
- Top-gate MoS2 FETs with Al2O3 exhibited significantly higher mobility compared to bottom-gate FETs with SiO2.
- Single-layered MoS2 FETs showed the highest mobility (~170 cm^2 V^-1 s^-1) and lowest SS (90 mV dec^-1).
- Device performance degraded with increasing MoS2 thickness, with double- and triple-layered FETs showing lower mobility and higher SS.
Conclusions:
- MoS2 nanosheet thickness critically affects FET performance, with thinner layers yielding superior results.
- The increased dielectric constant of thicker MoS2 layers diminishes the advantages of high-k top-gate dielectrics.
- Optimizing MoS2 thickness is crucial for maximizing the performance of MoS2-based electronic devices.
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