Tunable graphene doping by modulating the nanopore geometry on a SiO₂/Si substrate.

Area of Science:

• Materials Science
• Nanotechnology
• Solid-State Physics

Background:

• Graphene field-effect transistors (G-FETs) are crucial for next-generation electronics.
• Controlling graphene doping is essential for optimizing G-FET performance.
• Existing doping methods often lack tunability and can introduce hysteresis.

Purpose of the Study:

• To introduce a tunable graphene doping method using nanoporous (NP) SiO2/Si substrates.
• To investigate the effect of substrate nanoporosity on G-FET characteristics.
• To analyze the mechanisms behind doping and hysteresis in G-FETs fabricated on NP substrates.

Main Methods:

• Fabrication of NP SiO2/Si substrates with controllable pore size and pitch using laser interference lithography (LIL).
• Fabrication of bottom-contact G-FETs on both NP and flat SiO2/Si substrates.
• Characterization of graphene doping and G-FET performance using Raman spectroscopy and transfer curve measurements.

Main Results:

• Graphene on NP substrates exhibited n-doped behavior, indicated by a blue-shift in Raman spectra.
• Dirac voltage shifts correlated with substrate porosity, demonstrating tunable doping.
• Reduced hysteresis was observed for G-FETs on NP substrates with smaller pores and lower porosity.

Conclusions:

• The developed NP SiO2/Si substrate offers a tunable method for graphene doping.
• Electrostatic doping effects, influenced by substrate capacitance and porosity, are key to performance modulation.
• The NP substrate approach effectively reduces hysteresis in G-FETs, paving the way for more stable devices.