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Electronic structures and quantum capacitance of twisted bilayer graphene with defects based on three-band
Baojuan Xin1, Kaixin Zou1, Dayong Liu2
1Department of Electronic Science and Engineering, and Tianjin Key Laboratory of Efficient Utilization of Solar Energy, Nankai University, Tianjin 300350, China. lufeng@nankai.edu.cn.
Physical Chemistry Chemical Physics : PCCP
|March 12, 2024
Summary
Introducing a new three-band model for twisted bilayer graphene (tBLG) with carbon (C) vacancies significantly enhances quantum capacitance. This model accurately captures electronic structures, improving device performance for low-power applications.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Computational Physics
Background:
- Twisted bilayer graphene (tBLG) exhibits unique electronic properties, but accurately modeling the impact of defects like carbon (C) vacancies on its low-energy physics remains challenging.
- Existing single-band models fail to capture the complex behavior of C-vacancies in tBLG, limiting theoretical understanding and material design.
- Carbon vacancies are known to influence the density of states (DOS) and quantum capacitance, crucial parameters for electronic device applications.
Purpose of the Study:
- To develop and validate a more accurate three-band tight-binding model for twisted bilayer graphene (tBLG) with carbon (C) vacancies.
- To investigate the modulation mechanism of C vacancies on the electronic structures, specifically the density of states (DOS) around the Fermi level (EF), and quantum capacitance of tBLG.
- To provide theoretical insights for designing advanced electrode materials with enhanced quantum capacitance for low-power electronic devices.
Main Methods:
- Development of a three-band tight-binding model incorporating three p orbitals of carbon atoms to describe tBLG with C vacancies.
- Parameterization of hopping integrals for the proposed three-band tight-binding model.
- Simulation and analysis of electronic structures and quantum capacitance of tBLG at a specific twist angle (1.47°) under varying C vacancy concentrations.
Main Results:
- The three-band model accurately captures the low-energy physics of tBLG with C vacancies, unlike simpler models.
- Impurity states induced by C vacancies around the Fermi level (EF) and interlayer hopping lead to band splitting.
- Quantum capacitance significantly increases from ~18.82 μF cm-2 in pristine tBLG to ~172.76 μF cm-2 at zero bias in tBLG with C vacancies.
- The working window for high quantum capacitance is broadened at low voltages, and capacitance further increases with higher vacancy concentrations.
Conclusions:
- The proposed three-band tight-binding model is suitable for describing tBLG with C vacancies, offering improved accuracy over single-band models.
- Carbon vacancies substantially enhance the density of states (DOS) around the Fermi level (EF), leading to a significant improvement in quantum capacitance.
- These findings offer valuable theoretical guidance for the development of next-generation electrode materials for energy-efficient electronic devices.
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