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Fabrication of Gate-tunable Graphene Devices for Scanning Tunneling Microscopy Studies with Coulomb Impurities
Published on: July 24, 2015
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Suspending effect on low-frequency charge noise in graphene quantum dot
Xiang-Xiang Song1, Hai-Ou Li1, Jie You1
11] Key Laboratory of Quantum Information, CAS, University of Science and Technology of China, Hefei, Anhui 230026, China [2] Synergetic Innovation Center of Quantum Information &Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
Scientific Reports
|January 31, 2015
Summary
Charge noise in graphene quantum dots (QDs) is significantly higher than in graphene field-effect transistors (FETs). Edge states and impurities, not the substrate, are the primary sources of this noise in graphene QDs.
Area of Science:
- Condensed matter physics
- Materials science
- Quantum electronics
Background:
- Charge noise is a critical factor limiting the performance of gate-controlled quantum dots (QDs).
- Graphene quantum dots (QDs) present unique challenges due to potential influences from substrate interactions and edge states.
- Limited data exists on charge noise characteristics specifically for graphene-based QDs.
Purpose of the Study:
- To investigate and quantify the 1/f charge noise in microscopic graphene quantum dots (QDs).
- To determine the primary origins of 1/f noise in graphene QDs, differentiating between substrate effects, edge states, and surface impurities.
- To compare the noise levels in graphene QDs with those in conventional semiconductor QDs and macroscopic graphene field-effect transistors (FETs).
Main Methods:
- Fabrication and characterization of microscopic graphene quantum dots (QDs).
- Measurement of 1/f noise as a function of temperature and gate voltage around the Coulomb blockade regime.
- Comparison of noise levels between suspended and unsuspended graphene QDs to isolate substrate effects.
- Estimation of potential fluctuations based on noise measurements.
Main Results:
- Microscopic graphene QDs exhibit significantly higher 1/f noise levels compared to macroscopic graphene field-effect transistors (FETs).
- The 1/f noise in graphene QDs increases linearly with temperature.
- Suspending the graphene QD did not substantially alter noise levels, indicating substrate-induced disorder is not the dominant factor.
- Potential fluctuations in graphene QDs were measured to be approximately 1 μeV, an order of magnitude higher than in GaAs/GaAlAs QDs.
- Edge states and surface impurities were identified as the dominant contributors to 1/f noise.
Conclusions:
- Edge states and surface impurities, rather than substrate effects, are the main drivers of 1/f noise in microscopic graphene QDs.
- The substantial charge noise in graphene QDs poses a challenge for the coherence of graphene-based nano-devices.
- Understanding and mitigating this noise is crucial for advancing graphene quantum technologies.
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