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Advanced Experimental Methods for Low-temperature Magnetotransport Measurement of Novel Materials
Published on: January 21, 2016
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Insulator-quantum Hall transitionin monolayer epitaxial graphene
Lung-I Huang1, Yanfei Yang2, Randolph E Elmquist3
1National Institute of Standards and Technology (NIST), Gaithersburg, MD 20899, USA; Department of Physics, National Taiwan University, Taipei 106, Taiwan.
RSC Advances
|December 7, 2016
Summary
Magneto-transport measurements reveal temperature-independent insulator-quantum Hall transitions in epitaxial graphene. This contrasts with the absence of such transitions in mechanically exfoliated graphene, highlighting material preparation
Area of Science:
- Condensed Matter Physics
- Materials Science
- Nanotechnology
Background:
- Epitaxial graphene on SiC offers a platform for studying fundamental electronic properties.
- Understanding the insulator-quantum Hall (I-QH) transition is crucial for solid-state physics.
- The role of disorder and substrate on graphene's electronic behavior remains an active research area.
Purpose of the Study:
- To investigate the magneto-transport properties of low-density, large-area monolayer epitaxial graphene.
- To identify signatures of the insulator-quantum Hall (I-QH) transition in these devices.
- To compare the observed phenomena with graphene prepared via mechanical exfoliation.
Main Methods:
- Magneto-transport measurements were performed on monolayer epitaxial graphene grown on SiC.
- Longitudinal resistivity (ρxx) and Hall conductivity (σxy) were analyzed as a function of temperature and magnetic field.
- Data was converted to longitudinal conductivity (σxx) and Hall conductivity (σxy) to analyze the flow diagram.
Main Results:
- Temperature-independent crossing points in longitudinal resistivity, indicative of the I-QH transition, were observed in all devices.
- A temperature-driven flow diagram, approximated by the semi-circle law, and a temperature-independent point in Hall conductivity near e²/h were observed in the most disordered device.
- Strongly insulating behavior was observed, contrasting with metallic behavior and the absence of the I-QH transition in graphene on SiO₂ prepared by mechanical exfoliation.
Conclusions:
- Epitaxial graphene on SiC exhibits characteristics of the insulator-quantum Hall transition.
- The observed phenomena are linked to the evolution of the zero-energy Landau level at low magnetic fields.
- Substrate and preparation method significantly influence the electronic transport properties and the occurrence of the I-QH transition in graphene.
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