Substrate level control of the local doping in graphene

Area of Science:

• Materials Science
• Condensed Matter Physics
• Surface Science

Background:

• Graphene's unique electronic properties are sensitive to its substrate.
• Muscovite mica offers an atomically flat surface with electric dipoles, ideal for studying graphene-substrate interactions.
• Understanding substrate effects is crucial for tailoring graphene's electronic behavior.

Purpose of the Study:

• To investigate the influence of muscovite mica's surface features and dipoles on graphene's electronic properties.
• To identify and characterize interfacial phenomena affecting graphene doping.
• To explore the potential for substrate-engineered doping of graphene.

Main Methods:

• Ultrahigh vacuum scanning tunneling microscopy (UHV-STM) for atomic-scale imaging.
• Scanning tunneling spectroscopy (STS) for electronic property measurements.
• Exfoliation of graphene onto muscovite mica substrates.

Main Results:

• Graphene conforms to mica's topography, showing minor modulations.
• Two types of interfacial plateaus were identified: water monolayers and trapped potassium ions.
• Water-induced plateaus lead to graphene insulation or p-type doping nearby.
• Potassium ions induce n-type doping in graphene, with stronger doping directly above the ions.
• Fermi level shifts correlate directly with topographic features, unlike random doping on other substrates.

Conclusions:

• Specific interfacial species (water, potassium ions) on mica enable controlled, localized doping of graphene.
• This substrate-mediated doping mechanism offers a pathway for nanoscopic control over graphene's electronic properties.
• The findings suggest potential applications in designing graphene-based electronic devices with tailored doping profiles.