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Modeling the Field Emission Enhancement Factor for Capped Carbon Nanotubes Using the Induced Electron Density
Caio P de Castro1, Thiago A de Assis1, Roberto Rivelino1
1Instituto de Fı́sica , Universidade Federal da Bahia , Campus Universitário da Federação, Rua Barão de Jeremoabo s/n , 40170-115 , Salvador , BA Brazil.
Journal of Chemical Information and Modeling
|December 4, 2019
Summary
Quantum mechanical calculations using Density Functional Theory (DFT) reveal that field enhancement factors (FEFs) in capped single-walled carbon nanotubes (SWCNTs) are constant and independent of the applied macroscopic field. This finding aligns with experimental observations in field electron emission.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Quantum Chemistry
Background:
- Field electron emission from single-walled carbon nanotubes (SWCNTs) is crucial for various electronic devices.
- Experimental studies show constant field enhancement factors (FEFs) for capped SWCNTs, independent of the applied macroscopic field (FM).
- Classical electrostatic models provide insights but lack quantum mechanical rigor.
Purpose of the Study:
- To reconcile experimental observations of constant FEFs with quantum mechanical calculations.
- To investigate the electronic properties and field enhancement behavior of capped SWCNTs using Density Functional Theory (DFT).
- To analyze the influence of SWCNT structure on potential energy barriers and field emission characteristics.
Main Methods:
- Density Functional Theory (DFT) calculations were employed to model two capped SWCNTs: (6,6) and (10,0).
- Simulations analyzed local induced field enhancement factors (FEFs) at the SWCNT apex under varying macroscopic fields (FM).
- Quantum mechanical potential energy (PE) barriers were computed along the SWCNT axis and near the apex.
Main Results:
- Apex values of local induced FEF were found to be similar for both SWCNT structures and independent of FM.
- Calculated FEFs closely matched values predicted by classical conductor models.
- Potential energy barrier profiles showed structural-specific differences, even at zero macroscopic field, indicating chemically induced charge transfers.
Conclusions:
- Quantum mechanical calculations successfully reproduce the experimentally observed constant FEFs in capped SWCNTs.
- Induced FEF values are linked to the longitudinal polarizability of the SWCNT system.
- Structure-specific potential energy landscapes at the SWCNT apex suggest intrinsic electronic properties influencing field emission.
