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6CCVD Research

Schemes for Single Electron Transistor Based on Double Quantum Dot Islands Utilizing a Graphene Nanoscroll, Carbon Nanotube and Fullerene

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2022-01-04
JournalMolecules
AuthorsVahideh Khademhosseini, Daryoosh Dideban, Mohammad Taghi Ahmadi, Hadi Heidari
InstitutionsUniversity of Kashan, University of Glasgow
Citations4
AnalysisFull AI Review Included

Executive Summary

Section titled “Executive Summary”

This research focuses on improving Single Electron Transistor (SET) performance by utilizing double quantum dot islands composed of hybrid carbon nanomaterials: Graphene Nanoscroll (GNS) combined with Carbon Nanotube (CNT) or Fullerene (C60).

  • Performance Enhancement: The GNS-CNT SET configuration demonstrated superior performance, achieving higher drain-source current (Ids) and significantly lower Coulomb Blockade (CB) range compared to the GNS-C60 SET.
  • Modeling Approach: Device current was successfully modeled using a combination of Schrödinger’s equation and the Landauer formalism, implemented via MATLAB and validated using Atomistix ToolKit (ATK) simulations.
  • Geometric Optimization: Increasing the GNS length (up to 5 nm) or GNS spiral length (up to 84 nm) resulted in thinner tunnel barriers, leading to faster electron tunneling and increased current output.
  • Thermal Dependence: Current increased significantly with ambient temperature, peaking at 300 K, while higher temperatures simultaneously decreased the Coulomb blockade range.
  • Charge Stability: Quantitative analysis of charge stability diagrams showed that the GNS-CNT device had a total Coulomb diamond area (0.366 V2) substantially smaller than the GNS-C60 device (1.372 V2), confirming its higher conductance.
  • Core Mechanism: The improved performance is attributed to the optimized geometry (larger island size, thinner tunnel barriers) and the specific shape of the GNS-CNT island, which increases the number of available states for electron tunneling.

Technical Specifications

Section titled “Technical Specifications”
ParameterValueUnitContext
Operating Temperature Range100 to 300KCurrent increases significantly with temperature.
Applied Gate Voltage (Vg) Range1 to 3mVCurrent increases with Vg, shifting the first unoccupied energy level.
Drain-Source Voltage (Vds) Range-5 to 5mVTested range for I-V characteristics.
Optimal GNS Length5nmYields highest current and lowest Coulomb blockade range.
Optimal GNS Spiral Length84nmYields highest current due to thinnest tunnel barrier.
Optimal GNS Turns20-Lowest number of turns resulted in largest island size and highest current.
Carbon-Carbon Bond Length (ac-c)1.42AngstromUsed in transmission coefficient calculations.
Total Coulomb Diamond Area (GNS-CNT)0.366V2Indicates higher conductance (smaller zero-voltage region).
Total Coulomb Diamond Area (GNS-C60)1.372V2Indicates lower conductance (larger zero-voltage region).
Max Current (GNS-CNT, 300 K, 3 mV Vg)~0.6”AHighest simulated current output (Figure 11b).
Max Current (GNS-C60, 300 K, 3 mV Vg)~0.35”AHighest simulated current output (Figure 11a).

Key Methodologies

Section titled “Key Methodologies”

The study relied on theoretical modeling and simulation to analyze the double quantum dot SET structures.

  1. Device Structure Design:

    • Two double quantum dot SETs were designed using Atomistix ToolKit (ATK) software: GNS-C60 SET and GNS-CNT SET.
    • Both islands were designed to contain an equal number of carbon atoms (96 atoms) for comparative analysis.

  2. Current Modeling (Schrödinger/Landauer Formalism):

    • The SET structure was divided into five regions: two potential wells (the islands) and three tunnel junctions.
    • Schrödinger’s equation was solved for each region to determine the electron wave functions (Κn(x)).
    • Boundary conditions were applied to solve for the constant coefficients (A, B) and calculate the transmission coefficient T(E) for the GNS, C60, and CNT islands individually.
    • The total transmission coefficient T1(E) or T2(E) for the double-island SET was calculated as the product of the individual island transmission coefficients.

  3. I-V Characteristic Derivation:

    • The drain-source current (Ids) was calculated using the Landauer formalism, integrating the transmission coefficient T(E) and the Fermi probability function F(E) over the electron energy range.
    • MATLAB codes were implemented to plot Ids versus Vds under varying parameters (GNS length, spiral length, number of turns, temperature, and gate voltage).

  4. Charge Stability Diagram Simulation:

    • Charge stability diagrams were generated using the Atomistix ToolKit (ATK) software.
    • The Density Functional Theory (DFT) method, specifically using the Local-Density Approximation (LDA), was selected for the simulation of charge states.
    • These diagrams were used to extract quantitative data on Coulomb diamond areas and Coulomb blockade ranges (Table 1).

Commercial Applications

Section titled “Commercial Applications”

The enhanced performance characteristics (high speed, low power, high sensitivity) of the GNS-CNT SET make it suitable for next-generation nanoscale electronic devices.

  • Quantum Information Processing: SETs function as highly sensitive charge sensors, critical for reading out the state of quantum dots in silicon or carbon-based quantum computing architectures.
  • Advanced Memory (SET Memory): Utilization in single electron memory devices, offering ultra-low power consumption and high integration density for future non-volatile storage.
  • High-Frequency Oscillators: SETs can be used in nanoscale oscillators due to their fast electron tunneling speeds, as explicitly mentioned in the literature.
  • Chemical and Gas Sensing: The high sensitivity of SETs to changes in the local electrostatic environment makes them ideal for detecting specific gas molecules (e.g., CO, NO) or chemical species at the nanoscale.
  • Low-Power Electronics: The inherent low leakage current and reduced power consumption associated with SET operation are crucial for developing energy-efficient integrated circuits and portable electronics.
View Original Abstract

The single electron transistor (SET) is a nanoscale switching device with a simple equivalent circuit. It can work very fast as it is based on the tunneling of single electrons. Its nanostructure contains a quantum dot island whose material impacts on the device operation. Carbon allotropes such as fullerene (C60), carbon nanotubes (CNTs) and graphene nanoscrolls (GNSs) can be utilized as the quantum dot island in SETs. In this study, multiple quantum dot islands such as GNS-CNT and GNS-C60 are utilized in SET devices. The currents of two counterpart devices are modeled and analyzed. The impacts of important parameters such as temperature and applied gate voltage on the current of two SETs are investigated using proposed mathematical models. Moreover, the impacts of CNT length, fullerene diameter, GNS length, and GNS spiral length and number of turns on the SET’s current are explored. Additionally, the Coulomb blockade ranges (CB) of the two SETs are compared. The results reveal that the GNS-CNT SET has a lower Coulomb blockade range and a higher current than the GNS-C60 SET. Their charge stability diagrams indicate that the GNS-CNT SET has smaller Coulomb diamond areas, zero-current regions, and zero-conductance regions than the GNS-C60 SET.

Tech Support

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 2017 - Single Electron Transistor with Single Aromatic Ring Molecule Covalently Connected to Graphene Nanogaps [Crossref]
  2. 2020 - Room temperature single electron transistor based on a size-selected aluminium cluster [Crossref]
  3. 1987 - Observation of single-electron charging effects in small tunnel junctions [Crossref]
  4. 2000 - Nano mechanical oscillations in a single-C60 transistor [Crossref]
  5. 2017 - Single-electron tunneling through an individual arsenic dopant in silicon [Crossref]
  6. 1986 - Coulomb blockade of single-electron tunneling, and coherent oscillations in small tunnel junctions [Crossref]
  7. 2002 - Coulomb blockade and the Kondo effect in single-atom transistors [Crossref]
  8. 2003 - Coulomb blockade, single-electron transistors and circuits in silicon [Crossref]
  9. 2020 - Single-electron current gain in a quantum dot with three leads [Crossref]
  10. 2021 - Carbon single-electron point source controlled by Coulomb blockade [Crossref]

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